Millimeter Wave Grid Oscillators
Author(s):
David B. Rutledge;
Zorana B. Popovic;
Moonil Kim
Show Abstract
Loading a two-dimensional grid with active devices offers a means of combining the power of solid-state oscillators in the microwave and millimeter-wave range. The grid structure allows a large number of negative resistance devices to be combined. In this approach, the combining is done in free space, and the active devices do not require an external locking signal. The loaded grid is a planar structure amenable to monolithic integration. Measurements on a 25-MESFET grid at 9.7 GHz show power-combining and frequency-locking without an external locking signal, with an ERP of 37W. Experimental far-field patterns agree with theoretical results obtained using reciprocity.
A Feedback Model Of Millimetre Wave Harmonic Oscillators And Its Application
Author(s):
Jinping Xu;
Sifan Li
Show Abstract
In this paper a feedback model of second harmonic oscillators is developed. By using describing functions of nonlinearity of active devices, the performances of second harmonic oscillators are studied. Frequency dependence of I-V characteristics of active element are taken into account. The ratio of maximum output power of second harmonic to fundamental is given. The maximum harmonic locking bandwidth of injected harmonic oscillator is derived. The theoretical prediction is compared with experimental results.
Time Dependent Simulation Of The Quantum Well Injection Transit Time Diode
Author(s):
D. R. Miller;
V. P. Kesan;
R. L. Rogers;
C. M. Maziar;
D. P. Neikirk
Show Abstract
The quantum well injection transit time (QWITT) diode is a transit time device that couples a heterojunction barrier structure as an injector with a depleted epitaxial drift region, as shown in Figure 1. The device, which was originally proposed by Kesan et al. [1], is a promising solid state source with potential for operation at the higher millimeter wave frequencies. Both large and small signal analyses of the device have shown that the specific negative resistance due to transit time effects from the drift region are on the order of, or are significantly greater than, the intrinsic negative differential negative resistance of the quantum well double barrier diode. This paper presents results of a large signal simulation which uses a full set of semiconductor time dependent transport equations, and solves self-consistently for the electric field as well as for the electron and hole populations throughout the device.
Power Combining Fet Oscillator Using Coupled Rampart Line Antennas
Author(s):
Joel Birkeland;
Tatsua Itoh
Show Abstract
Circuits in which oscillators are integrated with antennas to form quasi-optical sources have applications in phased array radar (1), quasi-optical local oscillators (2), and a variety of obstruction detection and process control applications (3). In this paper we describe a low-cost planar oscillator circuit in which 2 FETs are coupled by microstrip rampart line antennas and operate in a push-pull power combining configuration. Prototype circuits have been constructed which operate at X-band; the same principle may be applied at higher frequencies.
A 94/47GHz Freqency Halver Using A Ga As Gunn-Device
Author(s):
Helmut Barth
Show Abstract
Basically, frequency division is possible by synchronizing a harmonic mode oscillator at its harmonic frequency fH while coupling out the fundamental frequency fF. However, the very high virtually external 0-factor (>1000 c.o. [1]) of standard type harmonic mode oscillators limits the bandwidth of operation to only a few hundred MHz at moderate input power levels.
Parametric Analysis Of Galnas Devices For Mm-Wave Applications
Author(s):
A. R. Jha
Show Abstract
Metal-Insulator-Semiconductor FETs (MISFETs) when fabricated from GalnAs semiconductor material offer significant performance improvement at mm-wave frequencies. Higher electron velocity, power-added efficiency, device stability, transconductance and resistance to ionizing radiation are the outstanding features of these devices. Significant improvements in gain-bandwidth product, AM/PM performance, and third-order intermodulation distortion make GalnAs devices attractive for communication and radar equipment.
Advanced Lightwave Technology - Very Large Capacity Optical Coherent Communications
Author(s):
Kiyoshi Nosu
Show Abstract
Attempts are recommencing, after a ten year dormancy, to use lightwaves in as sophisticated manner as that in which radio waves are used. Technologies previously developed for radio wave systems are now being transferred to high speed/large capacity advanced lightwave communications. This paper reviews key technologies for advanced lightwave communications, especially optical heterodyne/homodyne detection and optical FDM ( frequency division multiplexing). 1.INTRODUCTION Almost one hundred years have passed since Marconi invented radio communication, and about thirty years have passed since the invention of the laser. Present practical fiber optic communication systems convey information by changing optical "power". In other words, present optical communications are at the level of spark discharge radio communications in the 1890'. With the recent development of coherent light sources, more sophisticated communication technologies which utilize the very large bandwidth potential of optical carriers are becoming feasible (1)-(4). Advanced lightwave technologies using coherent light sources have potential for constructing large capacity communication systems, breaking through the present barrier of incoherent light communication performance. There are two ways to improve transmission capacity : (1) high speed transmission - time division multiplexing, and (2) multi-channel optical transmission - optical frequency division multiplexing. A key technology in high-speed transmission is optical heterodyne detection., and a key technology in optical multiplexing transmission is optical frequency division multiplexing ( optical FDM). This paper describes the present state and perspectives of these advanced lightwave technologies. 2.HETRODYNE DETECTION TECHNOLOGY A block diagram of a communication system using heterodyne detection is shown in Fig.1. Figure 2 shows theoretical estimations of high speed transmission system repeater spans. The combination of FSK or PSK modulation and optical heterodyne detection permits significantly improved sensitivity , improved by more than 15dB over conventional direct detection.
Microwave Modulation Of Light
Author(s):
Tadasi Sueta
Show Abstract
High-speed or wide-band light modulators are described. It is shown that high-performance microwave light modulators are realized with the optical guided-wave structure and traveling-wave type operation. The integration of high-performance modulators is also discussed. Other topics include the efficient light modulation at millimeter-wave frequencies and the generation of extremely broad optical sideband (0.64 THz) by a microwave light modulator.
Generation And Detection Of Millimeter Wave Modulated Light With High Speed Diode Lasers And Photodetectors
Author(s):
J. E. Bowers;
C. A. Burrus;
F. G. Storz
Show Abstract
The bandwidths of semiconductor lasers, modulators and photodetectors have dramatically increased recently, making it possible to directly modulate light with signals whose frequencies extend from dc to millimeter wave frequencies. Furthermore, the low attenuation of optical fiber and modulation-frequency-independent nature of the attenuation makes lightwave transmission of broadband microwave signals attractive. Recent advances in generating subpicosecond optical pulses at microwave frequencies using semiconductor lasers has made it possible to generate combs of frequencies extending through the entire microwave and millimeter wave spectrum. With present and next generation photodetectors to detect these optical signals, many applications of optoelectronic devices to spectroscopy, analog and digital transmission, electro-optic sampling, and high speed electronics and optical computing have become important.
Optically Controlled Millimeter Wave Phased Array Antennas.
Author(s):
P. R. Herczfeld;
A. S. Daryoush
Show Abstract
This paper is concerned with recent developments related to optically controlled phased array antennas operating in the millimeter wave range. The antenna consists of three main elements: the central processing unit (CPU), the fiberoptic (FO) distribution system with optical signal processing capability, and the planar array. The antenna array is composed of a large number of distributed and independently powered transmit/receive (T/R) modules fabricated by monolithic microwave integrated circuit (MMIC) techniques. The function of the fiber optic distribution system is to distribute the carrier reference signals for the frequency synchronization of the T/R modules, to transmit the appropriate control signals for beam forming, and to route the information and data signals.
GaAs Traveling-Wave Optical Modulator Using A Modulated Coplanar Strip Electrode With Periodic Cross-Tie Overlay
Author(s):
H.-Y. Lee;
T. Itoh
Show Abstract
This paper proposes and analyzes a GaAs traveling-wave optical modulator which uses a modulated coplanar strip electrode with periodic cross-tie overlay. This slow-wave structure can be designed to satisfy phase velocity and impedance matching conditions simultaneously. The dominant conductor loss in the slow-wave structure is reduced using the modulated coplanar strip electrode. The calculated modulation bandwidth is much wider than those of conventional electrode structures which are limited by phase velocity mismatch.
A New Class Of Scannable Millimeter Wave Antennas
Author(s):
Arthur A. Oliner
Show Abstract
The complexity usually associated with scanning arrays at millimeter wavelengths produces fabrication difficulties, so that alternative methods are needed that employ simpler structures. This paper describes such an alternative scanning approach, and presents a group of new and simpler radiating structures suitable for millimeter-wave applications.
Integrated Circuit Active Antenna Elements And Spatial Power Combining
Author(s):
Kai Chang
Show Abstract
Recent developments in microwave/millimeter-wave solid-state devices and integrated circuits have made it possible to integrate the active sources directly with planar antennas. The circuits have advantages of low cost, small size and monolithic implementation. This paper summarizes the recent results, potential applications and future trends of active antenna elements.
Detector Antenna Array With A Dielectric Lens For Millimeter-Wave Imaging
Author(s):
Kazuhiro Uehara;
Takeshi Yonekura;
Hiroshi Nishimura;
Koji Mizuno;
David B. Rutledge
Show Abstract
We are developing antenna arrays as detectors for millimeter-wave imaging. The antenna is a resonant dipole [1] with a director in a dielectric lens. Our goal is to measure the plasma density of the TSUKUBA GAMMA-10 plasma machine.
Omnidirectional Periodic Rod Antenna - Tmon Mode Excitation
Author(s):
Xu Shanjia
Show Abstract
An Omni-directional periodic dielectric rod antenna operating in TMon mode is investigated. As an eigenvalue problem, the structure is analyzed theoretically with mode matching technique. The radiation characteristics are calculated for different parameters with a particular attention directed to the Brewster angle effect on the performaces of the antenna.
Efficiency Of Millimeter-Wave Horn Imaging Arrays
Author(s):
Gabriel M. Rebeiz;
Yong Guo;
Philip A. Stimson;
David B. Rutledge
Show Abstract
Two-dimensional horn-antenna arrays are monolithic, high-efficiency imaging detectors of millimeter-wave radiation. In this configuration, a dipole antenna is suspended in a pyramidal horn on a 1-μm silicon oxynitride membrane. This approach leaves room on the wafer for low-frequency lines and processing electronics. Antenna pattern measurements on single elements agree well with theory, exhibiting 3-dB beamwidths of 54° and 62° for the E and H-planes respectively. Horn aperture efficiencies of 44 ± 4% have been measured at 93 GHz. Loss processes include impedance mismatch loss, due to impedance mismatch between the antenna and the detector, resistive loss in the horn sidewalls, cross-polarization, intrinsic pattern loss, and horn-to-horn coupling loss. A system efficiency of 24% has been measured for a lens-coupled array.
Antennas On Layered Substrates
Author(s):
R. L. Rogers;
D. P. Neikirk;
H. Ling;
T. Itoh
Show Abstract
Electrically thick layered substrates using the resonant structures discussed in [2-4] offer the advantage of providing simple and efficient support for millimeter wave printed circuit antennas. They can also produce desirable beam patterns through the proper choice of dielectrics. There has been theoretical study of these layered structures [2-4], but experimental investigation has been limited. Also, the primary focus has been on the use of dipole antennas with these structures, while slot antennas have received little attention. Here we give results for efficiency calculations for both slots and dipoles, and experimental pattern measurements for slots on layered substrates which show that they can produce desirable beam patterns with high front-to-back ratio. We find good agreement between theory and lOGHz modeling experiments.
New Directions In Mmw Vacuum Electronics Research
Author(s):
R. J. Barker
Show Abstract
A technical review and appraisal of ongoing basic research in vacuum and plasma mm-wave sources sponsored by the Air Force Office of Scientific Research (AFOSR) will be presented. In all, the work of more than a dozen leading scientific laboratories will be discussed. Emphasis will be placed on individual project goals, recent results, and important technical issues.
Short Period Wiggler Free Electron Laser With A Sheet Electron Beam
Author(s):
J. H. Booske;
D. J. Radack;
T. M. Antonsen,Jr.;
W. W. Destler;
J. M. Finn;
V. L. Granatstein;
P. E. Latham;
I. D. Mayergoyz;
J. Rodgers;
E. T. Rosenbury
Show Abstract
A review of recent progress at the University of Maryland's Laboratory for Plasma Research (LPR) on the development of millimeter-wave free electron lasers (FELs) using short period electromagnet planar wigglers and low voltage (Vbeam ≈ 500kV) sheet electron beams will be given.
Tunable Micro-Undulators For Free Electron Lasers
Author(s):
S. C. Chen;
G. Bekefi;
S. DiCecca;
R. Temkin
Show Abstract
We present the test results of a novel microwiggler structure [1] for free-electron lasers, in which, each 2.4 mm period consists of two channels of miniature electro magnets energized by current with opposite polarities. The magnetic field in each half-period is independently controllable and the tunability is demonstrated experimentally, which may provide means for reducing random field errors; for field tapering; for optical klystron configurations; and for electron beam injection.
Collectre Instability In Circular Free Electron Laser
Author(s):
Yasushi Kawai;
Hirobumi Saito;
Jonathan S. Wurtele
Show Abstract
An analytical fluid theory is developed for a circular free electron laser, including the effect of the space charge wave. The dispersion relation of the FEL radiation and the space charge wave is analytically obtained. It is found that the space charge wave gives strong effect on the performance of a circular FEL.
Suppression Of Sidebands By Diffraction In A Free-Electron Laser
Author(s):
T. M. Antonsen. Jr.;
G. Laval
Show Abstract
The stability of sidebands in a free electron laser is determined in the regime in which the three-dimensional structure of the modes is important. It is found that the growth rate of the sidebands in the presence of a fundamental mode which is weakly guided by the beam is reduced. The indications are that for some parameters the spatial growth rate of the sidebands can be made less than that of the fundamental.
Analysis And Nonlinear Simulation Of Quadrupole And Dipole Wiggler Fels For Millimeter Waves
Author(s):
J. E. Scharer;
S. F. Chang;
O. C. Eldridge
Show Abstract
An FEL amplifier with a helical quadrupole wiggler is investigated analytically and numerically. A 3-D simulation code is utilized to examine the nonlinear evolution of circular waveguide modes as well as the characteristics of relativistic particle motion, which illustrate a strong focussing effect. The simulation predicts a 0.55 dB/cm gain, 2% efficiency, and 8% bandwidth for the optimum TE21 mode at 300 GHz for an untapered wiggler. Mode competition for an over-moded waveguide and a nonlinear wiggler taper for efficiency enhancement are examined for a linear dipole wiggler in a rectangular guide. It is found that the maximum TEoi mode efficiency is 53% at 280 GHz and that the TM21 mode power can be as high as 28% in the uniform wiggler region.
Development Of High Efficiency Frequency Multipliers For 130-350 GHz
Author(s):
Timo Tolmunen;
Antti Raisanen;
Mikko Sironen
Show Abstract
In this research the feasibility of developing high efficiency mm-wave multipliers in the frequency range of 130-350 GHz has been studied. A frequency quadrupler for 140 GHz, frequency doublers for 183 GHz and 230 GHz and a frequency tripler for 345 GHz have been analyzed and optimized. The development of high efficiency frequency multipliers is especially important for the spaceborne mm-wave and submm-wave heterodyne receivers used for radio astronomy and remote sensing of the atmosphere.
Periodic Monolithic Millimeter-Wave Quantum Well Oscillator
Author(s):
A. Mortazawi;
V. P. Kesan;
D. P. Neikirk;
T. Itoh
Show Abstract
A small-signal and large-signal analysis of a traveling wave structure implemented by periodically loading a parallel-plate waveguide with QWITT diodes is presented. The analysis starts with a self-consistent, large-signal model for the diode. The diode model is then coupled to a model for the waveguide circuit and solved using the harmonic balance technique. The output power as a function of frequency for three harmonics for a QWITT oscillator is determined. Our results emphasize the importance of obtaining the ac voltage modulation self-consistently from the circuit when calculating the output power obtained from a QWITT oscillator. The oscillation frequency of the multiple-diode circuit is determined primarily by the periodicity of the structure. The physical dimensions of the waveguide facilitate monolithic fabrication of the oscillator circuit.
Rigorous Field Analysis Of Impedances Of Sys Milliiienal Wave Oscillare Cavities
Author(s):
Wei Hong;
Sifan Li
Show Abstract
This paper presents a generalized field analysis method for calculating the external circuit impedances looking outside from the active devices of some millimeter wave oscillators. For a simple oscillator model with a radial disc and a diode existing in a rectangular waveguide, the numerical results are in agreement with the experimental data. Impedance characteristics for several different oscillator configruations are given, and sane useful conclusions for oscillator design are derived.
Theory Of The Diocotron Instability In High Power Magnetron
Author(s):
Han S. Uhm;
H. C. Chen;
Howard E. Brandt
Show Abstract
Diocotron stability properties in a relativistic electron flow generated inside high power magnetrons are investigated within the framework of a linearized macroscopic cold fluid model. A massless guiding-center approximation has been made in this theoretical calculation to be analytically tractable. Closed algebraic dispersion relations obtained in this article are fully relativistic and fully electro-magnetic. Influence of the anode resonator effects are also fully incorporated. Numerical investigation of the dispersion relation is carried out for a broad range of system parameters and results will be presented.
Power Combining System Using Two Push Pull Power Amplifiers
Author(s):
Sachihiro Toyoda
Show Abstract
This paper describes a power combining system using two push-pull power amplifiers. Power amplifiers using two different type phase inverter were proposed and tested at 5-GHz band. Bandwidth of these power combining systems were 1.65 GHz and 1.8 GHz, respectively, and either of their output power were 14.5 W.
Quasi-Optical Resonator Far Millimeter And Submibimeter Wave Solid-State Sources
Author(s):
Morishige Hieda;
Masatoshi Nakayama;
Koji Mizuno;
Toshihiro Ajikata;
David B. Rutledge
Show Abstract
A new cavity for millimeter and submillimeter wave solid-state oscillators is demonstrated. The resonator consists of a Fabry-Perot resonator with a grooved mirror. It has a capability for power com-bining. Experimental results from X-band models of the resonator are presented. Frequency-locking and power-combining with six Gunn diodes are demonstrated.
Numerical Simulation Of The Diocotron Instability In Planar Diode Geometry
Author(s):
H. C. Chen;
H. S. Uhm
Show Abstract
The diocotron instability for sheared, relativistic electron flow in a planar diode geometry with major fields Ex(x), Bz(x), and Vv(x) has been studied numerically by using a two-dithensional electromagnetic relativistic particle-in-cell code. The growth rate and real oscillation frequency are obtained and compared to the analytical results for a tenuous electron flow.
Parametric Amplification Using Superconducting Tunnel Junctions.
Author(s):
H. K. Olsson;
T. Claeson
Show Abstract
Stable and low noise operation of a Josephson parametric amplifier has been obtained at 9GHz. Best performance was acheived in the externally pumped modes giving a double side-band noise temperature of 3±4K, a gain of 13B, and an instantaneous bandwidth of 310MHz. An operation mode that uses the internally generated Josephson oscillation as the pump source gave higher noise (-50K) due to the broad width of the pump.
Picosecond Optoelectronics And Millimeter-Wave Technology
Author(s):
Chi H. Lee
Show Abstract
Recent progress on the application of picosecond optoelectronics to microwave and millimeter-wave technology will be reviewed. Generation, control and characterization of pulsed and continuous-wave millimeter-waves will be discussed. A novel network analyzing technique for a 30 GHz monolithic millimeter-wave integrated circuits based on picosecond pulses has been demonstrated.
Experimental Performance Of An Optically Controlled Coplanar Waveguide Phase Shifter With A Thick GaAs Buried Layer.
Author(s):
P. Cheung;
D. P. Neikirk;
T. Itoh
Show Abstract
The experimental performance of an a optically-controlled coplanar waveguide phase-shifter fabricated on a heterojunction substrate containing a thick GaAs layer buried between two A1GaAs layers is presented. The measured performance shows that relative phase-shifts of 1000 can be obtained even for optical input powers in the tW range. Introduction Studies of coplanar waveguides (CPW) on semiconductor multi-layered substrates have shown, that within that the range of resistivities covered by most semiconductor substrates and the frequency spectrum of interest for microwave and millimeter wave applications, a slow wave (SW) mode of propagation can exist [1]. A typical structure consist of a thin lossless layer immediately below the CPW, followed by a thicker lossy layer and a third lossless layer. The slow wave factor (SWF), which is the ratio of the effective guide wavelength to the free space wavelength, is a measure of the change of the effective refractive index of the substrate. The magnitude of the SWF is a function of both the resistivity of the buried lossy layer and the thickness of the first layer. Because of the dependence of the SWF on the properties of the underlying substrate, a CPW on a multi-layered substrate can be used as a variable phase-shifter if either the conductivity or layer thicknesses can be actively controlled. At the 10th IR & MMW conference [2], a method of optically controlling a coplanar-waveguide (CPW) phase-shifter was proposed. By the appropriate selection of semiconductor heterojunction substrate materials (A10.4Ga0.6As / GaAs / Al0AGa0.6As) and the corresponding selection of an illuminating source of the correct wavelength (wavelengths longer than 600 nm, but shorter than 860 nm), the conductivity of the buried GaAs layer can be controlled by the intensity of the optical source. The phase shift is then controlled directly by varying the intensity of the illuminator. At last year's IR & MMW conference [3] preliminary measurements of a prototype device were reported. The results indicated that relative phase shift can be obtained even at relatively low levels of intensity. Recently Kwon, et al [4] showed that the slow-wave mode propagating on the CPW can be modeled by a quasi-TEM circuit model. Using this approach we have developed an equivalent circuit model for an ideal optically controlled CPW phase-shifter [5]. The analysis showed that when a large percent of the total "equivalent thickness" of the substrate is lossy, large relative phase-shifts can be obtained. By conformal mapping this translates into a thick second lossy layer for a typical structure. To test this prediction, a device was fabricated on a substrate with a thick GaAs (711m) layer.
Structural Control Of Microstrip Dispersion For Shaping Giga-Hertz-Bandwidth Pulses
Author(s):
Eikichi Yamashita;
Kazuhiko Atsuki;
Yongxi Qian
Show Abstract
Recent optical switching devices are using combinations of very short laser pulses, photoconductors, and strip lines. Since laser pulses have giga-hertz-bandwidth, signal transmission properties of such strip lines in a wide range of frequencies are decisively important. This paper describes the structural control of the dispersion characteristics of microstrip lines by adding ground conductors on both sides of the strip conductor. Some numerical data are shown.
Inverted Slot Line For Millimeter-Wave Optical Modulator
Author(s):
Tsukasa Yoneyama;
Tomoaki Kato
Show Abstract
The inverted slot line is proposed with the pur-pose of applying to optical modulators operating at millimeter-wavelengths. Velocity of millimeter-waves can be matched to that of optical waves in LiNbO3 material by simply adjusting the spacing between th6 slotted surface and the ground plane.
An Optoelectronic Technique For S-Parameter Measurements Of GaAs Monolithic Integrated Circuits
Author(s):
P. Polak-Dingels;
H.-L. A. Hung;
K. J. Webb;
T. T. Lee;
T. Smith;
C. H. Lee
Show Abstract
An optical technique using picosecond pulses has been developed to characterize the magnitude and phase of the frequency response of a gallium arsenide (GaAs) monolithic integrated circuit in the millimeter-wave frequency range. The results of the complex S-parameters of an amplifier obtained using this technique were compared with those obtained using the network analyzer method.
Effect Of The Light On The Elements Of The Electric Scheme Of A Hemt
Author(s):
D. Pasquet;
B. Zemour;
J. L. Gautier;
P. Pouvil
Show Abstract
An optical fiber has been used to illuminate a HEMT. This causes modifications of the static and dynamic characterics of this component. A home made sophisticated software extracts the elements of the classical electric scheme of microwave FETs from their "S" matrix. The effect of the light on the major elements are decribed and compared with the results for MESFETs.
Josephson Local Oscillator For Integrated Radioastronomical Receivers
Author(s):
R. Monaco;
S. Pagano;
G. Costabile
Show Abstract
We developed a microwave oscillator based on a series array of 100 long Josephson tunnel junctions coherently working in the fluxon resonating mode. This prototype has satisfied all the requirements (output power, frequency, signal stability and purity) for local oscillator in integrated superconducting millimeter receivers.
Balloon-Borne Observations Of The Cygnus Region In The Far Infrared
Author(s):
C. G. Degiacomi;
A. Holenstein;
F. K. Kneubuhl;
D. Huguenin
Show Abstract
A balloon-borne far-infrared telescope has been designed and built to observe the infrared emission from the Cygnus region in the galactic plane between 120 μm and 300 μm wavelength. The system performance, objects as well as results of the first flight in September 1988 will be discussed.
490 GHz Solid State Source With Varactor Quintl1Pler
Author(s):
Ralph Rudiger;
Peter Zimmermann
Show Abstract
This report is about a mechanically tunable solid state source with a varactor quintupler in waveguide technique. Its main purpose was to provide output power at 490 GHz for use in a radioastronomy receiver (1). The device has been tested between 470 and 550GHz. Results are presented as increase in rectified current in a dc-biased Schottky-Detektor.
Induction-Linac Based Free-Electron Laser Amplifiers For Plasma Heating
Author(s):
R. A. Jong
Show Abstract
We describe an induction-linac based free-electron laser amplifier that is presently under construction at the Lawrence Livermore National Laboratory. It is designed to produce up to 2 MW of average power at a frequency of 250 GHz for plasma heating experiments in the Microwave Tokamak Experiment. In addition, we shall describe a FEL amplifier design for plasma heating of advanced tokamak fusion devices. This system is designed to produce average power levels of about 10 MW at frequencies ranging from 280 to 560 GHz.
Current Theoretical And Experimental Issues On Free-Electron Lasers
Author(s):
F. Hartemann;
J. M. Buzzi;
G. Mourier;
G. Faillon
Show Abstract
After a brief review of the basic free-electron laser (FEL) physics, we will discuss the following topics : efficiency optimization of a millimeter-wave FEL, optical guiding experiments in a microwave FEL and pulse shaping and compression in a FEL amplifier.
Mode Competition, Suppression And Control In Fel Oscillators
Author(s):
Baruch Levush;
Thomas M. Antonsen Jr.
Show Abstract
The effect of multimode interaction on the efficiency of a low gain FEL oscillator fed by a continuous beam is investigated. Calculations that enable one to design a device in such a way that it will operate at a single frequency with maximum efficiency will he presented. The model we consider is the one dimensional, low gain oscillator.' Due to low gain, the radiation field in the resonator can he expressed as a superposition of empty cavity modes whose amplitudes and phases change slowly in time (compared with the transit time of the electrons through the interaction region) due to their interaction with the beam. The field at any point will he nearly periodic in time with a period equal to the round trip travel time of radiation in the cavity, which we assume to he much smaller than the time scale over which the amplitudes change. We may then numerically integrate the following set of equations.
Higher Harmonic Emission In The Uniform Magnetic Field Free-Electron Laser
Author(s):
Josip Soln
Show Abstract
With the help of the unitary S matrix in the linear recoil approximation, the study of the spontaneous and the stimulated emission and absorption of higher harmonics in the uniform magnetic field free-electron laser is being pursued. The stimulated emission of single-mode photons, being due to just one harmonic, can be tuned to cover a rather limited frequency range, particularly the far-infrared/microwave spectral region. The spontaneous emission, because it is due to all the harmonics, covers a wide spectral region; consequently, at least in principle, it should be able to stimulate at least some higher harmonic radiation. Here, for theoretical and practical reasons, we limit our study largely to harmonics whose emission (absorption) occurs at angles that are "slightly" different from zero with respect to the uniform magnetic field.
A High Power, 600 THm Wavelength Free Electron Laser
Author(s):
D. A. Kirkpatrick;
G. Bekefi;
A. C. DiRienzo;
H. P. Freund;
A. K. Ganguly
Show Abstract
We report high power emission (18 MW) at a wavelength of λ = 640 μm and a bandwidth ΔAλ/λ< 0.04 from a superradiant free electron laser (FEL) excited by a 2MeV, 1 kA electron beam. Comparison of the experiment with a nonlinear simulation yields good agreement. Theoretical extrapolation to a tapered wiggler experiment shows that power levels of 140 MW could be achieved with an efficiency of 7%.
Betatron-Synchrotron Resonances In Free Electron Laser
Author(s):
Yi-jin Shi
Show Abstract
In terms of Bogoliubov's nonlinear oscillation thoery, the first five betatron-synchrotron resonances of Ω=(p/q)2kβ=1/2,1,3/2,1/3,2/3 which may occur during laser satulation establishing process have been generally examined. Contrast to previous studies it is found that the most dangerous resonance does not take place in the vicinity of Ω=2kβ but in that of Ω=kβ. The width of region of Ω=kβ is proportional to ε with ε∝ (k2w/kβ)*emittance, the passing 'time' over the region due to he laser field being amplified is only one pass over the undulator at most and depends on the gain, and the increment of synchrotron amplitude in passing time is proportional to ε. In summary we conclude that the betatron-synchrotron resonances does not have any significant effect for detrapping off-axis electrons in a practical case.
The Efficiency Improvement Of A Raman Free Electron Laser (FEL)
Author(s):
Zhijiang Wang;
Lifen Zhang;
Zaitong Lu;
Jizhong Chen
Show Abstract
We have developed a first Raman FEL in China [1]. A recent experiment for improving the efficiency is reported. The wiggler length has been enlarged from 79 cm to 119 cm, the efficiency of 3.7% was obtained.
A Prototype Commercial Orbitron Maser For Millimeterwave Radar
Author(s):
M. G. Niimura;
F. Dyer;
M. Rader
Show Abstract
A rugged, compact, battery-powered millimeterwave (mm-wave) radar has been developed by using a prototype orbitron maser as the source. The orbitron maser was found suitable for such an application since it is high power, wideband (thus multi-channel) and frequency tunable. The radiation emanating directly from the tube was fairly uniform and the divergence angle (100) was diffraction-limited. The orbitron pulse had a fast risetime (10Ons), short pulsewidth (500ns) and no spurious oscillations. The orbitron output power was 6.7W minimum (possibly ~6.7kW due to the detector saturation and 400kW input power) at the V-band (50-75GHz). The power levels were similar at lower bands and constant up to 10Hz of repetition frequency. An innovative DC-DC converter was used to amplify 24V of battery potential up to 1000 times. The orbitron maser was characterized by simultaneous measurements of the applied voltage, discharge current (thus input-power and plasma-resistance), luminousity and wave signal. A linear scaling law was found for the mm-wave power to increase with the discharge current. Output power with hydrogen was twice to that observed with air or nitrogen working gases.
A Low-Loss High-Power Filter For Direct Broadcast Satellite Transponders
Author(s):
Toshihiro Nomoto
Show Abstract
In designing broadcast satellite transponders, it is required for the filters handling high-power RF signals to have not only low-loss characteristics but also good thermal stability. In order to realize such filter performance, we proposed a 6-pole canonical TE113 dual-mode filter which is formed of silver-plated Super Invar cavities with copper iris plates. The insertion loss and thermal stability of the experimental filter were 0.3dB and 1.5ppm/C, respectively. Also, no significant deteriora-tion on the filter performance was observed even at the RF input power of around 400W. AS a result, it was found that this type of filter was most suitable for the high-power satellite transponders in view of insertion loss, thermal design, volume and weight.
A Model Based Technique For Millimeter Wave Radar Target Recognition
Author(s):
Firooz A. Sadjadi
Show Abstract
A technique for recognizing real targets by millimeter wave (MMW) radar at 35 GHz and 94 GHz is presented. The recognition is performed by a model based technique in which real targets are represented by their high range resolution (HRR) profiles in a hierarchical fashion. The unknown signal is classified by a model matching method and a coarse-fine searching technique. The advantages of this model based method are in low storage capacity, fast processing time and high recognition performance. Moreover this technique is very easily modifiable to incorporate infrared sensor processing. We will present the results of the several experiments that we have conducted.
Recent Advances In Millimeter Wave Up And Down Converters
Author(s):
Charles Oleson;
Arthur Larsen;
Richard Chew;
Walter Day
Show Abstract
A 26 to 40 GHz block converter for receiver frequency extension will be described. The converter has a 15 dB NF, 10 dB, conversion gain, ≥.5,0 d spurious-free dynamic range, built in BITE, 44 GHz L.O. and measures 3x3x1 inches. A 33 to 36 GHz up/down converter for an airborne jammer pod will also be described.
205 GHz Sis Receiver Development For Remote Sensing Applications
Author(s):
W. R. McGrath;
C. N. Byrom;
B. N. Ellison;
M A. Frerking;
R. E. Miller
Show Abstract
There are many applications of remote sensing in the frequency range near 200 GHz. The determination of the role of man-made chlorine compounds in the destruction of the ozone layer observed through the emission from C/O near 200 GHz is one example. Another example is the observation of CO at 230 GHz as a tracer of matter in the interstellar medium. Heterodyne receivers are the instrument of choice to perform these observations due to their high sensitivity and spectral resolving power. The nonlinear tunneling currents in a superconductor-insulator-superconductor (SIS) tunnel junction have been shown both theoretically and experimentally[1] to provide the lowest noise mixing element at millimeter wavelengths in these receivers. When properly optimized, an SIS mixer displays the important properties of conversion efficiency greater than unity and noise temperature approaching the quantum limit.
Light-Controlled Microstrip Line Coupler
Author(s):
Hitoshi Shimasaki;
Makoto Tsutsumi
Show Abstract
An optically-controlled microstrip line coupler is analysed based on Galerkin's method in the spectral domain. The scattering parameters of ports are derived as a function of plasma density in semiconductor substrate. Results are confirmed by experiments in the frequency band from 1 to 15 GHz.
Optical Generation And Distribution Of Microwave Signals
Author(s):
George J. Simonis;
Kenneth G. Purchase
Show Abstract
We report the results of the optical generation of microwave signals superimposed as a modulation on an optical carrier by means of laser heterodyning. The modulated optical carrier can be easily distributed with fiber-optic cables. This approach offers microwave distribution advantages in size, weight, cost, and frequency diversity, which are desirable in improtant applications such as phased antenna control.
A CO2 Laser Thomson Scattering Diagnostic For The Measurement Of Fusion Product Alpha Particles
Author(s):
R. K. Richards;
C. A. Bennett;
L. K. Fletcher;
H. T. Hunter;
D. P. Hutchinson
Show Abstract
A Thomson scattering diagnostic for measuring the alpha particle velocity distribution is described. Calculations of scattering are made for a CIT type plasma using available CO2 laser and heterodyne technology. Tests of a long pulse CO2 laser, multichannel heterodyne detector, and an absorption cell for stray laser radiation are presented.
Ecrh Of Trapped Electrons In Tokamaks
Author(s):
S. P. Kuo;
M. C. Lee
Show Abstract
Heating of plasma electrons by high power millimeter wave fields at the electron cyclotron harmonic resonance is studied. A mirror magnetic field is modelled for investigating the local trapping of electrons. Then, the suprathermal electrons generated by the ECRH of trapped electrons is analyzed. It is generally believed that these hot electrons can be used to produce the average minimum B field configuration for stabilizing the interchange mode.
Megawatt Cw Millimeter Wave Transmission Systems
Author(s):
M. Thumm;
H. J. Barkley;
W. Kasparek;
G. A. Muller;
P. G. Schuller
Show Abstract
The properties of highly oversized tubular HE11 waveguide (circumferentially corrugated or dielectrically lined metal guide) and of quasi-optical Gaussian beam waveguide (using focusing metallic mirrors) are reviewed and compared in order to extract the specific advantages and disadvantages of these two approaches for use in low-loss megawatt CW millimeter-wave transmission systems. Manufacturing imperfections may limit the application of the convenient HE11 waveguide to the 1 MW / 100 to 140 GHz range. Quasi-optical transmission is ideal for multi-megawatt millimeter- and submillimeter-wave systems using beam combination. Depending on the power and frequency requirements and on the accessibility constrains, combined systems may be realized.
Low Loss Broadband Multimode Circular Corrugated Waveguide Performance
Author(s):
A. Cavallo;
J. Doane;
R. Cutler;
J. Brenner
Show Abstract
A 30 meter long circular corrugated waveguide run (i.d.=6.35 cm) with a corrugation period and depth of 250μ has been fabricated. It is designed for low loss (<0.01 dB/m) multimode operation over the frequency range of 75-575 GHz. It will be installed on TFTR (Tokamak Fusion Test Reactor) for use in electron cyclotron emission measurements. Results will be compared to those obtained using conventional tall rectangular C-band waveguide.
Initial Operation Of A Polarization-Controlled Beamed Ech Launcher
Author(s):
T. S. Bigelow;
C. R. Schaich;
T. L. White
Show Abstract
A system for launching 53.2-GHz electron cyclotron heating (ECH) power is being installed on the Advanced Toroidal Facility (ATF) fusion experiment at Oak Ridge National Laboratory. The launcher provides a narrow linearly polarized beam. The plane of polarization is easily rotated. Measurements indicate that the launcher will have a -20 dB beam width of 15 cm at the plasma center and polarization purity of >97%. The ATF (1) requires 53.2-GHz microwave power for ECH plasma ionization and heating; this power is generated by a 200-kW cw gyrotron. Theoretical ray tracing studies have shown almost complete first-pass power absorption is possible if the power is within the saddle point in the proper polarization (2). Therefore, a narrow-beam-width launcher with adjustable polarization is being developed. In ATF the confining magnetic field can operate continuously at 1 T or in long pulses at 2 T. Either second harmonic or fundamental ECH absorption occurs, depending on the field strength, and it is of interest to operate experiments using both values. With perpendicular propagation and low-field-side launch, the ECH power must be in the extraordinary mode (X-mode, Erf perpendicular to Bo) for second harmonic (co = 2 wee) or in the ordinary mode (0-mode, Enr parallel to Bo) for fundamental (o) = c),) operation. The magnetic field in ATF is formed primarily by helical windings, which produce a shear in the plane of the field along a radial chord. This shear may cause polarization rotation of the ECH wave as it travels through the outer plasma regions because of the unequal 0- and X-mode phase velocities at higher plasma density (similar to Faraday rotation). The ECH resonance zone is a 10-cm-wide saddle point near the plasma center.
Very Short Quasi-Periodic And Aperiodic Mode Converters For 60 And 140 GHz Gyrotron!
Author(s):
M. J. Buckley;
G. H. Luo;
R. J. Vernon
Show Abstract
Very short, broad bandwidth designs will be discussed for varying-radius mode transducers for TE02-TE01 and TE03-TE02 mode conversion in a 2.779 cm diameter circular waveguide at 60 and 140 GHz and for TE15, 2-TE15, 1 mode conversion in 2.54 cm diameter waveguide at 14'0 GHz.
An X-Band Vlasov-Type Mode Convertor
Author(s):
B. G. Ruth;
C. D. Schlesiger;
R. K. Dahlstrom
Show Abstract
The far-field radiation patterns from three different circular waveguide antennas are measured with an antenna pattern-mapping system. The radiating ends of the waveguide antennas are each cut at a specific angle relative to the center axis of the waveguide, forming the waveguide launcher component of a Vlasov-type mode convertor. This paper addresses the radiation patterns launched from the waveguide antennas as the first step in the design of a Vlasov-type mode convertor that will function at high power levels in the X-band frequency range (8 to 12 GHz).
Design Of The Cit Gyrotron Ecrh Transmission System
Author(s):
J. A. Casey;
P. Woskov;
D. Cohn;
R. Temkin
Show Abstract
Plans for Electron Cyclotron Resonant Heating in the Compact Ignition Tokamak call for at least 10 MW at fields from 7T to 10T with extension to 40 MW possible. 1 MW CW Gyrotron sources for fundamental heating are currently in the design phase. The transmission system must accomodate these high powers in addition to the constraints of small space and access in a tritium environment. Quasi-optical and corrugated guide systems are under consideration, as well as hybrid designs. A preliminary design is presented, and options for alternatives are discussed.
Preliminary Low-Power Investigation Of Teon Mode Vlasov Launchers
Author(s):
P. J. Sealy;
R. J. Vernon
Show Abstract
Preliminary results for an experimental and theoretical investigation of TEON mode Vlasov launchers which might be used in conjunction with some gyrotrons will be discussed. We will present experimental radiation patterns taken directly from the half-cylinder baffle and also from the parabolic-cylinder reflector that it feeds. Variations of the half-cylinder baffle and orientation position of the parabolic reflector will be considered.
Observation Of Ubitron Fundamental Mode Amplification
Author(s):
Robert H. Jackson;
Dean E. Pershing;
Hans Bluem
Show Abstract
Operation of a ubitron/FEL amplifier is reported. The experiment has been operated using the fundamental wiggler harmonic interaction with the TE11 circular waveguide mode. Small signal gains as high as 12dB have been observed at a voltage 15% below design level with a minimum instantaneous bandwidth exceeding 25%. A gain per free-space wavelength approaching 0.9dB/λ has been achieved. Experimental results are compared with small signal calculations and future plans are discussed.
Optimization Of A Planar Orotron
Author(s):
J. E. Walsh;
J. A. Jackson;
E. M. Marshall
Show Abstract
The Planar Orotron has traditionally consisted of a uniform, rectangular metal grating opposed by a planar conductor (Fig. la)Unbounded at the sides, this open resonator supports travelling waves with frequencies which are determined by the grating dimensions. The dispersion and gain characteristics for this device have been documented theoretically and experimentally in the low beam voltage (5 - 20 kV) regime,1 where powers of up to 2 kW and efficiencies of a few percent at 35 GHz have been recorded. In the frequency range of 150 to 175 GHz , output powers are typically less than 1 W, and efficiencies less than 0.5%. Attempts to improve the output power and efficiency by modifying the resonator design are currently underway in the 30-40 GHz range. Among the new designs are the following, which appear in Figures 1 and 2: 1) A uniform grating is opposed by an identical uniform grating, with a symmetric orientation in the resonator. (Fig. lb) 2) A uniform grating is opposed by an identical uniform grating, with an antisymmetric orientation in the resonator. (Fig. lc) 3) The uniform grating is replaced by a grating with a slight taper (< 10%) and opposed by a conducting plane. (Fig. 2a) 4) The tapered grating is opposed by an identical tapered grating with a symmetric orientation in the resonator. (Fig. 2b) The grating and resonator parameters of interest are shown in the Figures. They are the period, l, and the ratios of groove depth to grating period, d/1 , groove width to grating period, s/l , and the ratio of inner resonator height to grating period, (b-d)/l. In Fig. 2, the groove depth, d, and the distance from the base of the slot to the surface of the opposing component, b, are both functions of the axial position, z.
The Circular Orbit Linear Theory Of Axial Injection Orbitron Maser Oscillators
Author(s):
John M. Burke
Show Abstract
A fully relativistic theory of axial injection orbitron maser (AXIOM) oscillators has been completed. The theory models the interaction of axially injected electrons in helical trajectories with the fields of a coaxial cavity resonator. The theory treats TE or TM modes with sinusoidal axial field profiles. The power transferred from the electron beam to the cavity fields is calculated in terms of a general distribution function and the cavity parameters. A cold beam distribution function is used to evaluate the theory. The results of the theory are presented in terms of the threshold value of the cavity Q times the electron beam current IBeam required for self-oscillation.
Pulsed And Steady-State Multinode Orbitron Masers
Author(s):
I. Alexeff;
F. Dyer;
M. Rader
Show Abstract
We have designed, built and tested several steady-state Orbitron MASERs, which have the unique property of having multiple anode wires. We have found that the multiwire structure increased the output power, efficiency, and reduced the heat loading of individual anode wires. We have also experimented with these devices in a pulsed mode and found similar results.
High Efficiency Operation Of The Modified Peniotron Riqtma Tr Twptammilar Wwproltnp Ranittv
Author(s):
K. Yokoo;
M. Razeghi;
N. Sato;
S. Ono
Show Abstract
The modified peniotron oscillator proposed by the authors has been experimentally studied and a fairly high electronic efficiency 50% and 62% of the efficiency by the use of a potential-depressed collector were obtained. This paper describes the operation characteristics of the modified peniotron and point out that the alignment of the respective axes of the tube and the magnetic circuits is very important in a peniotron tube.
Auto-Resonant Peniotron For High Power Millimetre Wave Generation With An Extremely High Efficiency
Author(s):
K. Yokoo;
S. Ono;
N. Sato
Show Abstract
We propose a new configuration of the auto-resonant peniotron oscillator(ARPO) consisting of an oscillator part with a low output power and an amplifier part and report the analytical results of its operational characteristics. The results show that a multi megawatts oscillator tube with an extremely high conversion efficiency should be possible to develop even in the millimetre and the submillimetre wave regions.
A New Fundamentally Pumped Balanced Mixer For G-Band (140-220 GHz )
Author(s):
I. Galin
Show Abstract
This paper presents a structure for a fundamentally pumped balanced mixer with whisker contacted diodes. The structure suggests compact and unique solutions for placing two connected diodes in an extremely small hybrid T, and for a low loss adjusted waveguide short. At 183 GHz this mixer's noise temperature was under 600 K double-sideband measured at room temperature, a figure achieved until now only with single-ended mixers.
Large-Area Bolometers For Millimeter-Wave Power Calibration
Author(s):
Gabriel M. Rebeiz;
Curtis C. Ling;
David B. Rutledge
Show Abstract
An accurate monolithic power meter has been developed for millimeter-wave applications. The detector is a large-area Bismuth bolometer, integrated on a fused-Quartz substrate. It simply measures the temperature change caused by the absorption of millimeter-wave radiation. The power meter is easy to fabricate, and can be calibrated using a low-frequency network. The measured responsivity for a 1x1cm bolometer is about 1mV/W, at a bias of 1V. and a video modulation of 100Hz. The noise spectrum exhibits a 1/f rolloff below 1KHz, and is limited by the Johnson noise for higher frequencies. The NEP of the detector is 3x10-6W H z -1/2 at a video modulation of 1 KHz. It is possible to decrease the current NEP by fabricating bolometers with higher responsivities. Possible application areas are absolute power calibration and localized power-density measurements for millimeter and submillimeter wavelengths.
Series-Connected Josephson-Effect Mixers For Millimeter-Wave Radiation
Author(s):
Hiroshi Ohta;
Toshiaki Matsui;
Bokuji Komiyama
Show Abstract
Millimeterwave detectors have been made of a series-connected array of Josephson junctions. Each junction of the array responds in phase to radiation and therefore the series-connected array as a whole behaves as if it were a single Josephson junction. When the Josephson junctions have a high critical current density, the IF outputs have sharp peaks at the voltages V = 2NΔ/ne where N is the number of the Josephson junctions in series connection and n is an integer. The subharmonic energy gap structures in voltage-current curves of Josephson junctions come from the Andreev-reflection-assisted-tunneling according to the recent Arnold theories.
A Multichannel Submillimeter Wave Interferometer System On Atf
Author(s):
D. P. Hutchinson;
C. H. Ma;
K. L. Vander Sluis;
C. A. Bennett;
J. Lee
Show Abstract
A high resolution multichannel far-infrared interferometer has been constructed for the ATF experiment at Oak Ridge. The system consists of a pair of cw 119-pm methanol lasers, optically pumped by separate CO2 lasers. An external Stark-cell modulation scheme is used to stabilize the frequencies of the CO2 lasers. The system is designed to be operated, monitored, and stabilized by a PC computer.
Fir Polarimeter/Interferometer For Jipp T-II U
Author(s):
A. Yasuda;
K. Kawahata;
J. Fujita;
S. Okajima;
Y. Nagayama
Show Abstract
A one channel FIR polarimeter/interferometer, with HCN laser of 0.337 mm is designed for JIPP T-II U Tokamak, in order to prove the possibility of the inference of current density distribution. The measurement itself is successful, of the distributions of the line density and Faraday rotation angle with the accuracy of 0.1 fringe and 0.1 degree respectively.
A Multichannel Hcn Laser Interferometer For Electron Density Measurements On The Jipp T-Iiu Tokamak
Author(s):
K. Kawahata;
J. Fujita;
A. Yasuda;
S. Okajima
Show Abstract
A six-channel HCN laser interferometer system has been developed for the measurement of the electron density profile in the JIPP T-IIU tokamak. The optical configuration is of the Michelson interferometer type, of which reflecting mirrors are directly attached on the wall of the vacuum vessel. This optical configuration enables the density profile measurements by the multichannel laser interferometer with a small optical window.
Scattering Of Millimeter-Submillimeter Radiation From The Tortus Tokamak Plasma
Author(s):
M. D. Bowden;
P. W. Fekete;
M. J. Ballico;
G. F . Brand;
I. S. Falconer;
B. W. James;
K. J. Moore;
T. Idehara
Show Abstract
A formic acid laser operating at 433 μm and a gyrotron which is step-tunable in the range 75-330 GHz are being used to study density fluctuations in a small tokamak during Alfven wave heating. The scattering systems and recent results will be discussed.
A High Power Ch3Oh Laser System Using Stark Stabilized CO2 Pump Lasers'
Author(s):
D. P. Hutchinson;
C. A. Bennett;
J. Lee;
L. K. Fl etcher;
C. H. Ma;
K. L. Vander Sluis
Show Abstract
A dual channel, 119μm wavelength laser system has been constructed for the ATF experiment at Oak Ridge. The pump lasers utilize external Stark cells for locking the CO2 laser to the absorption frequency of the CH3OH lasers. Stark plates have also been attached to the dielectric waveguide resonators of the FIR lasers to affect precise tuning of the 119 μm lasers.
Simultaneous Multiline Operation Of A Formic Acid Laser And Applications
Author(s):
M. D . Bowden;
I. S. Falconer;
B. W. James;
L. B . Whitbourn;
J C. Macfarlane
Show Abstract
A formic acid laser has been operated simultaneously on three lines of a cascade sequence by suitable choice of the resonator length, resulting in enhanced power on all three lines. The phenomenon can be used to construct a phase-modulated interferometer. For the output coupler used which exhibits phase anisotropy, simultaneous output on two orthogonally polarized lines of a cascade sequence has also been obtained.
Ion Temperature Measurements In A Tokamak By Collective Thomson Scattering Of Fir Laser Radiation
Author(s):
R. Behn;
D. Dicken;
J. Hackmann;
S. A. Salito;
M. R. Siegrist
Show Abstract
As a result of steady progress in high power FIR lasers and sensitive, low-noise detection systems, the equipment is now available to measure the ion temperature (Ti) of tokamak plasmas by Thomson scattering from thermal density fluctuations. Using a laser in the far-infrared wavelength range permits scattering angles as large as 90° which results in excellent spatial resolution of the measurement. Heterodyne receivers built around Schottky barrier diode mixers combine high sensitivity with large electrical bandwidth to cover the frequency spread of the scattered radiation. After a first demonstration of feasibility was reported by Woskoboinikow et al (1), recent improvements on our system made it possible for the first time to measure Ti in a single laser shot.
Design And Calibration Of A Two-Channel Low Noise Heterodyne Receiver At 10.6 Microns
Author(s):
C. A. Bennett;
R. K. Richards;
D. P. Hutchinson
Show Abstract
A dual channel, low noise heterodyne receiver has been constructed for Thomson scattering from alpha particles in a burning plasma experiment. A real time calibration method has been devised which references the integrated system noise to a blackbody source. Two wideband (>1GHz) HgCdTe photovoltaic mixers yield a double sideband system noise equivalent power of less than 1.5 x 10-20 W/Hz.
Calibration Of 10-Channel Grating Polychromator
Author(s):
K. Kawahata;
M. Sakamoto;
J. Fujita;
H. Matsuo;
K. Sakai
Show Abstract
A high temperature (T = 500°C) radiation source has been developed for the calibration of electron cyclotron emission measuring system on the JIPP T-IIU tokamak. The source has a heated area of (1)150 mm, and has the same emissivity as that of the microwave absorber Eccosorbe. The grating polychromator has been calibrated using the radiation source developed. The obtained electron temperatures agree with those by Thomson scattering within 10%.
A Stark-Tuned Ch Ohlaser For Use In High Frequency Modulated Interferometry
Author(s):
D. K. Mansfield;
M. Vocaturo;
L. Guttadora
Show Abstract
A Stark-tuned laser operating on the 119 micron line of CH3OH has delivered reasonably high power (several tens of milliwatts at 30 Watts of pump power) while simultaneously exhibiting a doublet splitting of about 10 MHz, which is an order of magnitude larger than the modulation frequencies currently being used in plasma interferometers. Because the resonator design has allowed the attainment of both high power and high doublet splitting, this type of laser would be usable in the type of multi-channel interferometers currently employed on the large-scale plasma devices being used in magnetic fusion research.
The Effects Of Turbulence In Clear And Turbid Atmospheres On Millimeter Wave Propagation
Author(s):
R. W. McMillan;
R. A. Bohlander;
R. J. Hill;
S. F. Clifford
Show Abstract
Atmospheric turbulence, which is a readily observed phenomenon at visible wavelengths, also causes fluctuations in intensity and phase at millimeter wavelengths. This paper describes a series of experiments conducted at a site near Flatville, IL which measured these effects at a broad range of MMW frequencies in clear air, rain, fog, and snow. It was found that the maximum rms intensity fluctuations observed were 14% of the mean, while the largest rms angle-of-arrival fluctuations were 36 microradians. Discussions of the experimental arrangement, as well as results obtained in measuring the probability distribution functions of fluctuations, the mutual coherence function, spectral densities, and pertinent atmospheric parameters will be presented.
Atmospheric Attenuation And Delay Rates Between 1 GHz And 1 THz
Author(s):
Hans J. Liebe
Show Abstract
A practical, PC-operated atmospheric propagation model (MPM) was developed by ITS that predicts attenuation (dB/km) and delay (ps/km) rates for frequencies between 1 GHz and 1 THz. Input variables are barometric pressure, ambient temperature, relative humidity, hygroscopic aerosol concentration, suspended water or ice droplet concentration, and rain rate. Details of the MPM code are discussed briefly, model predictions are presented, and comparisons with data from propagation experiments studying water vapor and fog effects (50 to 430 GHz) are shown.
An Algorithm For Estimating Cloud Attenuation At Millimeter Wavelengths
Author(s):
Edward E. Altshuler;
Richard A. Marr
Show Abstract
Total atmospheric attenuation under conditions of cloud cover was measured at frequencies of 15 and 35 GHz using the sun as a source. Over 300 sets of data were collected at each frequency. An algorithm for estimating the slant path attenuation under conditions of cloud cover as a function of elevation angle, frequency and surface absolute humidity was derived.
Millimeter Wave Atmospheric Propagation Study At Crl
Author(s):
T. Ihara;
T. Manabe;
J. Awaka;
Y. Furuhama
Show Abstract
Communications Research' Laboratory conducted millimeter wave propagation experiemnts at radio window frequencies 1.7, 11.5, 34.5, 50.4, 81.8, 140.7, 245.5 GHz and at 350 THz on shrot terrestrial paths in a suburb of Tokyo during 1979 - 1986. Main results of these experiments will be presented.
Mesospheric Radiowave Propagation In The 60 GHz Band Affected By Zeeman-Split Oxygen Lines
Author(s):
H. J. Liebe;
G. A. Hufford;
A. S. Katz
Show Abstract
A model was developed to analyze anisotropic propagation of plane, polarized radiowaves in the mesosphere as influenced by the geomagnetic Zeeman effect displayed by 02 spectral lines positioned in the 60 GHz band. To provide an example here, the 5+ line, centered at the frequency fo = 59.59058 GHz, has been chosen and two cases are discussed: from a location known by latitude and longitude, a radiowave (a) propagates north in an altitude of 75 km at the frequency fo + 1 MHz covering a distance of up to 1000 km; and (b) enters the atmosphere at 100 km altitude, heads in either N, E, S, or W directions, descends to the 75 km level, and then exits again. In the first case, attenuation and polarization state are followed along the path; in the second case, total path attenuations as a function of frequency deviation (f0±MHz), initial polarization, and direction are given.
Status And Future Plans Of High Power Sources For Plasma Heating
Author(s):
T. V. George
Show Abstract
The presentation will address the motivation, the strategy and the plan for developing high average power millimeter wave sources under the sponsorship of the Office of Fusion Energy, Department of Energy. Ongoing efforts and expected trends in line with the recent recommendations of a number of review panels will be discussed. The presentation will also highlight some of the fusion experimental applications.
Megawatt Gyrotrons For ECR Heating
Author(s):
K. FeIch;
C. Hess;
H. Huey;
E. Jongewaard;
H. Jory;
R. Pendleton
Show Abstract
Varian is in the process of developing gyrotrons capable of generating power levels of 1 MW CW at a frequency of 140 GHz. The first experimental gyrotron in this program has been designed to generate short-pulse power levels of 1 MW and up to 400 kW CW. In recent tests on this gyrotron, a short-pulse power level of 820 kW was obtained at 21% efficiency. While operating at peak power levels of 350-400 kW, the duty factor was raised to 10% (30 pps, 3.33 ms-pulse duration). Power losses in various parts of the tube have been measured and are in agreement with theoretical predictions. Tests at higher average powers, up to the 400 kW CW goal for the tube, are underway. Design efforts aimed at increasing the average power capabilities of the gyrotron up to 1 MW are in progress.
Experimental Studies On The 120 GHz Gyrotron Of Mitsubishi Electric Corp.
Author(s):
T. Kikunaga;
T. Shimozuma;
H. Asano;
Y. Yasojima;
Y. Murai;
K. Nakashima;
T. Tsukamoto
Show Abstract
Design and experimental studies of the 120 GHz, TE03 mode gyrotron of Mitsubishi Electric Corp. are reported. Since the first operation of our 120 GHz, TE03 mode gyrotron (1), our efforts have been aimed at increasing an output power on the second tube. The second tube is a modular type and allows interchange of important parts such as a magnetron injection gun, a cavity and a window. The tube with a nonlaminor gun and a simple tapered cavity (Q=579) has achieved the maximum output power of 167 kW at 120 GHz in the TE03 mode with short pulse. The efforts for increasing pulse width have been also continued. A 150 kW, 10 msec, sealed type of gyrotron was reported at the 5th Annual Conference of the Japan Society of Plasma Science and Nuclear Fusion Research (March, 1988). In this paper, most part is devoted to descriptions of short pulse operation on the second tube. The rest introduces the design of a complex cavity for high power (~200kW) and long pulse (~100ms) gyrotrons.
The Design Of Megawatt Gyrotrons For The Compact Ignition Tokamak
Author(s):
K. E. Kreischer;
T. L. Grimm;
A. W. Mobius;
R. J. Temkin
Show Abstract
A 1 MW, 280 GHz gyrotron oscillator suitable for ECR heating of the Compact Ignition Tokamak (CIT) is presently being designed. The design is based on successful features of our present experiment, which has generated powers up to 765 kW in the TE16,2,1 mode at 148 GHz. In the 280 GHz gyrotron, an 80 kV, 50 A annular beam will interact with a high order whispering gallery mode. Parametric studies indicate that a cavity with a diameter of at least 20A is required to keep wall losses low. Detailed studies of the electron gun and 12 T magnet indicate both are feasible. Initial experiments are planned for late next year.
Depressed Collectors For Gyrotrons
Author(s):
M. E. Read;
A. J. Dudas;
W. Lawson;
A. Singh
Show Abstract
The gyroklystron is a potential source for driving advanced accelerators, such as the proposed 300-500 GeV electron-positron collider. Sources with frequencies higher than those commonly used in accelerators (e.g. 2.9 GHz) are desired because higher accelerating gradients can be created, thus reducing the length and cost of the device. Because of the inherent advantages of gyrotrons, such a source is expected to be able to produce significantly higher power at high frequencies than that possible with a linear beam tube. A 10 GHz, 30 MW gyroklystron is being developed at the University of Maryland to demonstrate this potential.[1]
Gyrotron IV- A New Tunable Gyrotron
Author(s):
G. F. Brand
Show Abstract
GYROTRON IV is the latest in a series of tunable gyrotrons designed and constructed at the University of Sydney (1). Like GYROTRON III, it is tuned by raising the field of a 12 T superconducting magnet. One cavity resonance after another is excited. It will provide more than 10 W of cw power over the frequency range 75 to 330 GHz. However, a number of design changes have been made to simplify the construction and improve the quality of the output.
Characteristics Of Coupled Planar Strip-Slot Resonators With Multiple-Layer Dielectrics
Author(s):
Aosheng Rong;
Sifan Li
Show Abstract
Coupled planar strip-slot resonators with multiple-layer dielectrics are investigated by the reaction theorem in electromagnetic field theory. A variational formula for the resonant frequency is established, which involves only the electric fields on slots and the electric currents on strips. Two coupled suspended rectangular strip-slot resonators are computed. The numerical results agree well with the experimental data.
Excitation And Transmission Measurements Of Dielectric Rod Waveguide He 11 Mode In The 50-150 GHz Range
Author(s):
Y. Yamamoto;
K. Fujisawa
Show Abstract
The sole excitation of the HE11 mode along the dielectric rod waveguide up to the 150 GHz band has been studied. Measurements have been done on the guide-wavelengths along the TPX rod waveguide with diameters 3.1, 2.0, 1.5 and 1.0 mm in the 150 GHz band. It has been shown that the TPX rod waveguide with a diameter less than or equal to 1.5 mm can transmit only the HE11 mode in the 150 GHz band.
A New Approach For The Analysis Of Waveguides With Multiply Connected Cross Section
Author(s):
A. S. Omar;
K. Schunemann
Show Abstract
An approach for the analysis of waveguides with multiply connected cross section is presented. It is based on a field expansion with respect to the normal modes of the corresponding hollow waveguide with the same outer conductor. This is in particular useful if the outer conductor has a rectangular or circular cross section. The method can be applied to a large number of guiding structures with both touching and non touching inner conductors. This includes e.g. ridged waveguides, finned waveguides, strip lines, and two wire transmission lines. Here the validity of the method is checked by analyzing a coaxial line.
Modal Analysis Of A Circular Waveguide Bifurcation For CCTWTS
Author(s):
Fujiang Lin;
A. S. Omar
Show Abstract
Using modal analysis, an analytical solution to a circular waveguide discontinuity is obtained which is found in a wide class of coupled cavity travelling wave tubes (CCTWTs). The generalized scattering matrix (GSM) of the junction is obtained for both azimuthally dependent and independent excitations. The convergence of the numerical results is investigated by com-paring the field distributions at both sides of the junction. The (GSM) of the different junctions can be cascaded in order to characterize a single cavity of the TWT structure.
Analysis Of Eccentric Annular Waveguides
Author(s):
Yunsheng Xu;
A. S. Omar
Show Abstract
Cutoff frequencies and field configurations are calculated for both TE and TM modes of the eccentric annular waveguide. In the analysis the cross section of the waveguide is transformed into a coaxial line by conformal mapping. Then TE and TM modes are expanded in terms of the corresponding coaxial modes. Excellent agreement with results obtained by other published methods is achieved. The advantage of the proposed method is its fast convergence.
Characteristics Of Double-Groove Guide For 100 GHz Operation
Author(s):
Yat Man Choi
Show Abstract
There are two types of possible transmission modes in double-groove guides: 1. modes with a concentration of energy in the groove regions, and 2. modes with a concentration of energy in the region between the two grooves. Attention had been concentrated on the first type of modes [1]. This paper gives the theoretical and experimental work on the second type of modes.
Processing And Electrical Properties Of High-Tc Superconductors
Author(s):
R. B. Poeppel;
M. T. Lanagan;
J. P. Singh;
K. C. Goretta;
J. T. Dusek;
S. E. Dorris;
U. Balachandran;
C. L. Bohn;
J. R. Delayen
Show Abstract
This paper presents an overview of ceramic fabrication techniques and electrical properties of high-Tc superconductors. Fabrication of bulk ceramic and composite, high-Tc superconducting wires and tapes is discussed. Direct-current critical current density data and surface resis-tance data at rf and microwave frequencies are presented for the YBa2Cu307-x and Ba2Sr2CaCu208+y phases.
An Open Resonator For Testing Surface Resistivity Of , Superconductor Films & Metallic Samples At 100-120 GHz
Author(s):
T. Matsui;
M. Kiyokawa;
B. Komiyama
Show Abstract
A 100-120 GHz open resonator, which has a hemispherical configuration with a plane mirror as the sample itself, is described as a powerful tool for testing mirror samples. Very, weak coupling, which is necessary for the high Q factor, have been achieved without facing with large transmission loss by using a partially-transparent circular aperture which is larger than wavelength. Weak effect on sample surface is sensitively detected by the precise measurement of high quality factor and frequency shift of the open resonator.
Antiferromagnetic Order In High Tc Superconductor Oxides
Author(s):
S. Yoshimori;
M. Kawamura
Show Abstract
We propose the multi-Cu-02-layer structure model of high Tc superconducting oxides such as Bi2Sr2Ca2Cu3012. The 'hole-Cooper pair' formation and the Bose condensation of the pairs are described by the theory of Huang of MIT. The attractive interaction is due to the antiferromagnetic order of Cu-02 layer. Dependence of Tc on the number of Cu-02 layers is quantitatively analized. Pressure dependence of Tc is also analyzed by use of our model.
Measurement Of Superconductor Surface Impedance By Using A Parallel Plates Open Resonator Excited By Dielectric Rod He11 Mode
Author(s):
K. Fujisawa;
Y. Yamamoto;
F. Okuda
Show Abstract
The principle and experimental setup to measure the superconductor surface impedance is described, which characterizes in using an open resonator. The open resonator comprises a couple of parallel conducting plates penetrated perpendicularly by a thin dielectric rod. Along the dielectric rod, the HE11 mode is excited and its resonance between the parallel plates is exploited for finding the surface impedance of the superconducting plate.
High Dynamic Range Infrared Detectors
Author(s):
A. G.U. Perera;
D. D. Coon
Show Abstract
We describe the use of cryogenically cooled, extrinsic silicon p+-n-n+ diodes in an unconventional mode of operation as infrared detectors[1], which offer an unusually large dynamic range. The use of these detectors for high dynamic range IR radiometry and IR imaging would require no preamplifiers and could open the way to new means of 3-D processing at or near the focal plane. [2] The detectors perform intensity-to-frequency conversion via circuits with very low power consumption. To our knowledge, these are the only detectors which perform direct IR intensity-to-frequency conversion in the detector itself.
Pyroelectric Infrared Detectors For Precision Earth Sensor
Author(s):
K. Nakamura;
T. lshigaki;
A. Kaneko;
S. Takahashi;
J. Nishida;
Y. Wakabayashi;
H. Nakamura
Show Abstract
New IR detectors with twin elements were developed for precision earth sensors of satellites. Two sorts of pyroelectric elements, ceramics and sputtered films, were studied. Each element is mounted on an immersion lens. Minimum random error of attitude measurement is much smaller ( 0.012°) than that ( 0.06°) of our preceding type.
The Dependence Of Gaas Schottky Diode Noise On Dry Etching Damage
Author(s):
T. Suzuki;
T. Iinuma;
K. Mizuno
Show Abstract
The noise of GaAs Schottky diode caused by dry etching damage has been studied. The number of traps near the Pt/GaAs interface increases with the damage, and this greatly increases flicker noise. These experimental results can be explained by a theoretical calculation.
Adiabatic Demagnetization Cooler For Far Infrared Detector
Author(s):
Akio Sato;
Takashi Yazawa;
Junya Yamamoto
Show Abstract
An small adiabatic demagnetization cooler for an astronomical far infrared detector has been built. Single crystals of manganese ammonium sulphate and chromium potassium alum, were prepared as magnetic substances. The superconducting magnet was indirectly cooled and operated by small current up to 13.3 A, the maximum field being 3.5 T. As a preliminary step, adiabatic demagnetization to zero field was implemented. The lowest temperature obtained was 0.5 K, for 5.0 K initial temperature.
The Study Up Antrrefleiction J1Elect,Li6 Film Material On Mercury ,;Admium Telluride Infrared Detector Suafa2
Author(s):
Luo Yuanhai;
Shu Yuwen
Show Abstract
The performance of Mercury Cadmium Tellurile(MCT) infrared detecter is not only determined by electrical prameters of material, but also by the surface state of sensitive element. This paper shows, that by coating the surface of 8-12u MCT detector with an antireflecting dielectric material, reflection on the surface of sensitive element is decreased and quantum efficiency is increased therefore detectivity and responsivity are increased, usually by 15-30%.
On The Work Mechanism Of MIM Point Contact Diode
Author(s):
N. Ioli;
A. Moretti;
D. Pereira;
M. Prevedelli;
F. Strumia;
G. Carelli
Show Abstract
Many theoretical and experimental stuidies have been reported (1,2) on the metal-insulator-metal (MIM) point contact diode as a device to measure infrared optical frequencies. Electron tunnelling is the most widely accepted explanation for the extremely broadband response of MIM diodes. However, there is evidence for at least one more phenomenon, slower and possibly of thermal origin, occurring in the diode (3); this effect could be responsible of a masking effect particularly important near visible frequencies (2), where the absorption of the metals becomes greater, and tentatively contributes tc opposite polarity video detection at visible wavelengths (4). Purpose of the present work was to perform a systematic investigation on a W-Ni MIM point contact diode at different IR and FIR wavelengths. Results will be discussed which yield the determination of a cutoff for the slow mechanism and clearly demonstrate the suggested thermal origin of the effect.
Preliminary Results From The University Of Maryland X-Band Gyroklystron
Author(s):
W. Lawson;
J. Calame;
M. Skopec;
D. Welsh;
B. Hogan;
M. Naimann;
J. Renbaum;
M. E. Read
Show Abstract
The results of scaling studies for the next generation of linear electron-positron colliders have demonstrated a need for high pulse power, high efficiency, high gain microwave (8-30 GHz) amplifiers.1 As part of our investigation into the suitability of gyrotron amplifiers for this application, we are constructing an X-band gyroklystron which is predicted to achieve a peak power of 30-50 MW2. A schematic of the major subsystems of the initial two-cavity gyroklystron is shown in Fig. 1. The modulator supplies a 500 kV, 200 A, 1.5 its pulse with an intermediate voltage to a double-anode Magnetron Injection Gun (MIG). The MIG generates a rotating beam which passes through the circuit after being adiabatically compressed. The beam's phase-space distribution is modulated by a microwave signal which is injected into the first cavity. Energy is extracted axially through a coupling aperture in the second cavity and travels through a nonlinear waveguide to a half-wavelength output window. The beam expands in the decreasing magnetic field and impinges on a 35 cm section of the output waveguide. A directional coupler and water calorimeter (not shown) measure the peak and average microwave power. The nominal parameters of this configuration are listed in Table I and details of these subsystems are discussed below.
Mode Interaction In A Primed Gyrotron
Author(s):
A. H. McCurdy;
C. M. Armstrong
Show Abstract
Multi-mode operation in an overmoded gyrotron experiment is compared with the predictions of a quasi-linear theory. The different regimes of strong and weak coupling of the TE111 mode to other modes are determined. The effects of transit time broadening and beam perpendicular energy change on mode competition is investigated. The start-up of oscillation is studied in both primed and unprimed conditions. Finally the theory is used to predict the degree of mode control obtained by a driving signal of given amplitude.
85 GHz Te,Phase-Locked Gyroklystron Oscillator Experiment
Author(s):
J. M. Burke;
M. A. Czarnaski;
R. P. Fischer;
M. Gianarave;
A. W. Fliflet;
W. M. Manheimer
Show Abstract
We are studying the phase-locking of highly over-moded gyrotrons using a moderate power (~50 kW) 85 GHz two cavity TE1,3 gyroklystron oscillator. The latest experimental and theoretical results will be presented.
Feasibility Of 30 GHz Gyroklystron Amplifiers For Driving Linear Supercolliders
Author(s):
V. L. Granatstein;
W. Lawson;
P. E. Latham
Show Abstract
Operation of linear supercolliders at a frequency above the 10-17 GHz range which is usually considered would have a number of important advantages including reduced accelerator average power consumption (~w-1), and more compact microwave pulse compression circuits. Frequency scaling of gyroklystrons is especially advantageous since peak power rating of these tubes scales as w-1, while peak power per feed required by the accelerator scales as w-2. Gyroklystron amplifiers which would be suitable for driving linear supercolliders at 30 GHz are being designed.
AC Space Charge Effects In Moderately Relativistic Gyrotrons
Author(s):
P. E. Latham;
T. M. Antonsen
Show Abstract
The effects of AC space charge fields are included in the analysis of moderately relativistic gyrotrons. We adopt the slow time scale formalism developed by Antonsen, Manheimer and Levush [1] to describe the transverse self-fields while the electromagnetic fields are given by the cold cavity modes. Using a partially self consistent numerical code [2], simulations of multi-cavity gyroklystron amplifiers were performed. Preliminary studies indicate that there is an increase in both gain and efficiency. We believe that this increase in efficiency can be attributed to the relative weakness of the AC space charge field compared to the electromagnetic field: in high voltage, high current devices the interaction length is short so that the cavities do not self-oscillate. Because of the short interaction length the electromagnetic field must be large, making the AC space charge field small in comparison.
Calculation Of Limiting Current In Connection With Application To Gyrotron
Author(s):
Han S. Uhm;
Celso Grebogi
Show Abstract
The space charge limiting current in a wave cavity and in presence of electromagnetic fields is calculated in connection with application to high power gyrotrons. It is found that the ponderomotive energy alters radically the build up of beam electrostatic energy. As a consequence, the limiting current can be greatly decreased or enhanced depending on whether the ponderomotive energy is positive or negative, respecttvely. This effect can be observed experimentally and it has important practical consequences for present high-current particle beam experiments.
Nonradiative Symmetrical Dielectric Grating Waveguide For MMW DBR GUNN Oscillators
Author(s):
Zong-Wen Li
Show Abstract
In this paper a nonradiative symmetrical dielectric grating waveguide and its application to MMW DBR Gunn oscillator is presented. The width of symmetrical dielectric strips is selected carefully in order to avoid the leakage and resonance effect. A DBR oscillator has been designed and tested, Its power output is 70-100mW, and frenuency stability is better than 10-6 at 40 GHz which is 10 times better than that of MMW DBR oscillator using the inverted strip dielectric waveguide(1).
Numerical Results On Dielectric Resonators Inside Waveguides
Author(s):
A. Jostingmeier;
A. S. Omar
Show Abstract
A mode matching method for the analysis of a cylindrical dielectric resonator with arbitrarily shaped cross-section inside a waveguide is presented which allows series expansions of the fields in the region of the dielectric insert and of the waveguide with different numbers of eigenmodes. Furthermore complex modes can simply be taken into account. Resonant frequencies above the cut-off frequency of the dominant mode of the waveguide are complex due to energy radiation. The method is verified for some special cases.
Non-Linear Tlm Modelling Of High-Frequency Varactor Multipliers And Halvers11
Author(s):
S. A. Kosmopoulos;
W. J. R. Hoefer;
A. Gagnon
Show Abstract
A numerical modelling procedure in the time-domain of microstrip circuits containing non-linear devices such as varactor multipliers and halversTM is described. The two-dimensional Transmission Line Matrix (TLM) method has been extended to model elements with voltage-dependent capacitance (varactors). Waveforms and spectra computed with the TLM model compare well with measured results.
Numerical Modeling Of Generalized Millimeter-Wave Transmission Media With Finite Element And Transmission Line Matrix Methods
Author(s):
Eswarappa G. Costache;
W. J. R. Hoefer
Show Abstract
In this paper, a general finite element method as well as a graded-mesh TLM procedure for determining the dispersion characteristics, field distribution, pseudo-impedance and losses of generalized millimeter-wave transmission media are described. These methods cover arbitrary cross-sections and account for realistic features (finite metallization thickness, substrate mounting grooves etc.) that are often neglected in theoretical analysis. Dispersion characteristics and characteristic impedances obtained for dielectrically loaded ridged waveguides compare well with the available data. Conductor and dielectric losses are also computed for these structures. A modified finline structure called " ridged fin-line" is also analysed. The main advantages of this structure are its large monomode bandwidth and reduced dispersion. The cutoff frequencies of bilateral finlines in circular waveguides are also computed.
Polarization Conversions In Dielectric Strip Waveguides
Author(s):
Z. M. Lu;
S. L. Wang;
S. T. Peng;
Howard Jenkinson
Show Abstract
A new phenomenon of coflow coupling between guided waves of opposite polarizations has been discovered. Numerical results are given to illustrate the effect of polarization conversions on guiding characteristics of dielectric strip waveguides.
Analysis Of Microstrip Lines On Ferrite And Anisotropic Dielectric Substrates
Author(s):
M. R. M.L. Albuquerque;
A. J. Giarola;
A. G. d'Assuncao;
M. R.G. Maia
Show Abstract
Spectral domain analyses of microstrip transmission lines on anisotropic layers are presented. Dielectric and magnetic anisotropies are considered. The dyadic Green's function in a matrix form, in combination with Galerkin's method, are used to obtain the propagation characteristics of the microstrip on ferrite and on anisotropic dielectric substrates. Curves of effective permittivities as functions of frequency are shown for microstrip lines on anisotropic dielectric substrates.
Analysis Of Finlines On Biaxial Anisotropic Dielectric
Author(s):
F. A. F. Tejo;
A. G. d'Assuncao;
A. J. Giarola
Show Abstract
An analysis of finlines on layered biaxial aniso-tropic dielectric substrate using the finite element method is developed. The spurious modes are eliminated by imposing the restriction ∫Ω∇.Η2dΩ = 0 to the used functional with a consequent reduction of matrix size of the resultant eigenvalue problem. The basic formulation is presented and the eigenvalue equation for the calculation of the effective dielectric constant is given.
Single Mode Propagation In Magnetooptical Waveguides
Author(s):
J. Hernandez Marco;
Lluis Grau;
Lluis Torner;
F. Canal
Show Abstract
It is well known that single-mode behaviour of plane optical waveguides made of magnetooptical materials is of great importance in the implementation of an isolator. In this work we are going to analyze the propagation in a single mode magnetooptical waveguide by means of the "Transfer Matrix" method, which can be di-rectly applied to any multi-layer structure.
Making Sense Of Superconducting Infrared Sensors
Author(s):
S. A. Wolf
Show Abstract
Superconducting films have been shown to be very sensitive, broadband, low noise infrared sensors. Granular, low dimensional superconducting films of Nb, NbN, Nbn/BN as well as the high transition temperature cuprates have been studied over the last decade and shown to have unusual physical properties that make them especially suitable for use as mm-wave and infrared detectors. In this paper, this work will be reviewed with an eye toward projecting the ultimate utility of superconducting sensors
Far-Infrared Reflectivity And Magnetic Field Dependence Of High Tc Superconductors
Author(s):
Mohammed Nurul Afsar;
Hua Chi
Show Abstract
Far-Infrared reflectivity technique over the wavenumber region 10 - 800 per centimeter was utilized to observe the surface reflection of a Y-Ba-Cu-O high temperature superconductor specimen. The specimen was introduced inside a liquid helium dewar, the tail of which passes through a two inch bore Bitter solenoid high intensity d.c. magnet.
Far Infrared Reflectivity Of Ceramic High-Tc Superconductors And Of An Oriented YBa2Cu307 Thin Film
Author(s):
K. F. Renk;
W. Ose;
J. Schutzmann;
T. Zetterer;
H. H. Otto;
J. Keller;
B. Roas;
L. Schultz
Show Abstract
A far infrared study for ceramic high-Tc superconductors, T12Ba2CaCu208 and YBa2Cu307, and for an oriented YBa2Cu307 thin film is reported. We present for the ceramics, that consist of strongly anisotropic crystallites, a new method of analysis that allows to extract properties of phonons and of charge carriers. We find that the dynamical conductivity of both the ceramics and the film in the normal state can be described by Drude's theory. The reflectivity of the film in the superconducting state corresponds to a Mattis-Bardeen like behavior with an energy gap 2Δ(0)/kTc = 4.2.
Far Infrared Optical Properties Of High Tc Superconductors LnBa2Cu30X ( Ln = Y, Ho, Er, Sm, Gd, Dy, Eu, Pr )
Author(s):
S. Onari;
T. Hiroaki;
A. Ono;
S. Hidaka;
T. Arai
Show Abstract
Systematic measurements of the far infrared reflection spectra of high Tc superconductors LnBa2Cu30x for various Ln as shown in the title were performed. Infrared reflection spectra of tetragonal LnBa2Cu10, exhibit Reststrahlen vibration at 640, 590, 530, 355 and 250 cm-1, common to these materials, and the spectra of the orthorhombic LnBa2Cu30x exhibit the characteristics of free carriers except PrBa2Cupx with weak phonon structures at 617, 570, 317 and 285 cm-1. PrBa2Cu3Ox is not a superconductor, and it has no characteristic broad band due to free carriers for all x in the range of 6 to 7.
Microwave Characterization Of Bulk And Powdered High-Tc Superconductors
Author(s):
A. Meulenberg;
H-L. A. Hung;
G. H. Tough
Show Abstract
A versatile microwave/millimeter-wave characterization technique using cylindrical resonance cavities has been implemented which allows measurement of the absorption and sheet resistivity of high-temperature superconductor (HTS) powders, films, and bulk samples. Copper and YBa2Cu307_x (1-2-3) powders were compared with bulk samples to provide input for a simple model of microwave conductivity in bulk HTS materials. While the conductivity of copper metal is more than twice that of bulk YBa2Cu307_x at 77 K, the conductivity of copper powder at this temperature is less than that of the HTS powder.
RF Measurements Of High Temperature Superconducting Material
Author(s):
K. Chang;
R. K. Pandey;
M. K. Skrehot;
M. Li;
G. R. Gilbert;
K. W. Goeking;
B. L. Gries;
D. L. Mabius;
J. C. McCleary
Show Abstract
A simple RF measurement method using a resonant strip in a waveguide has been developed. The method has been used to measure the RF properties of different superconducting materials. The results of Q and loss measurements will be presented.
Characteristics And Performance Of The National Synchrotron Light Source Infra-Red. Beamline
Author(s):
Gwyn P. Williams;
Carol J. Hirschmugl;
D. Peter Siddons;
Erin A. Sullivan;
K. D. Moeller;
P. Petrone;
E. Angelides;
Y. J. Chabal;
F. M. Hoffmann
Show Abstract
The National Synchrotron Light Source (NSLS) is a very bright, pulsed, broadband IR source. Continuously covering the spectral range from the visible to the mm wave region, it has been calculated&apos 1,2 to be one to three orders of magnitude brighter than a black-body source. At wavelengths longer than 100p, (100 cm 1) the NSLS provides more flux than a standard glbbar source, due to the different power laws governing black-body radiation and synchrotron radiation emission.
Optically-Pumped NH3 Lasers - A Very Stable Frequency Source
Author(s):
J, Reid;
K. J. Siemsen
Show Abstract
A beat-note stability of 500 Hz over 1 second has been observed between two free-running optically pumped NH3 lasers. The 12 μm laser frequency is strongly isolated from cavity-mirror motion, and is relatively insensitive to perturbations in the pump lasers. The NH3 lasers have been used to observe Lamb-dips in external NH3 cells.
Pressure Effects On The Frequency Of Optically Pumped Far Infrared Lasers
Author(s):
Richard L. Crownover;
Frank C. De Lucia;
David D. Skatrud
Show Abstract
We have used millimeter/submillimeter spectroscopic techniques to investigate the pressure dependence of the absorption and gain frequencies of several optically pumped far infrared lasers. Pump offset effects on the gain frequencies were also investigated. These measurements are free from obfuscating effects such as cavity pulling and competing lasing lines which are present in measurements of oscillating laser systems.
Laser Radar Range Optimization For Detecting And Tracking Airborne Cooperative Targets
Author(s):
J. Gavan;
A. Korman
Show Abstract
A high resolution Nd-YAG pulsed Laser Radar "LIDAR" system is proposed for detecting and tracking Airborne cooperative retro-reflector carrying targets against noise, clutter and back-scatter sources. A previous range computation method is improved and new possibilities of coherent heterodyne detection and phase conjugate elements are discussed.
Initial Attempts To Observe Long Wavelength Phase Conjugation Tn An Adttptrtai Vt Dd
Author(s):
Peter A. Krug;
Dennis K. Mansfield
Show Abstract
Stable, well-dispersed suspensions of dielectric particles have been prepared for use as long wavelength artificial Kerr media. However, initial attempts at FIR degenerate four wave mixing using these suspensions have been frustrated because of the intrinsic loss of the host liquids.
Submillimeter Wave Low Temperature Admittance Of N-GaAs AND InP Diode Structures Using Transport Analysis
Author(s):
Clifford M. Krowne
Show Abstract
Numerical simulation results for n+nn+ GaAs and InP diode structures in the 1-3 THz frequency range are presented. Cryogenic temperatures from 4 through about 77 K are examined to obtain the two-terminal admittance. Earlier work has suggested possible negative differential conductivity (NDC) at or below 4.2 K, but no consistent NDC above 77 K. Implications of the Monte Carlo data for generation of submillimeter waves at these intermediate temperatures is discussed.
Analysis Of Scattering From Oil Film On Sea Surface With A Model Of Stratified Medium With Slightly Rough Interfaces
Author(s):
Sun Liguo;
Xu Shanjia
Show Abstract
A model of stratified medium with the slightly rough interfaces is presented for analysis of scattering from oil film on sea surface. Because the thickness of oil film is considered, the model is more realistic than that raised in other paper in which only single rough surface is assumed. In this paper, the coupled differential equations are derived and solved by using full wave approach, and the simple expressions of back scattering cross section for oil film on sea surface have been obtained. According to these expressions some curves are given for different thickness of oil film. It is shown that the results obtained by the present model are in better agreement with the experimental data than those obtained by single surface model.
Operation Of A Quasi-Optical Gyrotron With Variable Output Coupling
Author(s):
A. W. Fliflet;
T. A. Hargreaves;
W. M. Manheimer;
R. P. Fischer;
M. L. Barsanti
Show Abstract
Results from a quasi-optical gyrotron experiment with a 20-28 cm mirror separation will be presented showing operation from 95-130 GHz at powers up to 150 kW and efficiencies up to 11%. The output coupling can be controlled by varying the mirror separation. Efficiency optimization by variation of output coupling and by tapering the magnetic field has been demonstrated.
Nonlinear Theory Of Quasi-Optical Gyrotron With An Electron Beam At An Oblique Angle
Author(s):
C. Y. Wang;
K. E. Kreischer;
R. J. Temkin
Show Abstract
In quasi-optical gyrotrons the angle between the electron and radiation beams has considerable influences on gain, harmonic operation and efficiency. This paper investigates the effect on the efficiency. Numerical simulations show that the efficiency peaks at particular angles and is acceptable even for the seventh harmonic. So the quasi-optical gyrotron is suitable for harmonic operation.
A 120 GHz Axisymmetric Quasi Optica] Gyroiron
Author(s):
Y. Itoh;
M. Komuro;
K. Hayashi;
T. Sugawara
Show Abstract
An axisymmetric quasi-optical gyrotron was designed, constructed, and operated. Its cavity resonator was composed of a conical mirror and a plane slotted mirror. The observed oscillation frequencies were in a range from 114 to 123 GHz. Output waves were transmitted quasi-optically to a water load. The measured output power was more than 20 kW at a frequency of 120 GHz.
Design Of A Quasi-Optical Gyrotron With A Sheet Electron Beam
Author(s):
M. E. Read;
A. J. Dudas;
J. J. Petillo;
A. Drobot
Show Abstract
An electron gun has been designed to produce dual sheet electron beams to be used in a 1 MW, 120 GHz quasi-optical gyrotron. Initial design work was performed using the Herrmannsfeldt Code EGN. Final design and simulation was performed using the 3-dimensional ARGUS code. Use of a segmented sheet beam to optimize the efficiency has been examined.
"Mode Stability In A Quasi-Optical Gyrotron"
Author(s):
Wallace Manheimer;
Thomas Antonsen;
Baruch Levush
Show Abstract
The stability of modes in a quasi-optical gyrotron is examined analytically and numerically for both free running, mode locked and phase locked equilibria. One key to the analysis is the fact that the mode eigenfrequencies are nearly integral multiples of a fundamental frequency corresponding to the reciprocal of the radiation transit time between mirrors. Analytically, results are obtained with the use of a klystron model.1,2
Frequency Step-Tunable Gyrotron
Author(s):
O. Dumbrajs;
B. Piosczyk
Show Abstract
A resonator consisting of three successive cavities with different radii is proposed for a step-tunable gyrotron. Different frequencies of the operating mode can be excited in individual cavities by means of changing the beam radius and the strength of the external magnetic field. A resonator for the frequencies 120 GHz, 140 GHz, and 150 GHz, as desired by the JET, is considered for the operating mode as an example. Mode competition in this resonator is investigated theoretically.
Millimetre-Wave, Monolithic And Hybrid Integrated Circuit Technology
Author(s):
J. W. Archer
Show Abstract
Discrete devices made from GaAs have been used for many years in sensitive receivers in the microwave and millimetre-wave (mm-wave) bands (1-300 GHz). An extensive international research effort is now under way to develop GaAs monolithic integrated circuits (MMICs) for microwave and mm-wave frequencies. This paper will review recent developments in mm-wave integrated circuit technology.
Broadband Phase Modulators In Integrated Fin-Line Technique For Millimetre-Wave Applications
Author(s):
Elias Kpodzo
Show Abstract
Three structures of broadband reflection type phase modulators in unilateral fin-line are presented.The circuits have been analysed assuming ideal transmission line equivalent circuits for the fin-line sections, while the switching element,a pin-diode is represented by a typical equivalent circuit at Ka-band. The measured insertion loss is better than 1.5 dB.
GaAs Travelling Wave Schottky Contact Coplanar Wavegitide With Applications To Mimic
Author(s):
D. R. Singh;
K. S. Champlin
Show Abstract
A unique "Travelling Wave" GaAs Schottky Contact Coplanar Waveguide device has been developed which has application to MIMICs. The device is useful as wide band voltage variable phase shifter, voltage variable attenuator and frequency multiplier and has the advantage of small size, low cost and simple structure. Additionally, it also has the unique feature of incorporating the complete circuit function into one elemental device.
Optimal Design Of Millimeter-Wave Integrated E-Plane Diplexers
Author(s):
Jia Sheng Hong;
Jun Ming Shi
Show Abstract
An optimal design of waveguide E-plane diplexers for millimeter-wave applications is described. In order to increase the design flexibility and to achieve the higher performance, the dimensions of two channel filters and the spaces to the common junction are optimized at the same time according to their sensitivity information.
A Universal Test Fixture For Characterizing Mm-Wave Solid State Devices Using A Novel Deembedding Procedure
Author(s):
Robert R. Romanofsky;
Kurt A. Shalkhauser
Show Abstract
The design and evaluation of a novel fixturing technique for characterizing mm-wave solid state devices, including monolithic microwave integrated circuits, is presented. The technique utilizes a cosine tapered ridge guide fixture and a one-tier deembedding procedure to provide accurate and repeatable device level data. Advanced features include "nondestructive" testing, full waveguide bandwidth operation, a high degree of universalism, and rapid yet repeatable chip-level characterization. Furthermore, only one set of calibration standards is required regardless of device geometry.
On The Measurement Of Mm-Wave Propagation Characteristics Of GaAs Microstrip Lines
Author(s):
Robert R. Romanofsky;
Kim Adaway;
Kul B. Bhasin
Show Abstract
A thorough analytical procedure is developed for evaluating the frequency dependent loss characteristics and effective permittivity of millimeter-wave microstrip lines. The technique is based on the measured reflection coefficient of microstrip resonator pairs. Experimental data including Q factor, effective relative permittivity, and fringing for 50 Ω lines on GaAs was obtained. Effects of an imperfect open circuit, coupling losses, and loading of the resonant frequency are considered. A cosine tapered ridge guide fixture was used to characterize the resonators.
International Sample Exchange For The Comparison Of Near-Millimeter-Wave Characterizations Of Materials
Author(s):
George J. Simonis;
James R. Birch
Show Abstract
The National Physical Laboratory and Harry Diamond Laboratories have organized and are conducting an international sample exchange of materials to compare near-millimeter-wave (NMMW) characterizations made by different laboratories on exactly the same samples. The materials used comprise a cross section of NMMW properties in order to more completely test the various modes of analysis used. Results obtained up to the present and plans for the future will be provided in the oral presentation.
Solid State Spectroscopy In Far Infrared And Millimeter Wave Regions By Synchrotron Radiation
Author(s):
Takao Nanba
Show Abstract
The utilization of the synchrotron radiation from the UVSOR storage ring of the Institute for Molecular Science at Okazaki in Japan for the far infrared and millimeter wave spectroscopy has started since 1986. The experience at the UVSOR proved that the synchrotron radiation is a very bright light source over a black body source. To demonstrate the advantage to use the synchrotron radiation in the far infrared region instead of a conventional source, experiment under high pressure using a diamond anvil cell is described.
Some New Properties Of Loaded Resonators
Author(s):
Louis F. Libelo;
Guy Pisane
Show Abstract
We have been investigating the effects of loading resonator systems in the interior as well as accessing them from the exterior. We present some new properties that have been brought to light as a result of the methods used to study systems loaded in the interior. Mode charts and eigenfield distributions are to be shown for the concentric spherical resonator. The form of the representation of these mode charts illustrates the power of the techniques used and the richness of the results obtained.
Physical Processes And Development Opportunities In Far-Infrared Lasers
Author(s):
Frank C. De Lucia
Show Abstract
The physical processes of both discharge excited and optically pumped far infrared lasers will be discussed. Experimentally this work is based on the use of a tunable millimeter and submillimeter spectrometer as a diagnostic probe of the internal energy transfer mechanism in these lasers. Quantitative numerical models whose parameters describe fundamental energy transfer processes will be discussed. Emphasis will be on results which have the potential to lead to new or improved laser systems.
Optically Pumped Mid-Infrared NH3 Lasers
Author(s):
J. Reid
Show Abstract
An overview of recent experiments carried out at McMaster University on optically pumped NH3 lasers will be given. Both pulsed and cw lasers have been investigated, and conversion efficiencies - 40% have been measured. More than sixty laser transitions have been generated in the 10 to 30 μm region, with cw power as high as 10 W and pulse energies >4.5 J on the strongest lines.
Submillimeter-Wave Laser Pumped By An EMQ-Switched CO2 Laser
Author(s):
Hirokazu Shirai;
Jongsuck BaE;
Takashi Nishida;
Koji Mizuno
Show Abstract
Submillimeter wave (SMM) laser with a high peak power (> 80 W) and a high repetition rate (> 9 kHz) has been developed. The laser is pumped by a newly developed current-pulsed, mechanical shutter type Q-switched (EMQ-switched) CO2 laser. In this paper, we describe the experimental results obtained from the SMM laser pumped by the EMQ-switched CO2 laser.
Millimeter Wave CARM Amplifier Experiment
Author(s):
B. G. Danly;
K. D. Pendergast;
R. J. Temkin
Show Abstract
A high power, 140 GHz, cyclotron autoresonance maser (or CARM) amplifier is under development at the Plasma Fusion Center at M.I.T. Theory, simulations, and the experimental design are discussed. The experiment will employ a high voltage (450 - 700 kV) Pierce-type beam and a helical wiggler to produce the required electron beam. The initial experiment will be carried out using a 450 kV electron gun; the second phase of the experimental program will employ a 700 kV electron gun. First experimental operation is anticipated shortly. The details of the experimental design and theoretical analysis will be presented.
The NRL 100 GHz Cold-Cathode Carm
Author(s):
R. B. McCowan;
C. A. Sullivan;
D. A. Kirkpatrick;
S. H. Gold;
W. M. Manheimer;
A. W. Fliflet;
W. M. Black;
A. K. Kinkead;
M. Sucy
Show Abstract
The design of a 10-20 MW, 40 nsec cyclotron auto-resonance maser experiment is presented. The basic components of the CARM are a novel 600 kV, 200 A. field emission gun and a "whispering gallery" mode rippled wall cavity.
CARM EC Heating Source For High Field Tokamaks
Author(s):
Q. S. Wang;
A .T Lin;
N. C. Luhmann,Jr.;
D. B. McDermott
Show Abstract
Theory and experimental design of a 2 MW, 560 GHz CARM as well as a 1 MW, 90-140 GHz, 400 kV proof of principle experiment will be presented.
Optical Guiding In The Cyclotron Autoresonance Maser
Author(s):
Robert G. Kleva;
Baruch Levush;
P. Sprangle
Show Abstract
The effect of the electron beam on the propagation of a three-dimensional radiation beam in a cyclotron autoresonance maser (CARM) amplifier is investigated numerically. In the exponential gain regime, it is shown that the natural tendency of the radiation beam to spread diffractively is overcome and the radiation beam is focused due to the interaction with the electron beam. The nature of the focusing is found to depend on the relative magnitude of the Doppler-shifted wave frequency, wD=w-k,v, and the relativistic gyrofrequency, Ω. The radiation beam can he transported without defocusing following saturation only if wD is slightly larger than Ω. Efficiencies in excess of 50% can he attained through the use of a tapered magnetic field.
Initial Operation Of A Cherenkov CARM
Author(s):
H. B. Cao;
D. B. McDermott;
N. C. Luhmann Jr.
Show Abstract
The advantages of high efficiency and high frequency from a CARM can be obtained even with a low energy electron beam by incorporating a slow wave structure. Interaction on the light-line of a Cherenkov CARM has been achieved in an oscillator configuration.
High Power Multi-Cavity Phase-Locked Gyrotron Oscillator Experiment
Author(s):
S. H. Gold;
A. W. Fliflet;
W. M. Black;
D. A. Kirkpatrick;
W. M. Manheimer
Show Abstract
A high-peak-power 35 GHz multi-cavity phase-locked gyrotron based on a solid 1 MeV, 100 Amp, 30 nsec electron beam has been designed. The required beam transverse momentum is produced by a helical wiggler and increased to a beam pitch ratio 04.75 by magnetic field compression. The locking signal, provided by a 20 kW magnetron, drives a slotted cylindrical TE 111 prebunching cavity. The azimuthal phase bunching of the beam, is enhanced by means of a second passive bunching cavity. The TE121 output cavity, which will self-oscillate in the absence of beam prebunching, is expected to produce output powers of -10 MW and have a locking frequency bandwidth of 0.1 percent.
Analysis Of A Novel Monolithic Gaas Mis Phase Shifter
Author(s):
M. E. McKaughan;
F. C. Jain
Show Abstract
Analysis of a novel monolithic GaAs MIS phase shifter is presented. A quasi-TEM transmission line model, valid for the slow-wave regime, is used to predict operation of the device as an electronically controllable phase shifter. Device parameters such as phase shift, characteristic impedance, and insertion loss are computed.
Scattering Of Plane Wave By Microstrip Lines
Author(s):
S. T. Peng;
Robert T. Kinasewitz
Show Abstract
The scattering of a plane wave by a microstrip line is formulated under the most general conditions, including the finite conductivities of the metal strip, substrate and ground plane, in order to determine accurately the absorption of energy by the microstrip structure. It is shown that a new class of modes in the metal is needed for a formulation of the microstrip structure as a rigorous boundary-value problem by the method of mode matching.
Design And Performance Of 20 And 45 GHz Mmic Lange Couplers
Author(s):
Jack E. Wallace;
Grant A. Ellis
Show Abstract
Experimental results are presented for GaAs MMIC Lange coupler designs in both the 15 to 25 GHz and 33 to 50 GHz frequency ranges. Coupler insertion loss, return loss, isolation, and differential insertion phase are included.
FAR IR And Surface Layers (Review)
Author(s):
A. Hadni;
X. Gerbaux
Show Abstract
At a solid surface, the atoms rearrange with respect to their periodic position such as to establish equilibrium with the adjacent vacuum (I-2). Rearragement seems to go beyond the atomic scale for polar materials and experimental hints have been given by different methods (3-4-5-6-7-8-9-10).
Characterization Of The Infrared And Far-Infrared Properties Of Sapphire And Quartz
Author(s):
Michael E. Thomas;
Richard I. Joseph;
George J. Simonis;
Michael Stead
Show Abstract
High-quality room-temperature data have been obtained on single-crystal sapphire and quartz in the far infrared (ν = 50-200 cm -1) and found to follow the expected v2 variation (based on the fluctuation-dissipation theorem, e.g., Huber and Van Vleck). An extrapolation to lower frequencies following the v2 curve is found to be consistent with experimental data down to 1 cm -1. It has been physically argued in the past that the absorption mechanism in this region arises from broad phonon difference bands. We find that a substantial fraction of the observed absorption is consistent with a red-wing extrapolation from the dominant one-phonon modes seen in the reflection spectrum. A combination of these two mechanisms is believed to account for the smooth falloff in absorption that is observed.
Soft Mode Spectroscopic Study Of Ferroelectric Phase Transition In Li2Ge7015
Author(s):
Mitsuo Wada;
Akikatsu Sawada;
Yoshihiro Ishibashi
Show Abstract
Far-infrared and submillimeter wave measurements are very important in the study of ferroelectric phase transitions because the soft mode which concerns the ferroelectricity should be infrared active both in the paraelectric and ferroelectric phases.
Far IR Transmission Spectra Of Rochelle Salt At 5 K.
Author(s):
X. Gerbaux;
A. Hadni
Show Abstract
Ferroelectricity has been uncovered in Rochelle Salt (RS) by Valasek in 1920 (1). RS is a complicated crystal with four molecules [NaKC4 H4 06 , 4H2 0] in the primitive unit cell (2). Several external lattice vibrations have been observed in the 10 - 100 cm-1 far infrared range at 80 K and 5 K in crystal plates of increasing thickness : 160-550 and 6,500 μm. At 80 K absorption increases with thickness according to Beer's law. At 5 K, the lower frequency absorption line (21 cm-1) seems independent of thickness. This line had been shown to shift to a lower frequency at T = 130 K, and to disappear from the FIR range at a still higher temperature (3). More recently (4) it has been ascribed to the soft mode responsible for the FE transition with a resonant behaviour at 5 K and 80 K. It is softening into a relaxation mode whose frequency goes to zero when temperature increases up to the lower Curie temperature (T1 = 255 K). At 5 K the soft mode is a very weakly damped one, and we have to take into account the instrumental function for the discussion of the effect of plate thickness.
Measurement Of The Spectral Thermal Emission From Technical Infrared Radiators
Author(s):
A. Leupin;
H. Vetsch;
F. K. Kneubuhl
Show Abstract
We have designed a spectroscopic system for the measurement of the spectral emissivities at wavelengths between 1 μm and 16 μm of solid surfaces at temperatures from 1000 K to 1500 K. As reference infra-red radiator we have designed a blackbody whose emissivity agrees within 1% with commercial standards. We have applied our system to measure the spectral emissivities and the characteristics of blackbodies and various commercial infrared radiators.
Effect Of Temporature On IR-Absorption Of Diphenyl
Author(s):
M. I. Nasser;
M. A. Moharram
Show Abstract
In this work, the temperature dependence of the intensities of the IR absorption bands corresponding to the fundamental vibrations, overtones and combination frequencies of diphenyl is presented. A thorough discussion of the interpretation of the fundamental modes of vibration has been made on the basis of the temperature dependence of the intensities of these absorption bands. The structure of tlic. diphenyl molecule has been the subject of numerous investigations. Despite a considerable amount of work on the Raman(1),IR (3,4,5) and ultraviolet(2)spectra, the assignment of the fundamental frequencies has not yet been established with certainty, Some assistance can be obtained from the temperature dependence of the IR spectrum of this material.
Measurement Of The Dielectric Constant Of Ferroelectric Kh2Po4 At 35GHz By Transmission In A Waveguide
Author(s):
M. Horioka
Show Abstract
The apparatus to measure precisely dielectric constant of a high loss material at f=35GHz has been composed. By using this the complex dielectric constant( ε=ε-jε)of KH2PO4(KDP) has been determined in the temperature region from -160°C to 0°C. The temperature dependence of ε' shows a double peaks around the Curie temperature Tc, which characterizes the critical slowing down of the dielectric response. The maximum values of ε' and ε'' and ε'' reach 480 and 350 near Tc, respectively.
Spectroscopy And Fir Laser Emission: Periscope To The Vibrational World Of Methanol And Methylamine
Author(s):
R. M. Lees
Show Abstract
The methyl alcohol and methylamine molecules both are notable for their large-amplitude CH3 torsional motions, while methylamine has a second large-amplitude motion in the inversion or "wagging" of the NH2 group. As well, both molecules are notable in having strong infrared (IR) C-0 or C-N stretching bands which overlap well with the CO2 laser bands, and thereby provide numerous opportunities for optical pumping and FIR laser line emission. Although the torsion-rotation structure of the ground and excited state energy level manifolds is quite complex, sustained spectroscopic effort over the last decade has led to a reasonable understanding and accurate mapping of substantial portions of these manifolds. In addition to the principal species of CH3OH (1-8) and CH3NH2,(9-11) several isotopic variants of the former have been studied, including 13CH3OH (12, 13), CH3180H (14, 15) and CD3OH (16).
IR Spectra And Fir Laser Assignments For 0-18 Methanol
Author(s):
R. M. Lees;
W. Lewis-Bevan;
J. W. C. Johns;
R. R. J. Goulding;
D. P. Donovan;
C. Young
Show Abstract
The high-resolution Fourier transform IR spectrum of the C-0 stretch band of 0-18 methanol has been investigated. Assignments have been determined for a number of FIR laser lines optically pumped by CO2 lasers.
FAR Infrared Laser Assignments For Methylamine
Author(s):
R. M. Lees;
W. Lewis-Bevan
Show Abstract
High-resolution FTIR spectroscopy of the C-N stretching band of CH3NH2 has permitted location of several coincidences with CO2 laser lines, and identification of FIR laser transitions optically pumped by these lines. With the use of previous FIR spectroscopic results, it has been possible to form closed frequency combination loops to support the assignment of one of the IR-pump/FIR laser transition systems and improve the accuracy of one of the FIR laser frequencies.
Experimental Results On Relativistic Gyrodevices
Author(s):
R. B. McCowan;
S. H. Gold;
W. M. Black;
W. M. Manheimer
Show Abstract
Experimental work at the Naval Research Laboratory has proceeded on three different relativistic gyrodevices, the cyclotron autoresonance maser (CARM), the three cavity phase-locked gyrotron oscillator, and the high power free running gyrotron oscillator. Experimental results relating to these projects will be presented.
Intense Electron Beam Cyclotron Masers With Microsecond Pulselengths
Author(s):
R. M. Gilgenbach;
J. G. Wang;
J. J. Choi;
C. A. Outten;
T. A. Spencer
Show Abstract
Experiments have been performed in which MW microwave power levels have been produced by means of the cyclotron maser resonance on high current, relativistic electron beams from a generator with parameters: 0.4 MV,1.2 kA, and 0.4 gs. In the first series of experiments, a nonadiabatic dip in the magnetic field imparted large ratios of perpendicular to parallel momentum (a >1) in a transported beam current of typically 20 - 60 A. X-Band microwave power (>0.6 MW) was sustained over nearly the full e-beam pulselength and 85% variation in electron beam generator voltage. In more recent experiments, MW power levels in X-band have been generated using an improved magnetic field profile which increased the transported electron beam current to 500 - 1000 A, but with lower a (0.2 -0.3). A wiggler has been utilized to increase the ratio of perpendicular to parallel momentum. Data show a strong (up to a factor of 40) enhancement in peaks of K-band microwaves when the e-beam energy is near a resonance condition with the wiggler. Design studies are underway for a multimegawatt, microsecond, intense electron beam cyclotron maser which will operate on the Michigan Electron Long Beam Accelerator (MELBA) at parameters: 0.7-1 MV, 1-10 kA, and voltage compensated pulselength of 1-1.5 gs.
Experimental Investigation Of The Effects Of A Neutralizing Background Plasma On The Operation Of A High Current Gyrotron
Author(s):
D. A. Kirkpatrick;
S. H. Gold;
A. K Kinkead;
W. M. Manheimer;
C. A. Sullivan;
T. M. Antonsen;
B. Levush
Show Abstract
We present plans for an experiment to investigate the effects of a neutralizing background plasma on the operation of a high current gyrotron. A neutral plasma filling the electron beam transport and gyrotron cavity regions allows for the propagation of super-vacuum currents and for tuning of the interaction frequency through the neutralizing plasma density. The background plasma is completely ionized before the passage of the high current electron beam, and the plasma, density(in the absence of the electron beam) is a known, measured quantity.
Design Of A 100 KW Gyro-TWT
Author(s):
C. S. Kou;
D. B. McDermott;
C. K. Chong;
N. C. Luhmann Jr.
Show Abstract
A gyro-TWT is often plagued by absolute instabilities in lower order modes and even in the operating mode itself. These problems will be avoided by performing the experiment in the lowest order mode in cylindrical waveguide ( TE 11 ) and using a low a beam to excite a wave with large kn. A gyroresonant wiggler will partially transform the axial velocity of a high quality Pierce beam into transverse velocity. A 100 keV, 5 A, = 0.5 beam will generate 9 GHz rf in a 3 kG magnetic field. Magnetic tapering will be used to enchance the efficiency. The theoretical gain is predicted to be 60 dB with a bandwidth over 20%.
Efficiency Enhancement In Gyro-Bwo By Tapered Magnetic Field
Author(s):
A. K. Ganguly;
S. Ahn
Show Abstract
A three dimensional self-consistent theory of the gyrotron backward wave oscillator has been developed in slow-time-scale formulation. The efficiency of gyro BWO is nearly 10% in a uniform magnetic field but can be enhanced to exceed 25% by tapering the magnetic field. Results are shown for TE10 mode in rectangular waveguide and TE11 mode in cylindrical waveguide.
Operation Of A 140 GHz Tunable Backward Wave Gyrotron Oscillator
Author(s):
W. C. Guss;
K. E. Kreischer;
R. J. Temkin;
M. Caplan;
D. Pirkle
Show Abstract
A tunable backward-wave oscillator (BWO) gyrotron is currently being operated at MIT which is a prototype for a FEL driver at high frequency. Novel features of this design, are the overmoded TE12 cylindrical cavity, a wide band moth-eye window, and the use of a Pierce-wiggler gun. The design objectives are voltage tuning from 130-140 GHz with 10 kW output power. The interaction region is 10λο long where λο is the free space wave length. A linear 2° uptaper is used to maintain mode purity and a broadband motheye window is used for maximum transmission.
An Experimental Sixteenth Harmonic Cusptron Device
Author(s):
S P. Kuo;
K. K. Tiong;
P. E. Miller
Show Abstract
A cusptron device operating at sixteenth cyclotron harmonic has been set up for the development of a compact and high power microwave source. An axis-encircling electron beam of 22Kev (=1.044) as the radiation source is produced from an annular thermionic cathode of 1.4 cm radius and 0.16 cm radial thickness with a pierce-type focusing electrode together with a cusp magnetic field. A 16-slotted waveguide with b/a=1.23 is used for the 2π mode operation where b and a are the radii of the slots and the inner wall of the waveguide respectively. a=1.7 cm is designed so that the operating magnetic field is 364 Gauss and the radiation frequency is 15.6GHz. 11% efficiency is achieved from particle simulation. The results of our experimental study will be presented and a comparison of the experimental results with those of particle simulation will be made.
Resonator With A Curved Wall For A Gyrotron
Author(s):
O. Dumbrajs;
H. Wenzelburger
Show Abstract
The influence of the curvature of the resonator wall on the frequency, quality factor, efficiency, current and the optimum magnetic field is studied within the framework of a simple resonator model for a gyrotron operating at 150 GHz in the TE03 mode with the output power 200 kW.
Millimeter-Wave Suspended Parallel-Coupled Filters At Ka And W-Band
Author(s):
Thomas Chen-Chou Ho;
Kan Chou
Show Abstract
The design and development of Ka-band (26.5-40 GHz) and W-band (75-110 GHz) parallel-coupled filters with suspended stripline structure is described. The measured insertion loss at the passband is about 1 dB for Ka-band and 2 dB for W-band. The return losses are more than 12 dB in the passbands for both frequency bands.
Printed-Circuit Rat-Race-Type Directional Couplers For Larger Power-Split Ratio
Author(s):
Isao Ohta;
Ichiro Hagino;
Takenori Kaneko
Show Abstract
Two different types of 5/2-wavelength rat-race-type directional couplers with a remarkably increased power-split ratio for a realizable ring-impedance, in particular which are useful for millimeter-wave circuits suffering from the severe restriction on the usable impedance range, are described. Experimental corroboration is provided in the microwave region (at 8 GHz).
Circulator Using Gaas Dual Gate FETs
Author(s):
Sachihiro Toyoda
Show Abstract
This paper describes active circulators for microwave band. Using three dual-gate FETs, a 2 GHz band circulator was constructed. The bandwidth of this circulator is 1.3 GHz, and the insertion loss and the isolation are 0.3 dB and 30 dB, respectively. Further, the circulator for 5 - 18 GHz band is proposed and tested. Three amplifiers for 5 - 18 GHz and three power dividers' are used. The frequency range of this circulator is from 5 to 18 GHz. The circulator exhibit the insertion loss of 0.3 dB and the isolation of 30 dB. The circulator for 5 - 18 GHz band can be used for the input power up to 19 dBm.
A Simple And Low Cost 3-Probe Measurement Technique Using Microstrip Circuits
Author(s):
Kai Chang;
Ming-Yi Li;
Thomas Sauter
Show Abstract
A simple and low cost measurement system using 3-probe microstrip circuits has been developed for impedance and S-parameter measurements. The coupling coefficients for the three probes can be unequal and only one power meter is required. The measured results agree very well with those obtained from an HP 8510 automatic network analyzer.
Experimental Results Of A High Q Quasi-Optical Reflection Cavity
Author(s):
Karen A. Lee;
Margaret A. Frerking
Show Abstract
A quasi-optical reflection cavity has been designed, constructed, and tested and consists of three elements in cascade: a high Q folded Fabry-Perot resonator, a lower Q Fabry-Perot resonator, and a diffraction grating. The resonator exhibits a Q of 6700 and 1.6 dB of loss at 63 GHz. The design can be scaled to 1 THz to serve as the resonator for high frequency quantum well resonant tunneling device oscillators.
CW Doppler Systems For External Urodynamic Study, Comparison Between Electromagnetic Wave And Airborne Ultrasound
Author(s):
Y. Takeuchi
Show Abstract
Urination behavior indicates a series of important information for urologist Doctors, to find, for example, prostatic hypertrophy. External, non-contact urodynamic monitors using CW-Doppler principle were built in similar wavelengths with 24GHz electromagnetic wave (λ=12.5mm) and 40KHz airborne ultrasound (λ8.5mm). Both. systems were found having almost equivalent excellence in detecting the Doppler return from. urinary flow simulated by water ejector. However, airborne ultrasound system. seems slightly less expensive although its electronics are more complicated.
Development Of A Broadband 3 -mm PHF H- Plane Wavegu Ide Circulator
Author(s):
Zhang Dengguo;
Wu Zhengde
Show Abstract
The exact operation mode of PHF H-plane waveguide circulator is given to be HE, where L=n+8x=1 n=0,1,2,.... and 8 can be determined numerically. A broadband 3-mm circulator operating in the lowest mode HE118 is reported for the first time. The center freguency of waveguide circulator agrees well with the resonance frequency of the dielectric ferrite resonator if no magnetic bias is applied(1). At r=R1 and r=R2 in Fig.1.
Determination Of I-V Characteristics Of Negative Conductance Devices From Microwave Reflection Coefficients
Author(s):
P. Huang;
A. Botula;
N. C. Luhmann Jr.;
D. S. Pan
Show Abstract
Negative differential conductance (NDC) devices have stimulated intensive research activities since the first acknowledged work on the tunnel diode, also referred to as the Esaki diode l. In recent years, the interest in NDC devices has been revived by the successful fabrication of various double barrier resonant tunneling (DBRT) structures 2,3. The interest in these DBRT structures is due primarily to their high potential as high frequency devices. For the design of high frequency devices, the necessary information is provided by the detailed shape of the dc I-V characteristics, especially the negative conductance regime. Unfortunately, the NDC regime of the I-V curve has always made the dc I-V measurement difficult because of its nature to oscillate. A direct dc measurement of the I-V characteristics by a conventional curve tracer only shows the positive conductance portion of the entire I-V curve. Various methods have been proposed to measure the I-V characteristics.
Submillimeter Wave Emission From Semiconductor Superlattices
Author(s):
M. Helm;
E. Colas;
P. England;
F. DeRosa;
S. J . Allen Jr.
Show Abstract
Far infrared emission due to electronic transitions between subbands in semiconductor superlattices is observed for the first time. The electrons are excited by applying an electric field in the plane of the layers. The generated radiation is coupled out of the sample by a metallic grating on the surface.
Far Infrared Non Astigmatic Czerny-Turner Monochromator For Stressed Ge:Ga Photoconductor Experiments
Author(s):
N. Hiromoto;
H. Takami;
T. Itabe;
H. Okuda;
H. Matsuhara;
H. Shibai;
T. Nakagawa
Show Abstract
A far infrared monochromator of Czerny-Turner type has been devised which has an output optical system comprising two small spherical mirrors to obtain non-astigmatic image. The far infrared monochromator covers both 50-120 um and 100-240 um wavelengths ranges and can be used to measure spectral response of stressed Ge:Ga photoconductors having response up to 200 um, which we have fabricated to apply them to far infrared astronomical observations by balloons and by sattelites. Experimental performance of the stressed Ge:Ga photoconductors under low photon fluxes conditions also will be given.
High Frequency Semiconductor Heterostructure Device Analysis
Author(s):
Clifford M. Krowne;
Gregory B. Tait
Show Abstract
Two-terminal heterostructure diodes present many potential opportunities for high frequency operation, even into the millimeter wave frequency regime. Motivated by this fact, we have developed an algorithm which is globally convergent for solving the nonlinear Poisson equation. By appropriate numerical techniques, the nonlinear Poisson equation is coupled to the current continuity equations which can then be employed for high frequency, small signal, ac simulations. Numerical results for the AlyGa1-yAs system with layers as thin as a few hundred angstroms in thickness are provided.
Far Infrared Absorption Spectra Of Amorphous (As2S3)- (Sb2S3) Semiconductors And The Spatial Charge Fluctuation
Author(s):
K. Matsuishi;
T. Anzaki;
S. Onari;
T. Arai
Show Abstract
Far infrared absorption spectra of amorphous (As2S3) 1-x(Sb2S3)x system (x=0.0-0.6) were measured in the wavenumber region 7-25 cm-' with Lamellar grating far infrared Fourier Transform Spectrometer, and the spatial fluctuation of charges and its correlation range were estimated with charge fluctuation model. The charge fluctuation of (As2S3)1-x(Sb2S3)x system increases with Sb2S3 concentration x. On the other hand, the correlation length of the charge fluctuation decreases from 7 A to 4.5 A with an increase in x. As a result, it can be found that the medium range order of As2S3 changes drastically with an increase in Sb2S3 concentration x.
Effects Of Annealing On The Electrical Properties Of P-Cd0.2Hg0.8Te Grown By LPE
Author(s):
K. Yasumura;
K. Sato;
Y. Yoshida;
Y. Komine
Show Abstract
The effects of annealing on the electrical properties of Cd0.2Hg08Te(CMT) grown by liquid phase epitaxy technique are investigated. We show that the annealing at the temperature as low as 250°C under the vacuum condition is superior to the conventional technique, annealing at the temperature higher than 400°C under Hg over-pressure, to obtain high quality p-CMT layers. Hole concentration and mobility of the resultant p-CMT are 7.2x1015cm-3 and 787 cm2/V•sec, respectively.
Millimeter And Submillimeter Wave Optical And Dielectric Properties Of Single Crystal High Purity Silicon
Author(s):
Mohammed Nurul Afsar
Show Abstract
The single crystal silicon is a monatomic material. The lattice vibration absorption peaks appear around 18,000 GHz (600 wavenumber per centimeter). The only other absorption process present in the entire millimeter and submillimeter wave region is the free carrier absorption which centers around 60 GHz (5 mm in wavelength, 2 wavenumber per centimeter). The free carrier absorption can be reduced in two way: by making the material ultra pure or by introducing deep trap impurities while manufacturing. The resistivity increases in both cases. Complex refractive index, complex dielectric permittivity and loss tangent spectra on several hyperpure silicon specimens will be presented as a function of frequency and resistivity and compared.
Band Dege Structure Of Pb1-XsnxTe Doped With Indium By Far-Infrared Magnetoplasma Reflection Method
Author(s):
S. Takaoka;
S. Shimomura;
H. Takahashi;
K. Murase
Show Abstract
Far-infrared magnetoplasma reflection spectra of In doped Pb1-xSnxTe are measured across the band inversion region (0.15<x<0.40). From the spectra, the temperature dependeces of photo-carrier concentrations and cyclotron masses are determined below 20K, where large photoconduction is observed. By using the two bands theory with observed masses and carrier concentrations, it is found that the band edge masses become much heavior even by 1% In doping, while the band gaps do not change appreciably as compared with those of undoped Pb1-xSnxTe.
Low Frequency Impurity Vibration Modes In II-VI Semiconductor
Author(s):
Lu Wei;
Ye Hongjuan;
Xu Wenlan;
Shen Xuchu;
W. Giriat
Show Abstract
The quasi-local modes induced by light impurities in CdTe and observed by use of the far infrared spectroscopy have been reported. The theoretical analysis of these modes by combining the Green's function with Recussion calculation has shown an obvious acoustic phonon behavior of quasi-local modes.
Novel Aspects Of Far-Infrared Gas Lasers
Author(s):
Fritz K. Kneubuhl
Show Abstract
A review is given on actual applications of far-infrared gas lasers in basic laser physics. These concern the various aspects of distributed feedback and deterministic chaos.
Theory Of Optically Pumped Fir Lasers
Author(s):
Lin Yikun
Show Abstract
So far, the optically pumped FIR laser was a useful and cheap coherent source for FIR techniques. The drawbacks of this kind of laser source are: (1) Provides only discrete FIR discrete FIR spectral lines. (2) It lase with relatively low efficiency. (3) It occupies too large space as compared with the conventional electronic equipments. In this review, the theory of optically pumped FIR laser actions in the multi-level quantum system will be introduced as follows:
Line Selection In Off-Resonantly Pumped Systems
Author(s):
M. A. Dupertuis
Show Abstract
The problem of line competition in off-resonantly pumped systems is reviewed. The theoretical predictions are compared with recent experimental results in the FIR.
The Inverse Smith-Purcell Effect At Submillimeter Wavelengths
Author(s):
J. Bae;
K. Furuya;
H. Shirai;
T. Nishida;
T. Nozokido;
K. Mizuno
Show Abstract
The inverse Smith-Purcell (ISP) effect is a candidate for laser-driven linacs with an accelerating gradient of several GeV/m. It uses a metallic grating as an interaction circuit. For the first time, we observed the ISP effect using a submillimeter wave (SMM) laser as the driving source in 1987. Since then, we have improved the signal-to-noise ratio in the electron energy measurements to verify the theoretical predictions in more detail. In this paper, we describe our experimental apparatus and newly obtained experimental results of this effect. These agreed with the theory.
Copper And Molybdenum Mirrors For High Power TEA CO2 Laser
Author(s):
Y. Tsunawaki;
K. Yoshida;
K. Ohta;
S. Aramaki;
H. Okamoto;
M. Yamanaka;
S. Nakai
Show Abstract
Various kinds of copper (Cu) and molybdenum (Mo) mirror were studied on the damage induced by a TEA CO2 laser. Cu mirror had a damage threshold-2 to 2.4 times higher than that of a Mo mirror. As suggested in the previous work 1), a single-crystalline mirror was stronger than a poly-crystalline one while TEA CO2 laser was irradiated onto the mirror surface, because most of the damages originated at the grain boundaries of the poly-crystalline surface.
Microwave And Milliiikter-Wave Spectra Of 13CD3OH
Author(s):
K. V.L.N. Sastry;
I. Mukhopadhyay;
R. M. Lees;
J. VanderLinde;
D. Donovan
Show Abstract
The microwave absorption spectrum of 13CD3OH has been investigated in the frequency region 18-80 GHz. The a-type R-branch transitions have been measured for J=1-0 and J=2-1 for the lowest three torsional states. Asymmetry splittings were observed for the K=1, A transitions. In addition, frequencies have been measured for a substantial number of b-type transitions, including the K=1-0 El and K=3-2 A Q branches. The frequencies have been fitted to a semi-empirical torsion-rotation model, and a-type and b-type parameters are reported. Stark effect measurements were made for the J=1-0 A and E transitions in the three lowest torsional states, and J=3-2 El in the ground torsional state.
A Broadband Gyro-TWTA Experiment
Author(s):
S. Y. Park;
R. H. Kyser;
C. M. Armstrong;
A. K. Ganguly;
R. K. Parker
Show Abstract
A tapered reflection-type gyrotron amplifier(33kV, 1.2A) has been designed and built. The amplifier incorporates precise axial tapering of both the magnetic field and the interaction circuit for stable broadband operation(27-34 GHz). Cold test results show that the tube presents an excellent RF match over the entire operating band. This device will be used to explore the performance characteristics of low voltage operation.
High Current Density Cathodes For Microwave Tubes
Author(s):
M. E. Read;
A. J. Dudas;
P. E. Oettinger
Show Abstract
There has been a recent resurgence in the research and development of high power microwave sources, spurred by the growth of pulse power technology, wherein advances in energy storage and pulse forming have made possible the generation of electron beams with peak powers over 4 Terawatts. These beams can generate microwaves and millimeter waves with impressive intensity over a wide frequency range. Unfortunately, these high peak powers have been achieved, with few exceptions, with pulse lengths less than 100 ns, and, therefore low energy content. Moreover, the pulse repetition rate has been very low, with a measured peak of approximately 50 Hz. Such limitations in pulse length and repetition rate have been due to the characteristics of the accelerators and the nature of the cathode sources of the electron beams. However, lately, significant advances have been made in accelerator technology allowing the generation of pulses with microsecond pulse lengths and peak powers of 10 GW.
A Non-Adiabatic Electron Gun For Gyrotrons
Author(s):
B. Piosczyk
Show Abstract
The hollow electron beams in gyrotrons are normally generated in magnetron injection type (MIG) guns1. In these guns the transverse velocity of the electrons is mainly determined by the ExB-drift at the emitter. Non-adiabatic effects during the acceleration do not give a major contribution. Several properties of the electron beam, such as the sensitivity to space charge effects and to conditions of the emitter surface, are related to this kind of extraction.
Frequency Domain Analysis Of A Gyrotron
Author(s):
E. Jensen;
K. Schunemann
Show Abstract
For this analysis, the gyrotron is divided into an active, nonlinear "amplifier" and a passive, linear "resonator" part. At the interface between these parts, voltages and currents may be defined from modal expansion. Both the linear and the nonlinear network are then characterized by immitance matrices. The method is applied to a sample gyrotron.
Experiments With A 35 GHz Cyclotron Autoresonance Maser (CARM) Amplifier
Author(s):
G. Bekefi;
A. DiRienzo;
C. Leibovitch;
B. Danly
Show Abstract
Studies of a cyclotron autoresonance maser (CARM) are presented. The measurements are carried out at a frequency of 35 GHz using a mildly relativistic electron beam of 1.5 MeV energy and a 200 A current. The beam is generated by a field emission electron gun followed by an emittance selector that removes the outer, hot electrons. The entire system length (~2.0 meter), including the field emission gun, is immersed in a uniform solenoidal guide field of 7 kG. Perpendicular energy is imparted to the electrons by means of a bifilar helical wiggler having a period of 7 cm and a length of 56 cm. The cyclotron radiation is generated in a 1 meter long wiggler free region. Initial superradiant measurements give a small signal gain of 91 dB/m. Experiments are also underway in which a 35 GHz, 100 kW magnetron is used as the driver for our CARM amplifier.
Operation Of Harmonic Gyrotrons In The Submillimeter Region
Author(s):
S. E. Spira;
K. E. Kreischer;
R. J. Temkin
Show Abstract
High power, submillimeter, second harmonic emission has been achieved with a 10 A, 75 kV, 1μ, sec pulse electron gun. In an iris cavity configuration, using a motheye window, second harmonic modes were observed at 12 frequencies in the range 301-503 GHz, with 15 kW at 417 GHz and 4-7 kW at 9 of the other modes.
Non-Linear Analysis Of A Gyro-Peniotron Oscillator
Author(s):
P. Vitello
Show Abstract
We present here the results of a non-linear numerical investigation of a high-harmonic gyro-peniotron oscillator design which uses a slotted cylindrical magnetron-type cavity. Our modeling shows that very high efficiency ( 60%) can be achieved at high harmonics (s > 3), and that the operation current can be dramatically reduced by the addition of slots. We find that the start oscillation current may decrease with harmonic number in a slotted device, unlike the smooth walled gyrotron where start oscillation current always increases with increasing harmonic number. This greatly favors the use of a slotted cavity for high harmonic operation. The gyro-peniotron oscillator in a slotted cavity appears attractive as a means of achieving millimeter wave emission.
Prebunched High Harmonic Gyrotron
Author(s):
C. S. Kou;
D. B. McDermott;
N. C. Luhmann Jr.
Show Abstract
A prebunched beam has been used to further increase the efficiency of our axis-encircling high harmonic gyrotron. The experiment was performed at the third harmonic with a TE312 mode at 27.7 GHz. The conversion power was 6.7 kW which was significantly greater than that of the non-prebunched experiment. Also, mode competition was substantially reduced. The dependence of the output power on the square of current has been verified . The start of oscillation current is effectively zero.
Linear Analysis Of The High-Power Magnetron
Author(s):
R. A. Stark;
H. S. Uhm
Show Abstract
A linear stability analysis of the extraordinary mode in a high-power (>GW) planar magnetron is developed using a cold-fluid model of the electron flow. The eigendifferential equation for arbitrarily intense electron flow is found and solved numerically through finite differencing techniques. As a sample of some initial results, a calculation of growth rates versus cavity depth is shown.
Symmetry And Periodicity For Millimeter Wave Devices
Author(s):
W. N. Cain;
R. W. Grow
Show Abstract
Symmetry and periodicity is discussed as it pertains to wave propagation, with particular emphasis on Floquet's theorem and Bloch's theorem. Floquet's theorem in three dimensions is applied to a circular waveguide with screw periodicity. The resulting dispersion characteristics of the uncoupled modes are compared to those of a normal circular waveguide.
Microwave Losses In High Tc Superconducting Microstrip Ring Resonators
Author(s):
June Takemoto;
Floyd Oshita;
Harold Fetterman;
Paul Kobrin;
Emilio Sovero
Show Abstract
Microwave properties of high Tc superconducting films sputtered on MgO were measured using a closed-loop ring resonator circuit. Unloaded Q values of Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O resonators were compared to gold plated resonators of identical design. The attenuation of yttrium-barium-copper oxide films on a MgO substrate is approximately 31% lower than gold films at 6.6 GHz and 33% lower at 19.2 GHz for temperatures below 50 K.
Microwave Phase Conjugation In Artificial Kerr Media
Author(s):
Robert Shih;
Harold R. Fetterman;
Bradley Bobbs;
William W. Ho;
Robert McGraw;
Dan Rogovin
Show Abstract
One dimensional phase conjugation of microwaves via degenerate four-wave mixing in an artificial Kerr medium has been demonstrated. The medium consisting of a liquid suspension of elongated graphite particles is confined within a single mode waveguide. The decay of the nonlinear refractive index grating is shown to agree with previous relaxation time measurements.
Magnetopolaron Effects In CdTe
Author(s):
J. Oberti;
M. Goiran;
M. Bouchelagem;
R. Triboulet;
J. Leotin
Show Abstract
The electron cyclotron effective mass in CdTe was measured with photons having energy ranging from 12 to 250 cm 1. The expected dramatic decrease of the mass when the photons energy exceeds that of the LO phonons is shown for the first time. Accurate measurements at 4K were made possible by a free carrier persistent effect occuring in the samples investigated. The magnetic field resonance values at various photons excitation energies were fitted by using a recent accurate calculation of the magnetooptic absorption by Peeters and Devreese. This new theory produces a good fit with the data when taking the electron Frolich constant value ∝ = 0.3 and adjusting the band mass to the value mb = 0.092 m0. Previous results and theory favours the values ∝ = 0.4 and mb = 0.089mo.
Quantum Limit Electron-Phonon Scattering Studies In Semiconductors By Far-Infrared Cyclotron Resonance
Author(s):
H. Kobori;
T. Ohyama;
E. Otsuka
Show Abstract
Extensively systematic studies of the cyclotron resonance linewidth in the quantum limit have been performed on electron-phonon scattering in basic semiconductors ( Ge, CdS, GaAs ). Far-infrared (119 to 513 μm) laser cyclotron resonance experiments have been carried out in photo-excitation by pulsed band gap light or in thermal excitation. We present the temperature and magnetic field dependences of cyclotron resonance linewidth for electron-phonon scattering in the quantum limit with respect to various samples.
Far-Infrared Cyclotron Resonance Studies Of Impurity Scattering In Ge, GaAs And InSB
Author(s):
Hiromi Kobori;
Tyuzi Ohyama;
Eizo Otsuka
Show Abstract
Contribution of impurity scattering to the electron cyclotron resonance linewidth (inverse relaxation time) has been studied in the quantum limit, after subtracting the contribution of phonon scattering, for typical semiconductors Ge, GaAs and InSb. To our surprise, dependence of inverse relaxation time on temperature, magnetic field and impurity concentration is the same for neutral and ionized impurities.
Broadband Dielectric Measurements With Picosecond Transient Radiation
Author(s):
G. Arjavalingam;
Y. Pastol;
J.-M. Halbout;
G. V. Kopcsay
Show Abstract
Picosecond transient radiation from optoelectronically pulsed integrated antennas is used for coherent microwave spectroscopy in the 10 to 125 GI Iz frequency range. The experimental apparatus is characterized using samples with predictable loss and dispersion properties. We present measurements of the frequency dependent absorption coefficient and refractive index of materials performed using this set-up.
Millimetre-Wavelength Pulse Propagation Through The Earth's Atmosphere
Author(s):
C. J. Gibbins
Show Abstract
The effects on pulse propagation at millimetre wavelengths of both atmospheric absorption and dispersion are calculated. For subnanosecond pulses, severe broadening of the pulse occurs at frequencies near to atmospheric absorption lines, whilst around the centres of such lines, in regions where the second derivative of the absorption coefficient is negative, pulse compression is found to occur. Furthermore, the frequency at which maximum energy in the pulse is received shifts from the carrier frequency towards regions of lower atmospheric attenuation, while the pulse itself acquires a modulation in the form of a chirp frequency.
Statistics Of Propagation At Millimetric, Infrared And Optical Wavelengths
Author(s):
C J Gibbins
Show Abstract
This paper describes the results of an investigation into the statistics of propagation measurements made at millimetric, infrared and optical wavelengths over a 500m path. The analysis includes an evaluation of the distribution of attenuation levels and rainfall rates exceeded during the 12 month period analysed, together with an examination of the distribution of fades and rainfall rates of various durations and intensities, and the return periods between such events.
Far-Infrared Detector Using BaPb0.7Bi0.3O3 Thin Film Josephson Element.
Author(s):
A. Sawada;
X . Sato;
Y. Enomoto;
T. Murakami
Show Abstract
A new detector using BaPb0.7 Bi0.3 03 thin film Josephson element has been found to detect far-infrared light in the range of wavelength from 50μ to 500μ (wavenumber from 200 cm -1 to 20 cm -1). The optimum conditions are searched by changing the temperature of the element, the bias current through the element, and the chopping frequency of incident light.
Coherent Mechanical Fir Doppler Shifting For Heterodyne Applications
Author(s):
U. H. W. Lammers;
R. A. Marr;
J. B. Morris
Show Abstract
Frequency shifting of a single far infrared laser source by mechanical means is investigated to obtain highly correlated transmit and local oscillator signals for narrowband heterodyne reception. The analysis refers to a radar but applies to other systems as well.
Self-Consistent Transmission Line Analysis Of The Gyrotron Traveling-Wave Amplifier
Author(s):
J. E. Arrington;
R. W Grow;
J. M. Baird;
L. R. Barnett
Show Abstract
A self-consistent analysis of the gyrotron traveling-wave amplifier is performed using a single particle theory and an exact transmission-line field analysis to yield a nonlinear large signal theory able to describe the effects of tapered, nonideal wall waveguides and tapered dc magnetic fields. Guiding center drift is considered, as well as efficiency as a function of input power, RF detuning, de detuning, current, and beam size.
In-waveguide TE01-to-whispering gallery mode conversion using periodic wall perturbations
Author(s):
Manfred Thumm;
Annemarie Jacobs
Show Abstract
This paper reports numerical optimization calculations on
mode converters to generate pure, rotating TE 1,2,3 (at
120 GHz) and TE 15,2 (at 140 GHz) whispering gallery modes
(WGM) in oversized circular waveguides, for conversion efficiency
optimization studies on high-power quasi-optical WGM
gyrotron output mode transducers. Two-stage TE01-to-TEonto-
TEm2 conversion sequences (n = 6 at 120 GHz, n = 7 at
140 GHz) using periodic radius and m-fold helical (corkscrew
type) wall deformations, respectively, provide output mode
purities of almost 99%.
The direct conversion to a Gaussian beam from TE03 Gyrotron modes
Author(s):
H. J. Barkely
Show Abstract
The use of quasi-optical Vlasov converters to produce
directly Gaussian output beams from TEo3 waveguide
modes has been studied at 70 GHz. The farfield
measurements presented here of various types
of these converters, with and without their parabolic
mirrors, indicate inherent efficiency limitations
in the simplistic design originally proposed.
Window materials for 280 GHz continuous wave gyrotron
Author(s):
Mohammed Nurul Afsar
Show Abstract
The high frequency absorption in crystalline and polycrystalline materials
arises mainly from sharp lattice vibrations, or due to the tail effect of the intense
lattice vibration absorption peak. In polycrystalline material there are also other
sources of absorption such as amorphous region continuum. A monatomic
material such as diamond or diamond like silicon has a simple cubic structure and
the lattice vibration absorption peak appears at a very high frequency (Infrared
frequency region 20,000 - 40,000 GHz). The 280 GHz region is then completely
free from the tail effect of lattice vibration absorption peak. If one can prepare a
specimen of such a material in which other millimeter wave absorption processes
are compensated, the window will have negligible absorption at 280 GHz.
Small-signal analysis of a free electron cyclotron resonance laser
Author(s):
Changbiao Wang
Show Abstract
The free electron cyclotron resonance laser, based on conversion of synchrotron radiation to a coherent oscillation, operates at an extremely hight harmonic with a frequency of about .39, with the transverse relativistic factor and wc the relativistic cyclotron angular frequency. By introduction of the field amplitude spontaneous modified coefficient and by local expansion of the interaction light field, the linear efficiency and the start-up current are derived. It is shown that this device possesses a striking narrow width of the efficiency profile and so can successfully oscillate on a single longitudinal mode to produce light output of good coherence.
