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Proceedings Volume 0733

Soft X-Ray Optics and Technology

E. Koch, Guenther A. Schmahl
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Proceedings Volume 0733

Soft X-Ray Optics and Technology

E. Koch, Guenther A. Schmahl
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Volume Details

Date Published: 1 January 1986
Contents: 1 Sessions, 74 Papers, 0 Presentations
Conference: Soft X-Ray Optics and Technology 1987
Volume Number: 0733

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Table of Contents

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Plasma Sources and X-ray Lasers
Pierre Jaegle, G. Jamelot, A. Klisnick, et al.
Using hot plasmas for making soft X-ray amplifiers will lead to laboratory sources brigther than any others by several orders of magnitude. Population inversions are produced either by collisional pumping due to plasma free electrons or by fast plasma cooling. Gain coefficients up to 5 per cm have been measured in the 100 A - 200 A range.
Laser-plasma XUV sources generated by KrF lasers
F. O'Neill
Recent developments at the Rutherford Appleton Laboratory on the use of 249nm KrF lasers for generating laser-plasma XUV sources are reviewed. XUV sources are produced using both a high energy (200J, 5Ons), purpose-built single shot laser and a low energy (0.7J, 25ns), repetitive(1 Hz) commercial system. These new sources have been applied to experiments in the areas of X-ray microscopy and X-ray lithography.
Efficient Soft X-Ray Generation In Short Wavelength Laser Produced Plasmas
T. Mochizuki, C. Yamanaka
Intense x-ray generation in 1.053, 0.53, 0.26 µm laser-produced plasma has been investigated in the photon energy range of 0.1 to 3keV. The x-ray spectrum is found to have several humps which move to the higher energy side as the atomic number of the target increases. This atomic number dependence is explained by a semi-Moseley's law and allows us to predict a target material most suitable for generating the photons of desired energies. Conversion efficiencies of 1.5 rk, 3keV x-rays are obtained also as a function of laser wavelength at the intensity of 1013 W/cm2. The conversion efficiency of keV x rays has been enhanced by a factor of 2 % 3 with a controlled prepulse laser. From the semi-Moseley's law we find that cryogenic targets using either Xe or Kr in a liquid or solid phase may be most useful for a number of applications because they radiate 1 % 3 keV x rays efficiently and never deposit on the x-ray optical components and the objects to be exposed.
Laser Plasma Sources for Scanning X-Ray Microscopy
A. G. Michette, C.P. B. Hills, A. M. Rogoyski, et al.
Measurement of the soft X-ray intensity emitted from the plasma formed by focusing a 20 Hz, 500 mJ Nd:YAG laser beam onto solid targets indicate that a similar soft X-ray source employing a laser with a repetition rate of a few hundred Hz will be suitable for scanning X-ray microscopy. At particular X-ray energies, the brightness of such a source is comparable to that from synchrotron sources such as the (non-upgraded) SRS at Daresbury.
Soft X-Ray Stimulated Bremsstrahlung In Traveling Longitudinal Electric Wake-Fields Of Two-Beam Pill-Box Cavities
S. H. Kim, K. W. Chen, H. E. Wilhelm
The amplification of laser light in a free electron laser (FEL) due to stimulated bremsstrahlung in a traveling longitudinal undulating electric field is derived. It is shown that this FEL provides sufficient gain to be used as a coherent radiation source down to the soft x-ray regime. It is suggested that, among other possibilities, the wake-field produced in a two-beam elliptical or annular pill-box cavity is suitable for the required traveling longitudinal undulating electric field.
A Photoabsorption Experiment On Transient Laser Excited Low Z Ions In The Soft X-Rays
E. Jannitti, P. Nicolosi, G. Tondello, et al.
The technique of using two laser produced plasmas for absorption spectroscopy of ionic species has been greatly improved. A new signal detection system and a new data processing technique have been implemented in the experiment. This experimental technique has been applied to the absorption spectroscopy of transient moderately charged ions. The absorption spectra of the is electron of the Be IV, III, II, I ions with their relative photoionization spectra in the soft X-ray range are reported. Some preliminary results on the carbon ions are briefly discussed.
Threshold Estimations For Schafer's Photo-Ionization-Line Decay X-Ray Laser
Heinrich Hora
Schafer's PHILDEX-laser is a new scheme which consists in a cylinder-optical concentration of a short excimer laser pulse irradiating the high-Z coating of a cylindrical solid core of length £ and radius r. The pulse moves like a boots trap along the coating with nearly the speed of light. After 50% of the laser radiation is converted to X-radiation in the coating, this photo-ionizes preferentially the electrons in the lowest level of the core material. If nearly complete depletion with an atomic density n*(inverted states) is reached, the electrons at the energetically next higher level will decay to the lower level. For £» r, the preferential direction of the emitted superradiance along the axis will produce an X-ray laser pulse. For this laser some estimations are reported about the following properties: the line shift by recoil in the core which was assumed to be an instantly produced plasma where no Mossbauer-recoil is permitted. This is combined with the Doppler shift of the ionic motions. The overlapping of lines is found sufficient for the laser. An estimation of the necessary inversion density and the geometry of the medium are given. For the then necessary minimum core length of lmm, laser pulses in the order of 100 J are necessary with duration of less than 3 psec, preferably less.
A Small Gas Puff Z-Pinch X-Ray Source
P. Choi, A. E. Dangor, C. Deeney
The gas puff Z-pinch is an intense pulsed plasma X-ray source energized by a capacitor bank. Typically 5-10% of the electrical energy stored in the bank is converted into X-ray radiations with wavelengths less than 100 Å. Such devices have applications in X-ray microscopy, lithography, spectroscopy and X-ray optics engineering. Here we present the results of a parmetric study of the X-ray emission from a small gas puff Z-pinch which has 4kJ of stored electrical energy. The quantities measured are the soft X-ray emission in the wavelength range 4 to 85 A and the hard X-ray emission with wavelength less than 2.5 A. These quantities are found to depend on the gas used and the mass of gas imploded. Conditions exist that maximise the soft X-ray emission from the pinch. It is also shown that the hard X-ray emission can be reduced significantly by changing the anode material and by varying the mass of the gas imploded.
Laser Created X-Ray Sources For Microlithography
M. Chaker, H. Pepin, V. Bareau, et al.
Laser created X-ray sources have been investigated both theoretically and experimentally using λ = 1.06 μm and λ = 0.26 μm and short pulses (0.5 nsec). Some preliminary results are given with UV radiation obtained with a long pulse (25 nsec) excimer laser. The con-version efficiency of the X-ray emission in the sub-keV (0.1-0.75 keV) and keV (0.75-2 keV) ranges is given for various atomic numbers and a large range of laser intensities. Using these results and resist sensitivities, we discuss the characteristics of the laser required for X-ray lithography.
Two Wavelengths Imaging Of Laser Heated Thin Foils In The Soft X-Ray Range
R. Benattar, J. Godart
We present results of preheat of thin foils heated by laser at 0.26 μm. The emission of the rear of the thin foils is imaged with the use of two Schwartzchild microscopes at 80 eV and 40 eV. These microscopes made of multilayered mirrors have a large aperture (f/2.5) and a good spatial resolution (5 μm) for a total reflec-tivity of about 1 %. The time integrated two dimensional images and time resolved images are shown. From the records at these two wavelengths we are able to deduce the temperature of the rear of the foils and its spatial distribution inside the heated surface of the foils.
Design Considerations For Storage Rings For Synchrotron Radiation
Klaus Wille
Electron storage rings are the most effective sources of synchrotron radiation. The required extremely low beam emittance makes a very careful design of the beam optics necessary including the chromatic corrections. This adds nonlinear magnetic fields reducing the dynamic aperture for the beam. An example of low emittance optics is the modified Chasman-Green lattice of the ESRF. Synchrotron radiation with extremely high brilliance is produced by undulators and wigglers. These devices require special straight insertions.
X-Ray Measurements For The Determination Of Extension And Divergence Of Electron Beams In Storage Rings
F. Riehle, E. Tegeler, B. Wende
Methods are presented for the determination of the vertical extension and divergence of electron beams in storage rings which also allow to obtain the vertical emittance. The ver-tical extension of the electron beam of the storage ring BESSY was measured with an X-ray slit camera. The vertical divergence was derived from the vertical angular distribution of the synchrotron radiation of the storage ring measured with either an X-ray polarimeter or an energy dispersive X-ray photon counter.
Simple Method For The Determination Of The Characteristic Photon Energy E[sub]c[/sub] Of A Storage Ring By X-Ray Measurement At Photon Energies Around 20 E[sub]c[/sub].
F. Riehle, E. Tegeler
A spectroscopic method for the determination of the characteristic energy Ec of an electron storage ring is presented, which preferably can be used at VUV storage rings with Ec between 100 eV and some keV. With an energy dispersive photon counter (e.g. a Si(Li)-detector) the spectral photon flux of the synchrotron radiation around 20 E is measured with the intense low energy radiation cut off by filters. As the spectral photon flux at high energies strongly depends on Ec, the characteristic energy can be determined with a small uncertainty. For the electron storage ring BESSY Ec was determined with an uncertainty of 0.25 %. The result is in good agreement with the value of Ec determined from known electron energy W and magnetic induction B in the bending magnet.
Synchrotron Radiation Diagnostics At BESSY
F. P. Wolf, P. Kuske
Size, position and stability of the synchrotron radiation source BESSY are determined at present by imaging optical systems and wire monitors in the beamlines and by electrostatic position monitors in the storage ring. Since the size of the source has been brought down to FWHM-values Δy = 0.15 mm in vertical and Δx = 0.4 mm in horizontal directions for stored currents of IR = 200 mA, the requirements with respect to the stability of position and size have increased considerably. Vertical position changes of 0.1 mm lead to apparent energy shifts of up to 100 meV on monochromators without entrance slits. Even when entrance slits are used, the intensity and degree of polarization of the radiation depend on the stability of the position of the source. All monitors in the beam lines and the monochromators themselves are sensitive to thermal expansion of their optical components. This means, that slow shifts occur during the life time of one filling of the storage ring and sudden shifts during each injection (between closing and opening of the beam shutters). Apart from these long time effects, flaring of the image of the source in the frequency range of a few Hz becomes visible on the optical system from time to time. In order to separate ring problems from beam line problems, such monitor systems are indispensable. Improvement of the monitors and measurements with a random access camera will be presented and discussed.
Beamline for a Soft X-Ray Undulator at the Photon Factory
Hideki Maezawa, Masami Ando, Tetsuya Ishikawa, et al.
Present status of a beamline for a 60 period permanent magnet soft x-ray undulator inserted in the 2.5-GeV Photon Factory storage ring is described in detail. Two soft x-ray monochromators and a soft x-ray microscope installed in the beamline are also described. Design concepts of these instruments are presented and some remarks are made on their installations.
On-Axis Streak Camera Measurements Of Undulator Light On Beam Line V at SSRL
Roman Tatchyn, Art Toor, Hayrettin Kilic, et al.
Direct on-axis time resolved measurements of undulator light have been taken with an x-ray streak camera on Beam Line V at SSRL. A UHV chopper, especially designed for high undulator power levels, was used to provide gating signals for the streak camera sweeps. A description of the system, as well as the results of the measurements and their preliminary interpretation, are presented in this paper.
Micropole Undulators In Synchrotron Radiation Technology: Design And Construction Of A Submillimeter Period Prototype With A 3 Kilogauss Peak Field At SSRL
Roman Tatchyn, Paul Csonka
The availability of undulators with submillimeter periods will profoundly affect the future development of soft x-ray sources and their attendant instrumentation. Outputs comparable to those of present-day conventional undulators, obtainable with much lower energy storage rings, is only one promising aspect of such devices. This paper critically examines some of the future prospects of such devices and describes the design and practical construction of a 1" long prototype consisting of 35 periods. A proposed experiment to test this device on a linac is described.
Off-Axis Radial Properties Of Undulator Light
Roman Tatchyn, Ingolf Lindau
The off-axis angular harmonics of each spectral harmonic emitted by an undulator display a varying radial structure. In this paper we display such structures and provide a descriptive analysis For their maxima and minima.
Mirrors Of Soft X-Ray Beam Lines: General Considerations And Radiation Effects
Volker Salle
Some general considerations for the application of mirrors in soft x-ray beamlines are reviewed and examples for state of the art mirrors are presented. In view of future light sources special attention is paid to deformation and damage of mirrors exposed to synchrotron radiation beams with high power densities.
Fabrication of Imaging X-Ray Optics
R. C. Catura, E. G. Joki, W. J. Brookover
Our laboratory is involved in fabricating imaging x-ray optics for both astronomical and laboratory applications. A large Wolter type I x-ray telescope is being fabricated as part of an x-ray spectrometer for observing the spectra of cosmic sources in the wavelength range from 8 to 30Å. The mirrors for this telescope are fabricated from blanks of 5083 aluminum alloy that have been figured by diamond turning. These figured surfaces are polished by applying a thin coating of acrylic lacquer that is subsequently overcoated by vacuum deposition of approximately 400Å of tungsten. This telescope is the imaging element of an X-Ray Objective Grating Spectrometer (XOGS) that uses reflection gratings for spectral dispersion and an image sensitive proportional counter to detect the dispersed x-rays. The XOGS will be flown on an ARIES rocket in the summer of 1987 to observe the soft x-ray spectrum of Sco X-1. The present status of the telescope will be described and some data from a preliminary test of the spectrometer at the Marshall Space Flight Center X-ray Calibration facility will be presented.
Features Of Manufacturing And Qualification Tests Of A High-Resolution Wolter I Mirror System
Dieter Reinhardt
A 4nested mirror system of the Wolter I type has been developed in 3 steps. The optical qualification test was performed with a verification model (VM) for which a mirror pair was produced in the original size. For the mechanical and thermal qualification tests, the VM was extended into a structural thermal model (STM). The mirrors for the flight model (FM) and all mechanical structural elements have already been completed.
A High Resolution Coordinate Measuring Machine for the Testing of X-Ray-Mirrors
K. Becker, E. Heynacher
For the purpose of detecting tangent errors down to 0,1 arc sec on x-ray-mirrors, a computer controlled 3-axis coordinate measurement machine (CMM) has been developed which allows a position resolution of 10 nm in all coordinates. The concept of this CMM is based on the complete separation of machine controlling and measuring systems. Thus the measurements are not related the quality of machine axis but to the quality of reference mirrors which form normals for the three coordinate axes. Experiments performed until now show a reproducibility of better than 0,1 arc sec for linear measurements. Measurements of three dimensional structures are in preparation.
Contarination Layers on EUV Reflectors
Marion L. Scott, Paul N. Arendt, Bernard J. Cameron
We have utilized a visible in situ ellipsometer to investigate the growth of oxide surface layers on aluminum and silicon films deposited in an ultra high vacuum (UHV system. A single molecular layer of oxide f%rms on the aluminum film surface in 1 hour when exposed to a partial pressure of 2 x 10-8 Torr of either oxygen or water vapor. The single molecular oxide layer that forms in 4 hours on silicon when exposed to 2.5 x 10-8 Torr of oxygen is Si or, if the vacuum ion gauges are operating, but it appears to be SiO if these gauges are turned off during the layer formation. The time of formation of these layers is inversely proportional to pressure. The growth rate of the oxide surface layer drops dramatically after formation of this first morolayer on both aluminum and silicon. Other gases, such as methane and carbon monoxide were found to be essentially urreactive with the aluminum film.
Analytical Model For Determining Temperature Transients In Multilayer Thin Films With Uncooled And Cooled Soft X-Ray Optics
J. R. Palmer
This paper describes the temperature gradients in multilayer optical thin films when subjected to soft x-rays. Equations are described for use in evaluating the time-temperature history of each coating interface and subsequent energy distribution to the substrate. One and three dimensional equations are provided to examine the impact of thermal diffusivity, relaxation time, and subsequent temperature rise in the optical thin films. Coatings that are supported by cooled substrates are evaluated as a function of substrate material and cooling medium heat transfer coefficient. Coating temperatures and substrate temperatures are evaluated for conditions satisfying the semi-infinite plate model.
Analytical Model For Transient Strehl Ratio Distribution In Soft X-Ray Optical Systems
J. R. Palmer
This paper will describe a first order analytical technique for evaluating the Strehl ratio of a system composed of various optical components in a soft x-ray system. The basic elements of the model are to provide budgeting criteria that will permit the maximum energy in the central lobe of a far field distribution. Budgeting components will consist of figure error on the component, thermal distortion for transient and steady-state, pressure ripple for cooled substrates, and energy loss due to scatter and absorption in the coatings and the substrate.
Steering Mirrors For The Soft X-Ray Range
A. V. Vinogradov, V. M. Elison, V. I. Zilina, et al.
Concave glancing incidence mirrors for deflection and turning of soft X-ray beams by large angles are considered. For carbon-coated superpolished concave mirror the reflectivity of 60% is measured for 6.76 rim radiation and turning angle T = 29°, which is two orders higher than for beam deflection by the same angle with one Fresnel reflection from a plane carbon mirror.
Grazing Incidence Telescopes For Satellite Borne UV And X-Ray Astronomy Missions Including ROSAT, XMM and Lyman
Bernd Aschenbach
Grazing incidence telescopes have been in use for quite some time for X-ray applications. High resolution Wolter type I telescopes have been flown on board of Skylab, the Einstein and the EXOSAT satellites. ROSAT will he the next space borne observatory, which will perform for the first time a complete sky survey by means of a large high resolution grazing incidence X-ray telescope. The design and fabrication of the mirror assembly are presented including metrology measurements and full aperture X-ray tests. The X-ray image of the fully assembled prototype model shows a measured radius of 2.0 arcsec and 3.2 arcsec for the 50 (7.') and 80 encircled energy, respectively. Metrology measurements of the not yet assembled flight mirrors indicate an even better performance including microroughness of 2.6 Å rms. A cluster of highly nested Wolter type I telescopes has been proposed for ESA's future X-ray astronomy cornerstone mission XIM. The optical design of the mirror assembly optimized to high throughput but moderate re-solution is presented. Although originally proposed for X-rays grazing incidence telescopes start to be preferred for use at longer wavelengths due to the lack of high reflectivity coatings throughout the region from the X-rays to the UV at '- 1000 Å. The future UV astronomy mission Lyman selected for an industrial Phase-A study by ESA utilizes a Wolter. Schwarzschild type II telescope which feeds a high resolution (λ/Δλ = 30.000) spectrograph covering the 900 - 1200 Å region. The optical design of the telescope is described and the error budget for the manufacturing of the 1 arcsec telescope is discussed.
X-Ray Spectrometer For ROSAT II (SPECTROSAT)
Peter Predehl, Heinrich Brauninger
The objective transmission grating was one of the earliest inventions in the field of X-ray astronomy and has been incorporated into Skylab, HERO-P, and EXOTAT. In recent years there have been advances in grating technology and spectrometer design. A high precision mechanical ruling and replication process for manufacturing large self-supporting transmission gratings has been developed by an industrial manufacturer in cooperation with the Max-Planck-Institute (MPI). Theoretical analyses have determined the optimum configuration of the grating facets and the grating surface in order to correct third order aberations and obtain maximum resolving power. We have verified experimentally that the predicted efficiencies may be achieved. In addition, an experimental study of large grating assemblies for space telescopes was made in industry with scientific guidance by MPI. Main objectives of this study were the determination of mechanical loads during launch, as well as the design, construction and fabrication of a representative model of a ROSAT grating ring. Performancy studies including instrument pro-perties as well as the simulated radiation from hot plasmas have shown the ability of SPECTROSAT to perform high efficiency, high resolution line-spectroscopy on a wide variety of cosmic X-ray sources.
ROSAT Experience On X-Ray Optics Contamination
Hans Hartmann, Roland Nord, Helmut Schwille, et al.
The different contamination control measures and monitors for the X-ray satellite ROSAT are described. Results are shown for cleanliness monitoring on ground and in vacuum test by Quartz Crystal Microbalance (QCM) and by analysis of witness mirror samples with Secondary Ion Mass Spectrometry (SIMS) and X-ray reflection measurements. Some unexpected contamination effects have had considerable impacts onto contamination control measures, especially onto specification of contamination witness samples, and they requested intense efforts with respect to contamination analysis. These investigations showed that there are considerable impurities of hydrocarbons trapped within the evaporated gold layers, caused by residual hydrocarbons in the evaporation facility or resulting from an unusually high affinity to hydrocarbon contamination compared to bulk gold. The latter may be stimulated by structural properties of the evaporated gold layer.
Effects Of Mirror Contamination Observed In The ROSAT Programme
W. Burkert, B. Aschenbach, H. Brauninger
The high throughput of the ROSAT X-ray telescope is largely dependent on the reflectance of the gold coating of the mirrors in the wavelength region 6 - 100 Å. In this context measurements of the reflectivity and scattering of soft X-rays at various wavelengths and reflection angles have been performed on a large variety of flat mirror samples. The effects related to coating technique and surface contamination are discussed.
Surface Evaluation Of The Grazing Incidence Mirrors For The Extreme Ultraviolet Explorer
James Green, David S. Finley, Stuart Bowyer, et al.
The Space Astrophysics Group at the University of California, Berkeley, is currently producing four grazing incidence mirrors for the Extreme Ultraviolet Explorer. In conjunction with this effort, we are developing improved methods for the evaluation of these mirrors' performance. Imaging and reflectivity analyses at optical and extreme ultraviolet (EUV) wavelengths allow us to quantify a mirror's performance with regard to effective area, surface roughness, and image blur. We present here the results from our most recent EUV measurements, and our latest techniques for evaluating the surface microroughness.
The Performance Of The ROSAT WFC Mirrors
R. Willingale, S. R. Milward, M. R. Sims
The Wide Field Camera (WFC) to be flown on the German satellite ROSAT is an XUV telescope operating in the energy band 12-250 eV utilising Wolter-Schwarzschild Type I grazing incidence optics. The design and performance testing of the mirror system are reported. In particular extensive reflectivity measurements made in the range 12-250 eV are compared with theoretical predictions and X-ray scattering measurements are used to assess the quality of the reflecting surfaces. Details of the testing and calibration of the combined mirror and detector telescope system are given showing that the performance is as expected from mechanical and optical metrology and that the telescope performance is within specification.
The Crystal Monochromator at BESSY
J. Feldhaus, F. Schafers, W. Peatman
The crystal monochromator at BESSY covers the soft x-ray region above 800 eV up to about 5000 eV employing the (n,-n) double crystal arrangement with constant beam offset. Beamline and monochromator have been optimized for high flux and high resolution, and care has been taken to minimize radiation damage and temperature effects on the first crystal. The mono-chromator uses a novel mechanical linkage system for two simultaneous rotations and a translation and combines an effective homogeneous cooling of the first crystal with a simple in situ crystal exchange. Design features and performance data are presented.
Some Considerations On Glitches And The Design Of A Double Crystal Monochromator With Bent Crystals
P. van Zuylen, M. J. van der Hoek
Unwanted reflections, which are due to the structure of the crystal, cause glitches in the X-ray transmission of high resolution crystal monochromators. The wavelength at which the glitches appear depends on the orientation of the crystal. We show that by a slight rotation of the crystal in the plane facing the X-ray beam it is possible to cover a large energy range (5 to 14 keV) for EXAFS or XANES experiments with one set of crystals. The implementation in practice will be discussed.
Application Of A Simple Rotational Spherical Grating Mounting To High Resolution Soft X-Ray Spectroscopy
H. A. Padmore
The design of a new class of grazing incidence monochromator system is presented. The design uses a spherical grating in a simple rotation mounting with the non-dispersive focusing being accomplished with a separate focusing mirror. The characteristics of several configurations of the basic design are presented and the overall design procedures are discussed. The design is essentially free of aberrations and the principal degradation in resolution will be caused by tangential slope errors in the diffraction grating. The effect of the slope error on resolution is examined in detail. The design of an entrance slitless monochromator currently under construction at Daresbury is discussed.
Plane Grating Monochromators: The Working Curve Concept as Implemented in the SX-700
H. Petersen
We present a concept which describes the operation of BESSY plane grating monochromators in the two important modes: highest possible spectral resolution and alternatively very high spectral purity.
Spectroscopic Ellipsometry with Synchrotron Radiation: Latest Developments
J. Barth, R. L. Johnson, S. Logothetidis, et al.
This paper describes a project to perform spectroscopic ellipsometry in the VUV and soft x-ray spectral range using synchrotron radiation.
A Polarimeter for Soft X-Rays
A. Gaupp, W. Peatman
Exploiting polarisation effects significantly adds to the information obtainable from spectroscopy. Espe-cially circular polarisation is needed in a large class of experiments including but not limited to angular and spin resolved photo electron spectroscopy, investigation of circular dichroism in chiral molecules, and magneto-optical effects. Many of those experiments have been limited to photon energies below about 9 eV due to the unavailability of quarter wave plates /1/. At higher energies with suitable lasers the range has been extended up to 15 eV /2/. Using the natural polarisation properties of out of plane synchrotron radiation, the region up to 35 eV photon energy is accessable /3/.
Application of Spherical Gratings in Synchrotron Radiation Spectroscopy
H. Hogrefe, M. R. Howells, E. Hoyer
The recent development in grazing incidence grating monochromator design is discussed and the performance limiting factors for such instruments are examined. Especially the aberrations of toroidal and spherical gratings are investigated using the optical path function concept. It is shown that large radius spherical gratings, which can be produced with better slope tolerances than aspherics, also yield smaller overall line curvature than toroids. Therefore, a new simple spherical grating monochromator design is proposed and its performance is analyzed.
Studies of interfacial structure in WC multilayers
Ashley Fuller, Roman Tatchyn, Paul Csonka, et al.
This paper reports on a set of interfacial structure studies in WC multilayers. Statistical investigations were conducted to ascertain whether building up layers containing, on the average, an integer number of atoms could in any way minimize the effects of interfacial roughness.
Present Status of X-Ray Optics Research
D. Rudolph
A review of optical systems for soft x-radiation 0.5 nm ≤ λ ≤ 4.5 nm is given. Grazing incidence and multilayer mirrors are shortly discussed. Zone plate fabrication methods and accuracy requirements are discussed and some aspects of holographic zone plate fabrication are described.
X-UV Optics in near-normal incidence realised at the "Institut d'Optique"
J. P. Chauvineau, J. P. Marioge, F. Bridou, et al.
Two objectives to be used at 304 Å, in near-normal incidence have been made at IOTA : one is Ritchey-Chretien Telescope, the other is a Schwarzschild microscope used to observe laser heated targets. They are both made from two spherical surfaces shaped with an accuracy of λ/10, and covered by Si/Re-Wmultilayers. For the Ritchey- Chretien, the surfaces were aspherized by vacuum deposition before coating. Multilayer period and interface roughness were evaluated by using X-ray reflectanetry during the deposition process and grazing incidence X-ray reflectometry after the multilayer coating. A 7 A rms roughness for Si, 10 AÅ for W-Re, and a reflectivity of 10% were evaluated for each telescope mirror. For minimazing aberrations, the two mirrors of the Schwarzschild microscope were very accurateley centered. Results shows a resolution better than 4 gm for this instrument at the 304 Å wavelenght used.
Use Of X-Uv Multilayered Optics For Synchrotron Radiation, Plasma Diagnostics And Astrophysical Research.
P. Dhez
X-UV multilayer mirrors have now been made and tested for about ten years , so it is the time to look if the initial hopes have been satisfied. These new mirrors have found applications in X-UV optical systems as Bragg reflectors alone, or combined with the grazing incidence mirrors and gratings. In this review paper we shall consider mainly the astrophysics, plasma physics and synchrotron radiation applications, the three fields for which the X-UV is an important range, to illustrate some kinds of problems which have been solved by using X-UV multilayered mirrors. Finally we shall try to indicate new promising directions.
Absolute Reflectivity Measurements Of Multilayer Mirrors In The Soft X-Ray Region
K. B. Youn, C. Sella, R. Barchewitz, et al.
Multilayer soft X-ray mirrors were deposited by using a triode dc sputtering system, equipped with an accurate method pf film thickness monitoring which enables the thickness to be controlled with an accuracy of better than 0.1 Å. Absolute reflectivity measurements of Ni-C and W-C multilayers at λ = 44.79 Å (c lea) in the first and second order Bragg Peaks, and at λ = 67.8 Å (B Ka) only in the first order were carried out. The incident beam is previously polarized by two parallel plane multilayer mirrors fixed at an angle close to Brewster's one ( 0 = 45°). Thus the measured reflectivitie are not affected by a progressive variation of the P component. The preliminary results obtained at λ = 113 Å (BeKot) are also presented.
Multilayer Theory Of X-Ray Reflection
P. G. Harper, S. K. Ramchurn
A new basis is presented for the calculation of reflection coefficients of x-rays by multilayer artifacts. Thin film interference is treated at atomic plane level, using an iterative 2 x 2 matrix method. Analytic and computational comparisons are made with the conventional dielectric approach for TM and TE polarisations at non-normal incidence. Good agreement is obtained with recent accurate measurements by Evans.
Measurements Of Diffraction Properties Of Selected Multilayers Using A Triple-Axis Perfect Crystal X-Ray Diffractometer
Allan Hornstrup, Finn E. Christensen, Herbert W. Schnopper
We present measurements of diffraction peaks from six different multilayers of W/Si, Ni/C and ReW/C-layering. We have used FeKa-radiation and a three-axis, perfect crystal, x-ray diffractometer. The measurements suggest that these multilayers do not suffer seriously from imperfections. Improper estimates of the relative layer thickness of the two components may be as important as imperfections for these multilayers. All the multilayers studied show mosaicity which would be expected to originate in the substrate.
Normal Incidence X-UV Mirrors
Charles M. Falco, Felix E. Fernandez, P. Dhez, et al.
We describe the fabrication procedure as well as results of an extensive series of characterization measurements, model-fitting and synchrotron tests on Si/W multilayers designed as normal-incidence reflectors for -200 Å radiation. Characterization techniques used were low-angle diffraction, Bragg-Brentano and Seemann-Bohlin diffraction, Read camera, transmission electron microscopy and Rutherford backscattering spectroscopy. To our knowledge, this is the first time such a comprehensive set of characterization techniques has been applied to a multilayer x-ray mirror. Reflectances for -200 Å calculated using the results from these various characterization techniques are found to agree very well with measurements obtained with synchrotron radiation.
Studies Of Multilayers As Monochromating Elements In The Region 200 - 900 eV Using Synchrotron Radiation
G. van der Laan, M. P. Bruijn, J. B. Goedkoop, et al.
In the energy region between 400 and 900 eV the performance of monochromators based on both gratings and inorganic crystals is poor with respect to that in other regions, so that there has been speculation on the role that multilayers can play. We report results of characterization of a double "crystal" monochromator for synchrotron radiation in the region of 200 - 900 eV in which two Ni/C multilayer coatings (2d = 62 Å) are used. The energy resolution is measured to be about 75 by reflection measurements with a KAP crystal and by recording absorption edges and "white lines" of 3d transition metals. The potential of multilayer coatings is further illustrated by measurements of reflection profiles of other ReW/C coatings. We also report results on a second approach in which a double "crystal" monochromator is equipped with an organic crystal (KAP) preceded by a single multilayer with a layer thickness matched to the 2d-spacing of the organic crystal. This arrangement is shown to protect effectively the organic crystal from radiation damage and to give an energy resolution of about 1000, although the reflectivity is low. The use of multilayers in other concepts to mono-chromate synchrotron radiation is also discussed.
Soft X-ray Platinum-Carbon Multilayer Mirrors
Brian L. Evans, Barry J. Kent
5 cm diameter, plane multilayer mirrors of different 2d value, have been fabricated from polycrystalline platinum and amorphous carbon. The performance of these multilayers as a function of layer number and thickness is presented. The importance of the commensurate nature of the stack in determining the Bragg reflectivity values (typically greater than 40% at wavelength 0.834nm) is described with reference to TEM photographs and resistivity measurements.
Focusing Of Undulator Light At Spear with A Lacquer-Coated Mirror To Power Densities Of 10[sup]9[/sup] watts/cm[sup]2[/sup]
Roman Tatchyn, Paul Csonka, Hayrettin Kilic, et al.
A lacquer-coated, diamond turned Cu ellipsoid has been used to micro-focus undulator light from Beam Line V at SPEAR down to a half-power diameter of about 13 microns. This spot was source-size limited, as has been demonstrated with ray tracings of the optical system. The symmetry of the image, as well as its size and power density, clearly make this optic ideal for many soft x-ray applications, in particular for x-ray microscopy, microprobes, and for pumping soft x-ray transitions in various media.
Multilayered Foils As Radiation Entrance Windows And Spectral Filters For Image Converters In The Ultrasoft X-Ray Wavelength Region
K. H. Stephan, H. Brauninger, H. Kaase, et al.
We have been developing ultrathin multilayered films to serve as radiation entrance windows and spectral filters in satellite borne position sensitive proportional counters for imaging ultrasoft X-rays from celestial sources in the wavelength region 0.6 < X < 10 nm. The performance data being measured will be given.
Performances Of C-W Multilayers As Soft X-Rays Optics : High Reflectivity In The Range 2d = 60 to 100 A
Ph . Houdy, V. Bodart, C. Hily, et al.
Diode RF sputtering technique has been used to produce carbon-tungsten ultra thin layers stacks for application in the soft X-ray domain as optical system. In situ kinetic ellipsometry has been chosen to control the multilayers growth with a great accuracy. Grazing X-ray reflection (1.54 P., absolute soft X-ray reflectivity (44.7 Å) and cross section transmission electron microscopy results confirm a posteriori the ellipsometry ones. Deposition conditions have been optimized using these characterizations. The thick-ness fluctuations are very low (0.2 % per layer). We have observed the smoothing of the layers roughness as the number of C-W sequences increases (the substrate having a roughness of 7 Å, the layers of 2 Å). We have realized multilayers in the range 2d = 60 Å and 2d = 90 Å. Their reflectivities typically reach 8 % = 45° at 44.7 Å) for the first ones and 13 % (9- = 30° at 44.7 Å) for the second ones. We have also realized stacks with a great number of layers in the range 2d = 100 A. 17 % reflectivities have been reached for a 180 layers stack.
Use Of Self-Scanned Photodiode Array For X-Ray Multilayer Characterization
J. Corno, E. Dartyge, P. Dhez, et al.
To reach the theoretical performance of the new generation of artificial X-ray and X-UV Bragg reflectors, it is necessary to improve the layering qualities of the various deposition methods and the accuracy of measurements of the parameters of the produced stack. Such layered structures are not exclusively X-rays optics oriented: microelectronic and optoelectronic devices rely on superlattices structures. Such layered structures, both crystalline and amorphous, are now investigated in other fields of physics because their quasi bidimensional structures give rise to new possibilities in such field as magnetism and superconductivity .
A Software Package For The Analysis Of General Multilayer Performance Data
Bryan G. Peterson, Hans K. Pew, Larry V. Knight, et al.
In an effort to make data on the reflectivity and transmission of multilayer optical elements more usable, we have developed a computer code for the manipulation and graphical display of a general data set consisting of x, y, and delta-y values. The code was developed for a DEC VAX computer running a version 4.2 or later VMS operating system. Facilities are available for algebraic manipulation, editing, smoothing, interpolating, and deconvolving data sets in a straightforward way. The code is entirely self-contained with the exception of the graphics output support, which is centralized to allow for simple interfacing to the graphics package resident on the target system. The capabilities of the code are described and sample output is shown.
Study Of Multilayers Subjected To Intense Radiation
L. V. Knight, K. J. Gray, B. G. Peterson, et al.
Many promising applications of multilayer x-ray optical elements subject them to intense radiation. In this paper we present simulations of multilayer performance under extreme heat loads and preliminary results of robust multilayer characterization experiments.
King's College London/SERC Daresbury Scanning X-ray Microscope
R. E. Burge, M. T. Browne, C. J. Buckley, et al.
The present status of the soft X-ray microscope is described and a short description is given, with likely development paths for the future, of the Daresbury synchrotron source, the monochromator, the high-resolution zone-plates, the scanning specimen stage, image recording and methods of image enhancement. It is considered that the instrumental developments needed for images at 10 nm resolution will take a further two or three years.
The Gottingen Scanning X-ray Microscope
B. Niemann
The Gottingen scanning X-ray microscope was tested at the BESSY storage ring. Images with 0.1 micrometer resolution were obtained with 4.5 nanometer radiation delivered from the BESSY bending magnet. The number of spatial coherent photons in 1% bandwidth, which can be delivered by the used zone plate linear monochromator, was calculated to be 1.7 x 10 E 8 photons per second during this tests. The scanning time was less than 10 milliseconds per image point at a measured photon rate of more than 10 E 6 per second. The scanning time for one image was about 3 minutes.
Possibility of Spatially Resolved Synchrotron Radiation Spectroscopies Using a Stigmatically Focussing Monochromator
H. Petersen, W. Braun, E. E. Koch, et al.
At BESSY a beamline for applications in laterally resolved photoelectron-spectroscopy is planned. The performance of such a small spot scanning ESCA line (ESCAN) using synchrotron radiation is described. In the present design a combination of a stigmatically focussing SX-700 type plane grating monochromator and a zone plate create a microspot of less than 5 μm in diameter. The flux concentrated in that spot should make small spot ESCA possible even with synchrotron radiation from dipole magnets.
Preliminary Optical Design Of An Imaging Soft X-Ray Microscopy (IXM) Beam Line And Fabrication Of Zone Plates In Hefei
Yong-Gang Su, Shao-Jun Fu, Yun-Wu Zhang, et al.
A design of an optical system for testing zone plates by imaging with soft x-ray microscope is presented. The progress of zone plates fabrication in Hefei is also described. Finally, some aspects of our future plan are mentioned too.
Soft X-Ray Diffraction Of Striated Muscle
Fan S. F., Yun W. B., Rosser R. J., et al.
Diffraction patterns of striated muscle were obtained with x-ray wavelengths from 2.5 to 3.5 nm. The experimental method is described and the advantage of using soft x-rays for muscle study is discussed.
Fabrication Of X-Ray Optical Elements By Electron Beam Lithography
Hiroaki Aritome, Susumu Namba
Electron beam lithography is an efficent method for fabricating x-ray zone plates. In this report, fabrication of x-ray zone plates by electron beam lithography whose applications are for an x-ray microscope and an x-ray linear monochromator at the undulator radiation line (fundamental wavelengths:1.3-3.0 nm) of the Photon Factory in Tsukuba. Experiments using synchrotron radiation to characterize fabricated zone plates are described. It is also shown that it is feasible to fabricate x-ray zone plates with spatial resolution of 20 nm by electron beam lithography.
Electron beam lithography and nanometer structures-fabrication of microzone plates
V. Bogli, P. Unger, H. Beneking
With the aid of a 100 keV electron beam lithography system, microzone plates have been fabricated. The system has been designed for generating structures with lateral dimensions in the below 100 nm range. The particular demands on high resolution, high efficiency imaging Fresnel zone plates and the arising problems concerning lithography and pattern transfer are discussed. We will show a step by step improvement of fabricated microzone plates with an outermost zone width of 50 nm. A thin titanium intermediate layer is used as a stable mask to generate ion milled gold absorber rings with very steep walls. The zone plates have been tested by imaging one another in an X-ray microscope, and compared to the image obtained with the holographically fabricated MZP3 microzone plate from Gottingen (Schmahl et al., /1/).
Zone Plate Manufacture at King's College London: Current Status and Future Plans
R. E. Burge, A. G. Michette, M. T. Browne, et al.
The current status of the soft X-ray zone plate programme at King's College is discussed, and some preliminary ideas for the future enhancement of the programme are considered.
Phase Zone Plates As Condensers For The Gottingen Scanning X-Ray Microscope
Roland Hilkenbach, Jurgen Thieme
With the Gottingen scanning x-ray microscope the synchrotron source is imaged by x-ray optics into a monochromatic small scan spot, through which a specimen can be moved. Hereby one part of the optics, the condenser zone plate and a pinhole, works as a linear monochro-mator in the wavelength region of λ= 2.36 nm to λ= 4.5 nm. The efficiency of such a condenser should be as high as possible to minimize the loss of radiation. Phase zone plates have a four times higher efficiency in the first order of diffraction than amplitude zone plates. Two condenser zone plates, KZP4 and KZP5, have been constructed so that they are well suited for the use in the scanning microscope. These zone plates have been made holo-graphically by superposing two wavefronts of laser light in an specific designed optical arrangement and exposing the zone plate structure into a photoresist. Using reactive ion etching (RIE) the structure has been transformed into Germanium. The thickness of the zone plate has been chosen to show at λ = 2.36 nm a phase effect. The efficiency has been measured at the Berliner Elektronenspeicherring Gesellschaft fUr Synchrotronstrahlung m.b.H., Berlin.
Soft X-ray Radiometry
M. Kuhne
For soft X-ray radiometry source and detector standards are required. The electron storage ring can serve as a primary source standard with an uncertainty in spectral radiant power of 2 %. Transfer source standards are being developed with uncertainties of 10 to 15 %. Ionization chamber, proportional counter and Si(Li)-detector can with limitations serve as primary detector standards. Radiant power determination with uncertainties of 3 to 6 % are achievable. Calibrated Al203 diodes are available as transfer detector standards for wavelengths > 5 nm with a calibration uncertainty of 10 %.
Characteristics And Applications Of Semiconductor Photodiodes From The Visible To The X-Ray Region
J. Barth, E. Tegeler, M. Krisch, et al.
The quantum efficiencies of a Si pnn+ and a GaAsP Schottky photodiode have been measured in the photon energy range from 5 to 1000 eV. The efficiency is generally much higher than that of photoemissive detectors. The performance of the Si diode is affected by soft X-ray exposure, but for the Schottky diode a stable quantum efficiency is observed over the entire spectral range making this device attractive for many applications.
Spectral Efficiency and Resolution of Si(Li)-Detectors for Photon Energies between 0.3 keV and 5 keV
F. Riehle, E. Tegeler, B. Wende
The spectral efficiencies of energy dispersive Si(Li) photon counters have been measured using the storage ring BESSY as a radiometric standard source of extremely low photon flux of the order of 1 photon/(s eV). The detectors were irradiated with white synchrotron radia-tion when the storage ring was operated with only about 5 electrons stored. For energy calibration and measurement of the energy resolution X-ray emission lines excited by a 55-Fe source were used. Towards lower photon energies the efficiency is drastically decreased by the building-up of an ice-layer on the permanently cooled detector. By this surface contamination also the energy resolution of the detector is affected. The performance of detector can be recovered by a warming-up procedure.
Detective Quantum Efficiency Of Film Emulsions
Lotti Jochum
Photographic films are used as detectors in x-ray microscopes. A criterion for the sensitivity of film emulsions to soft x-ray radiation is the detective quantum efficiency (DQE). To keep the radiation dose transfered to the observed object as small as possible, one is interested in emulsions with a high DQE. Measurements have shown, that Ilford nuclear research emulsions have a much higher DQE than conventional films. A methode to determine the DQE of film emulsions and the results of the measurements will be described in detail.
Examinations Of Detector Systems For High Photon Rates In The Ultrasoft X-Ray Region
Peter Guttmann
For biological and medical examinations ultrasoft x-rays in the wavelength range of 2.3 nm up to 4.5 nm are well suited. To get good images of objects with low contrast such as biological specimens a high signal to noise ratio is, required. As example in a scanning x-ray microscope high photon rates with more than 10° photons/s in the scanning spot are needed. The radiation dose of the specimens should be as small as possible. For that reason the Gottingen scanning x-ray microscope working at BESSY is best suited. To use for the image formation as much photons as possible it is necessary to build up a detector system with a high detective quantum efficiency (DQE) and with the possibility to process high photon rates. In form of a short review the advantages and disadvantages of detector systems for ultrasoft x-rays are described. Detailled examinations of a photon counting detector system with a proportional counter are described. Results of detector systems with two different diodes - one passivated ion-implanted silicon junction diode and one GaAsP-Schottky diode are given. New results with an integrating GaAsP-Schottky diode detector system will be presented.
Soft X-Ray Fluorescence (UFIV Compatible) Proportional Counters for NEXAFS and SEXAFS Above the C,N,O, and S K Edges
D. A. Fischer, J. L. Gland
We describe the first ultra-high-vacuum-compatible soft x-ray detector for fluorescence yield (FY) detection of the near edge (NEXAFS) and extended (EXAFS) x-ray absorption fine structures above the C,N,O, and S K edges. This soft x-ray proportional counter is shown to offer more than a factor of twenty increase in surface sensitivity for chemisorbed sub-monolayer (ML) coverage with comparable signal-to-noise as compared with any conventional electron yield detector. The FY detector allows one to record SEXAFS spectra for =5/100 ML for both sulfur and carbon. The high sensitivity of the FY technique is due to the small amount of elastically and inelastically scattered background from the sample. In addition, the characteristic fluorescence radiation from the bulk or other contaminants can easily be eliminated using standard pulse height analysis techniques. Recently, experiments were performed at the NSLS VUV storage ring demonstrating that carbon edge FY NEXAFS measure-ments can be performed under 1 Torr of hydrogen gas. These prototype experiments coupled a soft x-ray proportional counter, reaction cell, and suitable soft x-ray entrance window to form a system allowing the experimenter to bridge the gap between UHV surface science and real reaction conditions encountered in catalysis.
Sensitization of CCD TV sensors for X-rays
Rudolf K. F. Germer
A high resolution X-ray tv-camera has been developed with CCD-circuits which were covered on the surface with a rare-earth converter screen. The resolution is 25 1p/mm, single photons can be detected for energies >10 keV and the quantum efficiency is 50% at 20 keV. The dynamic range is increased compared with uncovered CCDs. The qualities of CCDs are discussed for sensors with and without conversion layers.
Soft X-Ray Imaging using CCD Sensors
Werner Meyer-Ilse
An imaging CCD (charge coupled device) camera system for soft x-ray detection has been constructed. A reasonable efficiency is achieved down to photon energies of 270 eV. The performance of a system applying a CCD is compared with other detection techniques, and the different ways to increase the performance of x-ray imaging with CCD's are discussed.
The Focal Plane Instrumentation Of The ROSAT Telescope
E. Pfeffermann, U. G. Briel, H. Hippmann, et al.
The ROSAT telescope is equipped with two different kinds of X-ray image converters: two redundant position sensitive proportional counters (PSPC) and one high resolution imager (HRI), based on microchannel plates. The detectors and part of their front-end electronics as well as the gas supply system for the PSPC's are mounted onto a carrousel, which allows positioning of the desired imager in the focus of the telescope. All instruments, electronics, mechanisms, etc. are accommodated in the focal plane housing, which is mounted to the optical bench of the mirror system. We will give an overview of the focal plane instrumentation and present the performance of the X-ray image converters.
High Resolution Imaging Detector For Use With A Soft X-Ray Telescope
Leon Golub, Kenneth Kalata
For the past decade our group at the Center for Astrophysics has been involved in advanced x-ray imaging and data analysis for studies of the Solar corona. This effort has led in the past to our successes with grazing incidence optics, culminating in the very productive Skylab missions and related rocket programs. We are currently constructing a more advanced, extremely high-resolution telescope utilizing multilayer coated optics for imaging in the soft x-ray regime. This technique has the ability to achieve good x-ray reflectivities at normal incidence; thus very high quality imaging, possibly down to the diffraction,limit can be achieved. At the same time, the multilayer coating technique is inherently capable of moderate spectral resolution of order λ/δλ - 50-200. Because of the requirements which must be met in an imaging detector for Solar applications - small pixel size, large detector area and ability to handle high count rates - the photographic emulsion has so far been the best available choice. Film has many limitations for space instrumentation, the most important of which for our purposes are that it needs to be retrieved and that it has low detective quantum efficiency. Thus, we have begun develop-ment of a high efficiency electronic detector system which appears able to meet all of the stringent requirements of coronal studies. We presently have in our lab a working system with many of the required features and plan to direct the future development effort toward smaller pixel size and larger detector area. Our immediate goal is to construct a 2048 x 2048 system with pixel size of 5 p, capable of handling count rates up to a few x 105 cts s in the photon counting mode, and substantially higher rates in the A/D mode. In the following we will discuss the present status of the development program and show some of our results.