For the upgrade in 1998, the Fermilab D-Zero collaboration will install detectors which have many thousand scintillating and wavelength shifting fibers coupled to clear lightguide fibers. Our objective was to study whether the fibers' performance will deteriorate with age. Aging in these three kinds of fibers were studied by measuring attenuation lengths and light yields as a function of time. Attenuation lengths of scintillating and wavelength shifting fibers were measured using an ultraviolet light source and effective light yields of scintillating fibers were measured using a ²⁰⁷Bi radiation source. For clear fibers, attenuation measurements were made using light from a green light-emitting diode. Scintillating fibers have shown no noticeable changes in attenuation lengths and light yields over periods of up to 3.5 years when they were stored properly. Wavelength shifting fibers have been studied for a period of five months and have shown no degradation. Clear fibers have been studied over periods of up to seven months and have shown a reduction of a few percent in the attenuation length. These will have to be monitored for a longer period of time to establish if the effect is significant. The effects of aging on mechanically stressed fibers have also been studied. Light transmissions in clear fibers coiled into loops of various radii have been compared to transmissions in straight fibers. The stressed fibers have shown no change in the light loss for almost one year. The observations made over the past 3.5 years indicate that fiber aging is not a serious problem, however, the clear fibers require further investigation.

A tracking detector using 2.5-m-long scintillating fibers is being developed for the D-Zero collaboration at Fermilab. The scintillating fibers will be coupled to 11-m-long clear fibers that will transport light to the photodetectors. We have developed connectors which couple the two types of fibers. The first 128-channel prototypes were machined using Delrin plastic to have v-shaped grooves that position fibers in the connector. Fibers were glued into the grooves and their ends were finished with diamond fly-cut tools. Mating connectors were optically coupled by General Electric optical grease. Using a green light-emitting diode and a silicon photodiode, we measured average light transmission between 97% and 99%. The transmissions were monitored for a period of nine months and were found to be stable over that period. We investigated two arrangements; one where the clear fiber was slightly larger than the scintillating fiber and the other where both were the same size. We found the percentages transmitted essentially the same in both cases. The later arrangement, however, would make the detector simpler to fabricate. We are also actively searching for a nonfluid optical couplant which will remain stable for many years during the expected life of the detector. Recently versions of the v-groove connectors were made of acrylonitrile-butadiene- styrene plastic by injection molding and were found, in the case of coupling equal diameter fibers, to have light transmissions between 94% and 96%.

The D0 collaboration is upgrading its existing detector to provide enhanced functionality for physics is the Fermilab Main Injector Era, when the luminosity of the Tevatron Collider will evolve to levels in excess of 10³² cm^-2 sec^-1 in combination with reduction of the beam crossing interval to 132 nsec. The D0 upgrade retains the strengths of the existing detector which include hermetic coverage in fine-grained liquid argon calorimetry and muom detection using magnetized iron toroids and combines there with a new magnetic central tracking system based upon scintillating fiber and silicon strip technologies in a 2 Tesla solenoidal field. This paper summarizes briefly the elements of the upgrade and the central fiber tracker and presents recent measurements of performance of fiber tracking technology using the cosmic ray test facility at Fermilab.

An essential component of the CERN WA95/CHORUS experiment is a scintillating fiber tracker system made up of more than one million scintillating fibers, for the precise track reconstruction of particles. The design and construction of the tracker system as well as its opto-electronics readout are discussed. Performances of the detector are presented.

Chiral asymmetry is apparent in almost all living organisms on earth. However, the origins of chirality are unknown. One proposed theory of chiral asymmetry is by a symmetry-breaking transition such as the explosion of a supernova emitting neutrinos into the earth's biosphere during the prebiotic era. The discovery of weak neutral currents reinforces this theory. We present a simulation of this thoery by an electrical circuit that models the bifurcation equation of the chiral symmetry breaking process. There are three components that constitute this circuit: chiral circuit, sawtooth wave generator, and noise generator. The solution to the chiral circuit, which is the core of the hardware, generates the bifurcation equation. The sawtooth wave generator controls the bifurcation point (critical point), and the noise generator gives the system randomness. We included an adjustable bias voltage and saw a tendency to favor one symmetry over another (D or L) with randomness generated by noise.

We abstract developed a new technique that allows the trajectories of ionizing particles to be imaged with very high spatial and temporal resolution. This technique, developed for future experiments in high-energy physics, may also be applied in other field. Central to the technique is a detector consisting of a bundle of thin, glass capillaries filled with a liquid scintillator of high refractive index. These liquid-core scintillating fibers act simultaneously as a detector of charged particles and as an image guide. Track images seen at the readout end of the capillary bundle are amplified by an optoelectronic chain consisting of a set of image- intensifier tubes and read by a photosensitive CCD camera. We report here on results obtained with detector prototypes. A spatial resolution of 6-14 micrometers , dependent on image magnification prior to readout, has been obtained with 16 micrometers capillaries. The high scintillation efficiency of the liquid scintillator used and a large light attenuation length-- approximately 3 m for 20 micrometers capillaries--result in hit densities along the track of a minimum-ionizing particle of 8.5 mm^-1 and 3.5 mm^-1 at distances from the readout window of approximately 2 cm and approximately 1 m respectively. The radiation resistance of the detector is an order of magnitude greater than that of other types of tracking device of comparable performance. To complement the detector we have been developing a new readout system based around a gateable vacuum image pipeline (VIP) and an electron- bombarded CCD camera. These increase the spatial and temporal resolution obtained with detector and render it particlarly attractive as a microvertex detector for the observation of short-lived particles in high-energy physics experiments performed with evelated interaction rates.

A novel multipoint radiation monitor using waveguide scintillators and optical fiber connections is described. A new design of waveguide scintillator consisting of a scintillating material and a wavelength-shifting fiber (WLSF) has been deeveloped. The WLSF is embedded in the scintillator, and each end is fitted with an optical connector for connection to a transparent optical fiber. Multiple waveguide scintillators can be connected in a series, and the ends of the transparent optical fiber loop are terminated with a pair of photodetectors. This new technique for radiation monitoring dispenses with electric apparatus and improves noise resistance. Furthermore, it offers the advantages of multipoint measurement, meaning that the radiation incident on each scintillator is monitred by two photodetectors. We have examined the light output characteristics and time resolution of a prototype arrangement of waveguide scintillators and confirmed the feasibility of multipoint measurements in a system of five waveguide scintillators connected in series using a 200 m optical fiber loop.

Coded apertures are used in tomographic imaging systems to improve the signal-to-noise ratio (SNR) of the apparatus with a larger aperture transmissions area while maintaining the spatial resolution of the single pinhole. Coded apertures developed from uniformly redundant arrays (URA) have an aperture transmission area of slightly over one half of the total aperture. Computer simulations show that the spatial resolution of a SPECT apparatus using a URA generated coded aperture compared favorably with theoretical expectations and has a SNR that is approximately 3.5 to 4 times that of a single pinhole camera for a variety of cases.

We describe initial results obtained with a prototype small-animal PET imager built with scintillating optical fibers. This device produced images at high resolution, corresponding to the physical limit of positron annihilation imaging. In vivo images in the rat were obtained which were rich in detail and showed good positional correlation with anatomic images of the same animal. The device operated with an initial sensitivity sufficient to detect the biodistribution of PET imaging agents with a 3-5 minute time resolution. The system is undergoing extensive upgrading and testing.

Pacific Northwest Laboratory (PNL) has fabricated cerium-activated lithium silicate scintillating fibers via a hot-downdraw process. These fibers typically have a operational transmission length (e^-1 length) of greater than 2 meters. This permits the fabrication of devices which were not possible to consider. Scintillating fibers permit conformable devices, large-area devices, and extremely small devices; in addition, as the thermal-neutron sensitive elements in a fast neutron detection system, scintillating fibers can be dispersed within moderator, improving neutron economy, over that possible with commercially available ³He or BF₃ proportional counters. These fibers can be used for national-security applications, in medical applications, in the nuclear-power industry, and for personnel protection at experimental facilities. Data are presented for devices based on single fibers and devices made up of ribbons containing many fibers under high-and low-flux conditions.

A hybrid image intensifier zoon tube, based on a thinned backside electron-bombarded CCD (EBCCD) 1024 X 1024 pixels (13.1 X 13.1 micrometers ²), to be used for the readout of a high resolution fiber detector in a high energy physics experiment, has been designed, manufactured and tested. This tube has a photocathode diameter of 40 mm and allows to change the image magnification (M) from 0.6 to 1.3. Owing to the low energy threshold of the EBCCD (2.5 keV) and the high operational voltage (15 kV), a gain (electrons per photoelectron) of 4000 has been attained. A spatial resolution of about 40 lp/mm (15% MTF) with an illumination of 2 (DOT) 10(superscript -4 lux and has been achieved. The EBCCD tube is gateable by applying appropriate voltage pulses to the focusing electrode. The high gain and the excellent space resolution of this device make it very interesting for many applications in high energy physics, astrophysics, medical diagnostics and very low light imaging.

Generation III image intensifiers use an aluminum gallium arsenide/gallium arsenide (AlGaAs/GaAs) heterostructure photocathode that typically sensitive to light in the wavelength range of 550-900 nm. The possibility of improving the performance of Generation III night viewing devices by extending the spectral response into the blue (less than 550 nm) region of the electromagnetic spectrum has stimulated considerable interest lately. This is largely due to the fact that an increase in the blue response of the image tube significantly increases detection, recognition, and identification of targets in sandy or desert terrain. The short wavelength response of the Generation III image tube is primarily dominated by the thickness and composition of the AlGaAs window and the thickness of the GaAs active layer. In this paper, we review the role of the AlGaAs layer to the overall performance of the Gen III image tube and discuss the optical properties of the AlGaAs/GaAs heterostructure. Finally, the overall performance of blue enhanced photocathodes is discussed with data presented on sealed tubes with quantum efficiencies greater than 20% at 500 nm.

We present the development of extended near infrared based image intensifiers with InGaAs semiconductor and multi-alkali based photocathodes having 1.0-1.3 micrometers and 1.0-1.1 micrometers spectral sensitivities, respectively. For the InGaAs based image intensifiers, we study their material characteristics using transmission, photoluminescence, micro-Raman, and scanning Auger spectroscopies. Direct spectral comparison of the InGaAs image intensifiers are made to standard Generation II and III image intensifiers. Then we study the sealed NEA InGaAs image tube performance parameters such as spectral sensitivity, whitelight photoresponse, equivalent background illumination, signal-to-noise, modulation transfer function, and optical system-image intensifier field performance data. For the multi-alkali based image intensifiers, we present a direct spectral comparison of it to our NEA InGaAs and standard super Gen II image tubes. Finally, we examine the advancement of our near infrared devices into the 1.5-2.0 micrometers spectral regime.

We have measured the absolute and coupled system responsitivies of several image intensifier types at several wavelengths in the visible spectrum. Intensifiers characterized include microchannel plate (MCP) generation II proximity-focused and hybrid generation I/generation II electrostatic-focused designs. Configurations including single plate, double plate, nominal and high strip current MCPs, and standard S20 and super generation II enhanced S-20 photocathodes were evaluated. Absolute responsivity measurements were performed using NIST-traceable radiometry instrumentation. The normalized relative sensitivities and were performed using NIST-traceable radiometry instrumentation. The normalized relative sensitivities and overall optical luminous gain performance provided by individual intensifiers when similarly coupled to either high resolution 10-bit RS-170 CCD or FPS camera are presented along with their radiometric data.

The video image of a target submerged in a scattering medium was improved through the use of range gating techniques. The target, an Air Force resolution chart, was submerged in 18 inch of a cloudy solution of tincture green soap and water. The target was illuminated with pulsed light from a Raman shifted, frequencfy-doubled, Nd:YAG laser having a wavelength of 559 nm and a width of 20 ps FWHM. The laser light scattered by the target and soap solution, along with the light reflected by the surface of the tank holding the water, was imaged onto a MCPII. The output from the MCPII was then recorded with a RS-170 video camera and a video digitizer. The MCPII was shuttered on with a pulse synchronously times to the laser pulse. The relative timing between the reflected or scattered laser pulse and the shuttering of the MCPII determined the distance to the imaged region. The resolution of the image was influenced by the MCPII's shutter time. A comparison was made between the resolution of the images with 6 ns, 500 ps and 180 ps FWHM (8 ns, 750 ps, and 250 ps off-to-off) shutter times. It was found that the image resolution increased with decreasing shutter time. The longer exposures allowed more light scattered by the water to be recorded along with the light from the target. The presence of this scattered light in the image increased the noise, thereby reducing the contrast and the resolution.

The modulation transfer function (MTF) of a shuttered, 18-mm-diameter, proximity-focused MCPII was measured as a function of time in the shutter sequence. Electrical gate pulses were delivered to the MCPII with microstrip impedance transformers for reduced pulse dispersion and reflections. Using 30 ps FWHM, 600 nm pulses from a sync-pumped dye, argon-ion laser as a probe, the MCPII's shutter speed (off-off) for point-source (6-micrometers -diameter) illumination and 230 ps FWHM, -590 V gate pulses was measured to be <EQ 250 ps and the FWHM shutter was measured to be as low as 120 ps. The MTF of the MCPII was measured by analyzing the point spread function for inputs at several different locations on the MCPII and at different times in the shutering sequence. The best resolution, a 50% MTF of 16.2 lp/mm, was found with illumination near the edge where the gate pulse enters the MCPII and at 120 ps into the shutter sequence. The shutter speed (off-to-off) of the MCPII with a fully illuminated 18-mm-diameter photocathode was measured to be 270 ps and the FWHM was 160 ps.

The electric characteristics of the linear two-channel bulk charge coupled device (BCCD) with an n-type surface channel and p-type bulk channel of conductivity, located one under another, have been investigated experimentally. The device has sixteen elements of decomposition. THe four-step diagram of control boltage pulses, providing synchronous contrary transfering of charge packages in the channels, has been used. The method of electron holding in the surface channel by the dc voltage of value approximately (- 10.5 divided by 11V) on the lateral electrodes has been proposed. The amplitude of negative control voltage pulses has varied in the interval 0 divided by - 20V with 99.76% of the efficiency of charge transferring at the frequency of 75 kHz in the both channels. In photoelectric measurements the essentially different spectral characteristics of BCCD channel photosensitivities have been found. The maximum of the n-channel photosensitivity falls on the approximately 0.75 micrometers wave length. In general, the principle possibility of a spectrozonal phototransformer creation based on the two-channel BCCD has been shown experimentally.

This paper sums up the results of more than 10 years of experience in design and manufacturing of thinned back-side illuminated CCDs of different types. Based upon the EB- CCDs created, the family of intensified electron-bombardment CCD image tubes has been designed, fabricated, and tested. This family includes: the single-stage Gen I EB-CCD devices with the 532^*580 and 780^*580 pixels CCDs; the 'hybrid' (the EB-CCD tube plus Gen I image intensifier) devices; and the EB-CCD tubes with the 40 mm photocathode and image demagnification factor 3 to 1. The results of the tests of these devices are presented and discussed. Besides this, the near future projects concerning EB-CCD tubes with the 80 mm photocathode and with image demagnification factor 5 to 1, and EB-CCD tubes with solar blind photocathods for the UV and EUV applications are briefly described.

A new class of video rate imagers based on back-illuminated and thinned CCDs is available that shows promise to replace conventional image intensifiers for most military, industrial, and scientific applications. Thinned, back-illuminated CCDs (BCCDs) and electron-bombardment CCDs (EBCCDs) offer low light level performance superior to conventional image intensifier coupled CCD (ICCD) approaches. These new, high performance devices promise to expand the fields of science, provide high contrast, high resolution, low light level surveillance imaging, and make nighttime pilotage safer for military aviators. This paper presents experimental data which illustrates how responsivity, gain, and modulation transfer function (MTF) determine the low light imaging capability, the 'target of interest' signal to noise ratio (SNR) of each of these types of sensors. High SNR and MTF make BCCDs the imager of choice under moderately low light levels and EBCCDs the imager of choice under extremely low light level conditions.

The Rutherford Appleton Laboratory Photon Counting Detector (RALPCD) is a highly adaptable intensified imaging system with applications in the x-ray, EUV and visible wavelength regions. The detector comprises commercially available high gain microchannel plate intensifiers fiber optically coupled to CID or CCD cameras, to form a modular detector arrangement. Frames of data from the cameras are detected and centroided in a transputer parallel processor array where correction algorithms using look up tables are used to produce pattern free images at high resolution. Data from the applications are used to illustrate the performance and future advances are discussed.

For MeV radiography with millimetric spatial resolution and 30% quantum detectivity we are developing a new large sized gamma-ray pixellized scintillator imager composed by an array of long and heavy scintillating crystals. The previous readout device is a parallel plate avalanche chamber, but we do not limit our investigation in the direction of VUV scintilators, and thus we compare the spatial resolutions by means of the Monte Carlo simulations on BaF₂, LiBaF₃, BGO, LSO, and GSO.

1K by 1K UV photon counting array (PCA) imaging detectors have been built for the Space Telescope Imaging Spectrometer (STIS) program by Ball Aerospace in Boulder, Colorado. The STIS detectors are the largest of this type ever produced. These detectors have unique electronic and electro-mechanical requirements. This paper discusses the STIS PCA detector (MAMA detector) charge amplifier and discriminator electronic and packaging requirements. Critical system parameters, including speed, noise, power consumption, and size are described. Cost drivers including fabrication methods, test methods, and production techniques are discussed. Additional cost reduction techniques suitable for ground-based systems will be suggested. System requirements and circuit performance are compared to demonstrate that performance meets or exceeds all system requirements.

The Space Telescope Imaging Spectrograph (STIS), a next-generation instrument for the Hubble Space Telescope, has begun the fabrication of the flight units (plus spares) of the multi-anode microchannel array (MAMA) detectors. STIS will fly two MAMA detectors, one with a CsI photocathode covering the short-wavelength (1150-1750 angstrom) band and a second with Cs₂Te covering the 1650-3100 angstrom band. Good tube yields continue to be realized with many of the MAMAs exceeding flight specifications by substantial amounts in key parameters. Evnironmental testing on the earlier engineering model units (EMUs) demonstrate the ruggedness of the tube design. We present performance results of the STIS flight MAMAs which have been fabricated to date. Life and other engineering tests on EMU detectors will be presented as well.

The Space Telescope Imaging Spectrograph (STIS) uses two 1K by 1K photon counting array (PCA) detector systems. Design of the PCA detector systems is described in this paper. These detector systems are similar in many ways and are mechanical mirror images of each other but cover different UV wavelength bands. A top-down design methodology was used to produce the two detector systems that feature: manufacturability, serviceability to the component level, system-level replacement without optical realignment or calibration, and a high level of parts commonality for cost control. The design meets the Space Telescope's structural, thermal, and electromagnetic compatibility requirements as well as electro-static discharge compatibility requirements of MIL-STD-1686A.

We have investigated the thermal behavior of a set of 40 mm, high strip current, microchannel plate (MCP) photomultipliers developed for a diagnostic system of a fusion plasma by laser scattering. These detectors include a V-stack of very low resistivity (5 X 10⁶ (Omega) m) microchannel plates and must be operated with a pulsed high voltage power supply under strict control of the temperature. Therefore the resistance of the V-stacks has been studied as a function of the MCP temperature and of the applied voltage by applying short pulses of high voltage to the detectors in a temperature comtrolled environment. At low applied voltage (approximately 1 V) a resistance of 2.05 X 10⁶ (Omega) was measured for one of the V-stacks, with a resistance coefficient of -1.47 X 10⁴ (Omega) /degrees C. At high voltage the resistance was found to be lower by about a factor three and showed a linear decrease with both the MCP temperature and the applied high voltage. From these measurements the detector thermal capacitance and thermal conductivity were found to be 0.79 J/degrees C and 1.85 X W/degrees C respectively. The measured parameters are used in a simplified thermal model of the detectors for the construction of the pulsed power supply control system necessary to operate them in safe conditions.

OSL (optically stimulated luminescence/photostimulated luminescence-PSL-) storage phosphors imaging plates are well known to present advantages in terms of sensitivity, spatial resolution, linearity, and signal dynamics in comparison with classical 'scintillating screen- film' packs for radiology (soft x-rays). Are these OSL so useful for high energy (MeV) radiography (non destructive testing or flash radiography)? Experiments show that only linearity and dynamics are better than those of screen-film cells. We present some improvement directions for this promising imager: metallic screens, thicker OSL plate, densification, sensitization methods.

If there is fatigue for an image intensifier, then it has an effect on the imaging property of night vision system. Ill this paper, using the principle of Joule Heat, we derive a mathematical formula for the generated heat of semiconductor photocathode. And we describe the relationship among the various parameters in the formula. e also discuss reasons for the fatigue of generation II image intensifier caused by bigger input illumination. Keywords: fatigue, image intensifier. input illumination.

The design of an automatic system for laser beam alignment and diagnosis is presented. Our conceptual approach to the development of the system is based on the utilization of a multifunctional electro-optic sensor. The system can determine both the energetic-spatial parameters and the spectral content of the source of radiated energy. According to the obtained information, the system is able to control the spatial parameters of the laser beam and to automatically align the optic devices of the laser system. Algorithms are developed which improve the measurement and control accuracy, take into account the influence of the destabilization factors as well as allow to determine the spectral content of the light source on the basis of a quandrant photodiode. Finally, experimental results are presented which confirm the given methods.

The interaction process of a high-power laser and a PIN-junction optoelectronic diode has been studied theoretically and experimentally. It has been put forward that the thermal effect of laser beams and the eroding and washing effect while the laser plasmas expand out, results in the silicon photodiode to be damaged. The thermal distribution, the expression of the maximum temperature, have been obtained for the first time when a Q-switched Nd:YAG laser irradiated upon the PIN junction optoelectronic diode.

Nowadays the applications of image intensifiers are no longer limited to night vision but include a wide variety of industrial and scientific applications. For the latter applications the image intensifiers are nearly always coupled to CCD cameras. The dynamic use of the ICCDs requires the availability of a variety of configurations. We review the possibilities with ICCDs and discuss the influence on the performance of a large number of options.

A small area, imaging, scintillation probe is being developed for locating small amounts of radio-labeled malignant tissue during surgery. Preliminary in brain surgery, avoiding the removal of excess tissue is a priority. It is possible to locate the main body of a brain tumor both before and during surgery, but once the bulk of the tumor is excised the identification of residual malignant tissue is difficult. A probe that covers an area of 1-2 cm² with an intrinsic resolution of 1-2 mm could locate small tumor masses that pose a threat of recurrence of the disease, and prevent removal of healthy tissue. A pre-operative injection of tumor seeking, beta emitting radiopharmaceutical (e.g. ¹⁸fluorodeoxyuridine-FDUR-) will label the tumor. The limited range of beta-rays ensures proximity upon successful detection. Plastic scintillators are used for beta detection, and visible light photon counters (VLPCs) detect the scintillation light. For maneuverability in and around the surgical cavity, the scintillators are coupled to the VLPCs via 2 m of optical fiber. An imaging device can cover the tissue bed in a time compatible with surgery, as opposed to a single element detector on the order of 1-2 mm in size with comparable resolution. An imager also distinguishes high background rates (such as from annihilation gammas in FDUR) and concentrations of activity.

Radiation promotes charge transfer inefficiency (CTI) in a CCD, causing focused images to become smeared. For example, such smearing will degrade the accuracy and precision of a CCD-based pointing system. A model has been created whereby CTI smearing caused by a radiation induced traps can be projected, given the spatial distribution and pixel position of the image, the large signal CTI, temperature, parallel and serial transfer frequencies. It is well known that CTI increases with signal size to some asymptotic level, and the model description offers a theory and function for this behavior. The final product indicates several complicating factors affecting CTI evaluation which could inflate results, and make precise comparisons between experiments.