Analytical considerations and test results bearing on the performance of a CsI(Tl) scintillating crystal coupled with a photodiode when used as a gamma-ray spectrometer are addressed. Laboratory test results on a number of CsI(Tl) bars with different sizes, diffusive coatings, and preamplifier designs are presented. A suitable event selection electronic logic design is shown which reduces the effect of noise on the count rate while retaining the desired energy threshold.

The status of the Objective Crystal Spectrometer (OXS) to be flown on the Soviet Spectrum-X-Gamma satellite together with the X-ray investigation of two of the three natural crystals (LiF(220), Ge(111) and RAP(001) which are chosen as the baseline option are presented. An important result of this study is the approximately 50 percent higher resolution obtained by polishing the LiF(220) surface. The measured X-ray data has been used to determine the OXS specifications. A simulation of the performance of the OXS for the LiF(220)-case are presented. A novel design in which multilayers are coated on the LiF(220) and Ge(111) surfaces is presented. This design allows simultaneous spectroscopy in two energy bands each centered on cosmically interesting line emission regions. X-ray reflectivity measurements demonstrate that the crystal surface can be made sufficiently smooth for the application of the multilayer coating. The first X-ray reflectivity data of multilayers deposited on these surfaces are also reported.

Measurements performance on cylindrical scatterers for focal plane X-ray polarimetry consisting of beryllium capsules filled with metallic lithium are reported. The method used is discussed and evaluated based on the measurements.

A mosaic of high-purity Ge detectors, associated with a mask a few meters above the detector plane, are very promising for future high-energy resolution and source localization astrophysics experiments. This paper describes such a detector and gives its energy resolution vs FET temperature as well as measurements on its localization accuracy. A computer simulation and image reconstruction based on a delta decoding method are also presented.

The concept, operational principle, and test results are presented for a new type of high-pressure high-spatial resolution proportional counter with enhanced spectroscopic capability. The detector in its baseline configuration is to be filled with a xenon/quench gas mixture at 5 bar and is to be sensitive over the 5-150 eV energy range. The position resolution will range from 0.5 mm at the lower energies to around 1 mm at the upper end of the energy range. The very high timing resolution of this new detector allows high count rate capacity and enables the application of the escape gating technique to achieve a high spectral resolution at energies above the xenon K edge.

Measurements of the EUV quantum detection efficiency (QDE) of opaque RbBr, CsBr, and KBr photocathodes are described and investigations of their photoemission characteristics over the 44-1560 A wavelength range are reported. The results show that high QDEs can be obtained in the EUV. Narrow QDE peaks at soft X-ray wavelengths occur at slightly different wavelengths for each of the materials studied. The long-wavelength thresholds vary according to the material band gap. Data on the photoemission from the photocathode layer on the microchannel plate interchannel web area are used to determine the number and energy distribution of the emitted photoelelectrons as a function of wavelength.

The xenon-filled IPCs being developed for the Stellar X-ray Polarimeter are described. The requirements placed on the IPCs by the design of the polarimeter are discussed and results on the performance of prototype counters are presented. The design of a prototype of the IPCs is described. Finally, the performance of the prototype is reported. Due to the extremely low count rates encountered in X-ray polarimetry, efficient background rejection is the most critical parameter of the IPCs. Using a background rejection scheme employing anticoincidence and pulse shape discrimination, a rejection efficiency of 99 percent has been achieved for Co-60-induced events over an energy range of 2 to 15 keV while retaining more than 80 percent of the X-ray efficiency.

The results of an analysis of the background in a fluorescence-gated proportional counter operating over the energy range 3-150 keV are presented. It is found that the dominant background component is that produced by high energy qamma-rays that penetrate the shields and undergo multiple scattering in the detector body, resulting in photoelectric absorption in the detector gas. A careful choice of materials and thickness can move the peak of this emission outside of the detector sensitive range, thereby dramatically reducing the residual background.

EUVITA, an array of eight extreme UV imaging telescopes with normal incidence reflection multilayer coated mirrors with central wavelengths of the individual telescopes between 50 and 250 A, is discussed. The scientific objectives of the EUVITA program are summarized and the instrument configuration and sensitivity are described. The detector electrons and command and the data handling system are briefly addressed.

The capabilities of the European Photon Imaging Camera (EPIC), the main instrument of ESA's 'Cornerstone' mission in X-ray astronomy with multiple mirrors (XMM), are discussed. The CCD characteristics, spatial resolution, energy bandpass and faint source sensitivity, spectral resolution and sensitivity, and timing capability are addressed, and the scientific rationale of the EPIC is summarized. The EPIC instrument system concept is briefly described.

The Array of Low Energy X-ray Imaging Sensors (ALEXIS) experiment consists of six wide angle EUV/ultrasoft Xray telescopes utilizing normal incidence multilayer mirrors, flown on a miniature satellite to map out the sky in three narrow bandpasses around 66, 7 1, and 95eV.The 66 and 7 1 eV bandpasses are centered on intense Fe emission lines which are characteristic of million degree plasmas such as the one thought to produce the soft X-ray background. The 95eVbandpass has a higher throughput and is more sensitive to continuum sources. The mission will be launched into orbit on the Pegasus Air Launched Vehicle in mid-1991. We will present the details of the ALEXIS telescope optical design, initial characterizations of the first flight mirrors and detectors, and the current schemes for characterizing and calibrating the completed telescope assemblies. We will also discuss the details of a novel "wavetrap" feature incorporated into the multilayer mirror structure to greatly reduce the mirror's reflectivity at 304A, a major background contamination flux of He II emission from the geocorona.

The source of an observed diffuse, time-varying structured background component in both bare and coated microchannel plates (MPCs) is investigated. The effects of MCP operating voltages, MCP gain characteristics, pressure, electrical contacts, and physical shielding on this background component are addressed. Various techniques to reduce this background are considered.

Progress is reported in the development and testing of a microchannel-plate anode detector for a satellite-based all-sky survey in the FUV. A preliminary FWHM-resolution value of 6- microns and a linearity of 15 microns have been achieved. Optimization of the electronics should improve the resolution by a factor of four and improve the linearity to 10 microns over the entire field. It should be possible to increase the detector format to hundreds of sq cm with no degradation of resolution or increase in complexity.

Metric nonlinearities in microchannel plate detectors have been mapped using a small spot of UV light scanned across the detector. The centroid of the detected image is accurately located, and corrections to the wavelength scale are made to determine the precise absolute Doppler shifts of the solar emission lines. The possible causes of the observed nonlinearities are briefly discussed.

The multianode microchannel array (MAMA) has been chosen as the detector for two instruments on the ESA/NASA Solar Heliospheric Observatory. The response of the MAMA to the two extreme types of solar spectra, disk and corona, have been modeled with a view toward evaluating dynamic range effects present. The method of MAMA operation is discussed, with emphasis given to modeling the effect of electron cloud charge spreading to several detector anodes and amplifiers (n-fold events). Representative synthetic EUV spectra have been created. The detector response to these spectra is modeled by dissecting the input photon radiation field across the detector array into contributions to the various amplifier channels. The results of this dissection are shown for spectral regions across the entire wavelength region of interest. These results are used to identify regions in which total array photon counting rate or individual amplifier rate may exceed the design limits. This allows the design or operational modes to be tailored to eliminate the problem areas.

Results of the calibration program performed on flight and flight-spare detectors for the Rosat Wide Field Camera (WFC) are presented. The result of an accelerated life test on a development model detector assembled to flight standard are summarized. Imaging tests demonstrate that the lookup table technique for removing distortion works efficiency with low differential nonlinearity. No undesirable 'chicken wire' effects are seen in the images, and the detector resolution matches the on-axis performance of the telescope and is constant across the field of view. Peaks in efficiency occur at 10.2, 20, and 100 eV and mimima at 13 and 45 eV. The secondary 13 eV minimum is correlated with the onset of two-electron photoemission. The mean change in gain as a function of photon energy in the EUV band is much less rapid than in the soft X-ray band.

Large-area thin-film bandpass filters have been constructed to provide four wavelength bands for the Wide Field Camera telescope on the Rosat satellite. The filters consist of a polycarbonate substrate coated with one of carbon, beryllium, or aluminum; additionally, a tin/aluminum filter is also available. These provide wavelength bands of mean wavelength 100, 140, 180, and 600 angstroms, respectively. This paper describes manufacture, and qualification details in the context of filters launched at ambient pressure, with a very stringent requirement for opacity, at around 1800 A, of better than 10 exp-8 of the filter area. Measures taken to protect filters against erosion by low earth orbit atomic oxygen are also briefly presented. Calibration procedures and results are discussed together with comparison of measured transmission profiles with those derived from published absorption coefficients over the range 40 to 2000 A.

The microchannel plate-based High Resolution Imager (HRI) is one of the focal plane instruments of the Rosat X-ray telescope that was launched on 1 June 1990. The calibration of the HRI is reported and preliminary results from the in-orbit calibration are presented. The quantum efficiency of the detector has been determined as a function of energy, the spatial variation of quantum efficiency, geometric nonlinearities, background, imaging performance, and UV sensitivity. Results of periodic tests of the temporal stability of the instrument are also reported.

The basic principles of superconducting tunneling junction (STJ) detectors are summarized and the state of the art in experimental and simulation work involving STJ detectors is briefly examined. Astrophysical applications of STJ detectors are briefly addressed.

We report on the current status of our work on x-ray microcalorimeters for use as high resolution x-ray spectrometers. To maximize the x-ray collecting area and the signal to noise ratio, the total heat capacity of the device must be minimized. This is best achieved if the calorimeter is divided into two components, a thermal sensor and an x-ray absorber. The thermal sensor is a neutron transmutation doped (NTD) germanium resistor made as small as possible to minimize the heat capacity of the calorimeter. The thermistor can be attached to a thin x-ray absorber with large area and low heat capacity fabricated from superconducting materials such as niobium. We discuss results from our most recent studies of such superconducting absorbers and present the x-ray spectra obtained with these composite microcalorimeters at a temperature of 0. 1 K. An energy resolution of 19 eV FWHM has been measured.

The initial development work on a dielectric microcalorimeter is presented. It focuses on the dielectric properties of the ferroelectric material KTa(1-x)Nb(x)O3 (KTN). Measurements of the temperature dependent dielectric constant are given together with the first alpha particle detection results from a prototype composite microcalorimeter operating at 1.3 K. A nonthermal mechanism for detecting 6 MeV alpha particles in a monolithic KTN sample is also reported.

A kinetic inductance thermometer is applied to X-ray calorimetry, and its operation over a wide range of frequencies and geometries is discussed. Three amplifier configurations are described, one using a superconducting quantum interference device (SQUID) amplifier, another incorporating an FET amplifier in an amplitude modulated system, and the third, using a tunnel diode frequency modulated oscillator circuit. The predicted performance of each configuration is presented.

The concept for the 2D position-readout device for the SPAN photon-counting detector is presented with attention to the count rates, spatial resolution, and charge-measurement precision. The electrodes which are deposited on the planar substrate result from charge division induced by a charge cloud, the centroid position of which is encoded by the ratio of charge magnitudes. The SPAN electrode design is analyzed and theorized to permit 1000 x 1000-pixel resolution at 1 MHz. The SPAN spiral-anode six-electrode design is compared to the Vernier-anode twelve-electrode structure for encoding 2D position, and digital precision is analyzed at count rates up to 1 MHz. The SPAN readout affords resolution levels of up to 1/1000 across the entire active area at 8-bit digitization.

Observations of afteremission in microchannel plate (MCP) detectors illuminated by low-energy ions or soft X-ray are reported. Possible mechanisms of delayed pulse generation in lead glass microchannel plate multipliers are discussed with reference to observations with MCPs of different chemical compositions. The findings of the study are discussed in relation to the use of MPC detectors in space astronomy and other fields.

The soft X-ray quantum efficiencies of CsI and CsBr coated microchannel plates (MCPs) are described. These two materials are deposited on an MCP in quadrants. The quadrants are coated with CsI, CsBr, and a mixture of CsI and CsBr. The paper reports on the deposition techniques, background characteristics, imaging quality, and relative quantum efficiency over a selected range of X-ray energies from 0.1 KeV to 4.5 KeV.

Several spherically curved microchannel plate (MCP) stack configurations were studied as part of an ongoing astrophysical detector development program, and as part of the development of the ALEXIS satellite payload. MCP pairs with surface radii of curvature as small as 7 cm, and diameters up to 46 mm have been evaluated. The experiments show that the gain (greater than 1.5 x 10 exp 7) and background characteristics (about 0.5 events/sq cm per sec) of highly curved MCP stacks are in general equivalent to the performance achieved with flat MCP stacks of similar configuration. However, gain variations across the curved MCP's due to variations in the channel length to diameter ratio are observed. The overall pulse height distribution of a highly curved surface MCP stack (greater than 50 percent FWHM) is thus broader than its flat counterpart (less than 30 percent). Preconditioning of curved MCP stacks gives comparable results to flat MCP stacks, but it also decreases the overall gain variations. Flat fields of curved MCP stacks have the same general characteristics as flat MCP stacks.

The European Space Agency X-ray Multi-Mirror mission will be devoted to X-ray imaging and spectroscopy with high throughput. Both the EPIC focal plane camera instrument, and the RGS dispersive spectrometer require detectors with high sensitivity in the soft X-ray waveband. A description of

Available photodiodes are reviewed with attention given to the performance parameters, temporal stability, and appropriateness for narrow bandpass applications and certain photon energies. The configuration of XUV photodiodes for use in the EUV and soft X-ray regions is delineated, and the measured parameters are outlined. The photodiodes have stable efficiencies that vary linearly with photon energy and exceed 1 electron/incident photon for photon energies of at least 10 eV. The silicon photodiodes are found to be suitable for EUV and soft X-ray applications and are stable, very highly efficient, and are unaffected by operation under high gas pressures. The silicon dioxide outer surface can be coated with thin films to develop narrow bandpass applications. The present XUV silicon detectors have active areas of 1 or 3 sq cm and can be used with an instrument for measuring photocurrent without external power supplies.

An examination is conducted of the effects of low-energy protons on CCD performance to evaluate the potential effectiveness of space-borne observational instruments. Degradation is described as a function of incremental dose, irradiation temperature, or proton energy for several device architectures, some of which incorporate design features to minimize signal-charge/trapping-site interaction. Degradation of the charge transfer is studied for very low proton doses, and dark current is found to vary directly with proton dose. Displacement damage in the signal-transfer channels generates charge-trapping sites that have a negative effect on EEV CCD performance. Degradation of charge-transfer performance is shown to be the most significant hindrance to effective CCD operations for X-ray spectroscopic applications.

Recent results on the on-chip electronics, transfer properties, and radiation entrance window of pn-CCDs are presented. With recently fabricated devices, an improved charge transfer efficiency per pixel of 0.9995 and an energy resolution of the CCD output stage of 5 e(-) rms have been measured. This performance is achieved without a degradation of other characteristics of the devices, such as an X-ray efficiency of 90 percent at 10 keV, more than a factor of 1000 better time resolution in the full frame mode in comparison with all other CCD concepts, and a one-dimensional spatial resolution of 24 microsec in the timing mode. The use of pn-junctions instead of MOS structures makes the devices intrinsically radiation resistant.

The Research Amplifying Imaging Detector consists of a microchannel plate image intensifier with a thin coating (3500-10,000 A) of the phosphor tetraphenyl-butadiene (TPB) on the entrance window to convert EUV radiation to visible, and coupled via a lens to a CCD detector. This design allows great flexibility in selecting the pixel size and field of view, with a simple mechanical design. The phosphor appears to be quite rugged, with no degradation having appeared during several months of testing both in and out of vacuum. Tests have been made at visible and EUV (304 A) wavelengths of the following performance aspects: EUV spectral sensitivity, spatial resolution (both of components and of the system as a whole), noise, linearity, and dynamic range. An improved detector for the Coronal Diagnostic Spectrometer experiment on the Solar Heliospheric Observatory satellite is being presently designed.

The general design and performance characteristics of a 1-m diameter f/1.4 normal incidence X-ray Multilayer Telescope (XMT) operating at 0.13 keV are described. The principal scientific objectives of the XMT include soft diffuse X-rays, stellar surveys, interstellar dust grains, and soft excess in AGN. The feasibility of meeting these objectives using an XMT telescope is assessed.

The compact photon-counting detector SPAN is described which offers 25-micron spatial resolution and a 25-mm imaging diam. The SPAN detector incorporates position readout within a vacuum-sealed optical-intensifier tube, and a photocathode is used to sense the images with high-blue and near-UV sensitivity. A microchannel-plate intensifier generates an electron cloud that is measured with a position-sensitive readout developed for this application. The position-sensitive readout is a conductive device that, in the context of the SPAN, permits a high count rate and spatial resolution greater than the charge-measurement precision of each electrode. Preliminary photon counting is demonstrated, and the results suggest that the SPAN has a resolution of better than 1/1000 and effective linearity with 8-bit digitization.

Consideration is given to a new type of position-sensitive MultiWire Proportional Counter proposed as the high-energy instrument for the Spectrum X-Gamma Satellite. Two of them are based on high-throughput X-ray optics, sensitive up to about 20 keV. The third one, MART-LIME, is the high-energy instrument to cover the band 5-150 keV. This X-ray observatory-class orbiter comprises three major coaligned instruments. The scientific objective of this hard X-ray telescope is to produce sky images with arcmin angular resolution and good spectral resolution and submilliCrab sensitivity, during a typical observation time of 100,000 sec. The MART-LIME experiment is expected to produce a breakthrough in high-energy astrophysics by means of deep observations over a wide field of view. The missions are to produce a complete hard X-ray catalog, which is still nonexistent at the milliCrab sensitivity level.

A single high-energy instrument based on rotating modulation collimators with germanium semiconductor spectrometers as the detectors can provide high angular resolution (< 1 arc sec), high time resolution (< 1 s), and high spectral resolution (about one keV), all in one package. Such rotating modulation- collimator optics provide excellent spatial (u,v)-plane coverage for high-contrast images in the hard X-ray domain, where there will be a large signal-to-noise ratio during even modest flares. The use of thick modulation plates will make it possible to image gamma rays with < 5 arc sec angular resolution to energies in excess of 10 MeV during the more energetic flares without compromising the ability of the germanium detectors to resolve the gamma-ray lines. Energetic neutrons will also be imaged for the first time with < 20 arc sec angular resolution. This combination of imaging and spectroscopy at high resolution will be a powerful tool for helping to answer central questions of solar flare physics, especially if such an instrument were supported by observations at longer wavelengths. The timing of solar activity dictates a launch of such a High-Energy Solar Physics (HESP) mission by 1998.

The optical principles associated with spatial heterodyne spectroscopy (SHS) are described and the results of proof-of-concept tests performed in both the visible and the UV spectral regions are presented. A specific all-reflecting SHS configuration now being developed for high-resolution planetary Lyman-alpha studies is discussed. The expected performance of SHS systems is compared to that of conventional instrumentation in two cases: Venusian Ly-alpha measurements at high resolution from a sounding rocket and the velocity-resolved survey of the diffuse FUV interstellar medium emission from a Small Explorer class satellite.

Four position sensitive proportional counters will be delivered by the Danish Space Research Institute as focal plane instruments for the Soviet Danish Roentgen Telescope SODART. These detectors will incorporate the novel microstrip electrode design. This design has been tested with Xenon gas and an Fe-55 X-ray source. The energy resolution is better than 14 percent FWHM up to gas gains of 10,000, the rise time of pulses from X-ray events is fast, 100 ns, allowing for efficient background rejection by rise time analysis. A position resolution of 1 mm FWHM is easily obtained by resistive charge division of the signals from the cathodes and from a wire grid placed in front of the microstrip plate. The detector performs without significant degradation of gain or energy resolution at fluxes exceeding 10 exp 6/s sq cm and a total dose of 10 exp 11 photons.

The scientific goals and the principal design features of the Silicon X-ray Array (SIXA) detector to be flown on the Spectrum-X-gamma satellite are briefly reviewed. The SIXA detector has 19 parallel amplifier channels and an estimated resolution of 170-180 eV at 6 keV. Several measurement modes are available for different scientific measurements. The high sensitivity, broad energy range, and good resolution of the SIXA detector will provide high-quality, time-resolved X-ray spectra from a large sample of astronomical objects.

The Energetic X-ray Observatory on Space Station (EXOSS) is a mission concept for high-sensitivity coded-aperture sky surveys and studies of the spectral and temporal behavior of astrophysical sources from approximately 3 keV to 1 MeV. The scientific motivation for the mission and the instrument requirements, including the need for high angular resolution to resolve and identify numerous detectable sources, are summarized. Two baseline telescopes are described: one employing a 1.4-sq-m array of Xe gas imaging proportional counters to cover the 3 to 100 keV range with 1 arcmin resolution; the second using a 2.8-sq-m array of NaI/CsI imaging phoswich detectors to span the 20 keV to MeV range with 12 arcmin resolution.

The optimum choice of a shield for space-borne gamma-ray spectrometers is investigated using Monte Carlo simulations. The results demonstrate that, for a given spectrometer configuration, a 'best' shield thickness exists which optimizes the spectrometer's background noise and increases its sensitivity. Such an optimization is achieved by a good understanding of the background sources of the spectrometer, and it varies from detector to detector and orbit to orbit. In general, a highly eccentric orbit is consistently better than LEO with regard to the leakage photon background. BGO seems to be a better shield material than CsI if multiple site events selection is applied.

Methods to make ultrathin low-leak X-ray entrance windows, which can withstand atniospheric pressures, have been developed. The first prototype windows have been 6 mm or 20 mm diameter windows with film thicknesses 0.5 m - 2.5 jm of polyimide and 40 ma - 100 nm of aluminium. Also 1 m thick beryllium windows with diameter 6 mm have been made. Our goal is to fabricate 140 mm diameter windows for Danish-Finnish position sensitive proportional counters to be flown on the Spviet SPECTRUM-X-GAMMA satellite.

A new approach to study the composition of microchannel plate sensitive surface by secondary ion mass spectrometry is described. The time-of-flight technique is implemented in an unconventional way which permits using the continuous probing beam and concurrent multichannel mass identification. This makes the technique relatively simple, and the low doses and low probing beam intensities provide the opportunity to perform nondestructive analysis of thin layers and fragile films.

A low contamination vacuum chamber and camera head built to test the ultraviolet and extreme ultraviolet response of charge-coupled devices are described. The vacuum chamber is of all electropolished stainless steel construction with copper seal flanges used throughout. The camera head includes a liquid-nitrogen-cooled, resistively heated thermal control system (+/- 0.1 C), and a specially recast epoxy ZIF socked. All electronic components, except wiring, are kept outside of the vacuum, eliminating major sources of organic contamination. The system is turbopumped and reaches pressures of about 10 exp -8 torr. Residual gas analysis of the system shows that partial pressures of organic contaminants are less than about 10 exp -9 torr.

The technological development of the Medium Energy Gas Scintillation Proportional Counter (MEGSPC), a part of the scientific payload of the Italian-Dutch X-ray Astronomy Satellite SAX, is presented. The detector and the experimental setup are briefly described and its detector performance characteristics are given. Experimental findings on the background resolution and spatial resolution are reported and the background rejection is discussed.

SAX (X-Ray Astronomy Satellite) is a programme jointly developed by the Italian Space Agency (A.S.I.) and the Netherland Agency for Aerospace Programmes (NIVR) devoted to systematic, integrated and comprehensive studies of galactic and extragalactic sources in the energy band 0. 1 - 200 KeV. Scientific objectives are: - Imaging (with moderate angular resolution of 1 arcmin) and broad band spectroscopy over the energy range from 0. 1 to 10 KeY. - Spectral measurements, spectroscopy and timing on sources from 3 to 200 KeY. - All sky monitoring (2-30 KeY) for the investigation of long time variability and localisation and study of transients. The payload complement includes: a low energy (0. 1 - 10 KeY) concentrator/spectrometer (LECS), a medium energy (1-10 KeY) concentrator/spectrometer (MECS) consisting of three units, a high pressure gas scintillation proportional counter (3- 120 KeY) (HPGSPC) and a phoswich detector system (15-200 KeY) (PDS), all of which have narrow fields of view and have the optical axis coaligned to the same pointing direction. Two wide field cameras (2-30 KeY), field of view 20°x20° (WFC) which point in diametrically opposed directions perpendicular to the narrow field instrument axis, complete the payload. The SAX mission is, for the Payload and Science, under the responsability of a Consortium of Italian Institutes with the partecipation of the Space Research Institute of Utrecht/SRONHolland and the Space Science Department of the European Space Agency (E.S.A.). The spacecraft has a total mass of 1200 Kg, is three axis stabilised and it will be placed into a circular orbit at 600 Km with an inclination of two degrees, by an Atlas G-Centaur. SAX, to be launched at the end of 1993, will have a minimum mission life time of two years, extendable up to four years.

The results of a Monte Carlo study of a hard X-ray concentrator for space astronomy are presented. This report is a part of a systematic study devoted to investigate the possibility of utilizing the Bragg diffraction technique to concentrate hard X-rays. In the Monte Carlo study a concentrator made of confocal mirrors with paraboloidal shape is considered. The mirror material is graphite (002) with mosaic structure. The main photon interactions of hard X-rays with the concentrator are simulated. Effective area and optical properties of a particular configuration of concentrator with shape that could be easily accommodate on the Space Station or aboard a free-flyer are given. Expected performances are discussed.

This paper discusses the optimization of the performance of imaging scintillation detectors used in the hard X-ray/soft gamma-ray (20-300) keV region of the spectrum. In these devices, absorption of an incident gamma-ray within an alkali halide crystal induces a scintillation light distribution which is centroided by an imaging photomultiplier tube mounted to the crystal. The ultimate imaging resolution is strongly affected by the detailed propagation of the scintillation light within the crystal and at the interface between the crystal and the phototube face plate. A number of refined techniques for preparing the scintillation crystals so as to optimize the imaging resolution have been investigated. The results indicate very good agreement with relatively simple models of the light propagation. It is shown that it is possible to achieve resolution consistent with the most optimistic models.

The Ultra Violet Auroral Imager (UVAI) project, which will use two UV cameras on a satellite to make overview images of the Aurora Borealis, is discussed. The project's purpose and UVAI band sensitivity are briefly addressed, and the UVAI intensifier is examined in detail. The test setup and the typical UVAI characteristics are given.

The main design features and the early findings of the Rosat XUV wide field camera (WFC) are discussed. The most important data on the WFC telescope and detectors are presented. The WFC operational features, observing efficiency, filter performance, thermal performance star tracker performance, and single-event upsets are discussed. The first WFC images are compared with preflight calibration data.