Hard x-rays (10-500 keV) are produced by cosmic sources such as the Crab nebula and solar flares. Imaging these x-rays will allow insight into the processes at work in these energetic sources. Presently, a Fourier telescope design is flying on the Japanese Solar-A satellite providing hard x-ray images of the Sun, and Fourier designs are being considered for the next generation of high energy observing instruments (e.g., High Energy Solar Physics (HESP)). Current solar flare theoretical literature indicates a desire for spatial resolutions down to 1 arcsecond, fields of view greater than the full solar disk (i.e., 32 arcminutes), and temporal resolutions down to 1 second. Although the Sun typically provides relatively high flux levels, the requirement for 1 second temporal resolution raises a question about the viability of Fourier telescopes subject to the aforementioned constraints. Given sufficient sensitive areas, Fourier telescopes are promising concepts for imaging solar hard x-rays. In keeping with this new era of better, faster, cheaper space science missions, a new, virtual grid Fourier telescope approach is discussed. Given an appropriate detector configuration (i.e., 1D imaging detector), one grid may be eliminated completely from this new telescope. For gamma ray and perhaps hard x-ray imaging, this simplification should prove very useful especially in this new era of smaller space science missions.

We investigated the theoretical performance of a rotating modulation collimator (RMC) situated in front of a moderate angular resolution focusing X-ray telescope. By ray tracing we investigated the RMC's ability to improve the positioning capability and reduce the incidence of source confusion. The moderate angular resolution (two arcmin) telescope can have high collecting area; the factor of four reduction due to the RMC would leave the system with about as much throughput as a high angular resolution telescope of comparable dimensions. This system is likely to be lighter and less costly to construct than a high resolution telescope and could operate over the entire field of a very wide field of view telescope. The wire thickness and spacing are only slightly finer than those of previous RMC's. The effects of possible errors in wire spacing and misalignments of the two wire planes, of the RMC are included in the simulations. Diffraction is also included. Results are encouraging. With 100 detected source counts plus background, we obtain positions with a statistical error below 5 arcseconds. We can resolve and position two, 400-count point sources 25 arcseconds apart. However, this system does not improve upon the telescope resolution in the case of extended sources such as clusters of galaxies.

The Unconventional Stellar Aspect (USA) experiment on the Advanced Research and Global Observations Satellite (ARGOS) of the Space Test Program is a low-cost, quick, yet scientifically ambitious X-ray timing experiment. The research program emphasizes observing neutron stars and black holes for extended periods with sub-millisecond timing resolution. The scientific program is achieved using hardware whose key features are large collecting area (2000 cm²), energy response extending as low as 1 keV, long accumulated observing times (1 month), high time resolution (1 microsecond(s) ), absolute time-tagging (also to 1 microsecond(s) ) achieved using a GPS receiver, sustained high data rates (40 kbps at all times supplemented by 128 kbps as needed), and flexibility in data handling by using a solid state recorder and a radiation- hardened 20 MIPS 32-bit onboard computer to provide onboard processing.

The Advanced X-Ray Astrophysics Facility (AXAF) is a high spatial resolution X-ray observatory scheduled for launch in 1998. One of its two focal plane instruments is the High Resolution Camera (HRC). The HRC consists of two microchannel plate detectors with photocathodes of CsI and KBR, respectively. Current approaches to modeling the HRC detector efficiency have focused on the response of the photocathode over the energy range 0.1 to 10 keV. In this paper, we present recent laboratory measurements of the quantum efficiency of coated and uncoated microchannel plates as a function of energy and angle of incidence of the X-Ray. An empirical model is fit to the data, and the results are used to predict the efficiency of HRC at the focal plane.

We discuss a very high resolution imaging microchannel plate (MCP) detector developed for use in a high resolution ((lambda) /(Delta) (lambda) equals30,000) ultraviolet spectrograph which will fly aboard a NASA sounding rocket. The detector utilizes hybrid anode, referred to as a double delay line, which encodes x-axis position from time delay measurements and y-axis position by charge division. The detector uses low resistance MCP's in a z-stack arrangement to achieve high local count rates and a gain of 2 X 10⁷ electrons per incident photon. The detector has a resolution of 20 micrometers FWHM throughout a 6x1 cm active area. The use of a KBr photocathode and a repeller grid boosts the quantum efficiency of the bare MCP's to over 40% at approximately equals 1100 angstroms.

The Extreme Ultraviolet Explorer (EUVE), launched June 7, 1992, conducted an all-sky survey in the extreme ultraviolet wavelengths (70-760 angstrom) for 6 months and is now performing spectroscopic pointings for Guest Observers. The seven microchannel plate (MCP) detectors used on the instrument (four for imaging in photometric wavebands and three for the spectrometers) have operated successfully throughout the mission. The long-term (780 days) performance characteristics such as quantum efficiency (QE), gain, and background count rate, will be reviewed along with other interesting unexpected effects noted during the mission. Because the QE has remained constant, the background has been reduced, and other effects have been minimized, the EUVE instruments currently operate better than after launch and will probably continue to do so.

The High Resolution Camera (HRC) is one of two focal plane instruments on the Advanced X-ray Astrophysics Facility, (AXAF). AXAF is a major NASA space observatory and is scheduled for launch in 1998. The HRC consists of two detectors; the essential element in each HRC detector is a chevron pair of microchannel plates (MCPs). The MCPs provide x-ray conversion and electron multiplication while maintaining high spatial and temporal resolution. This paper reports on the procedures and results obtained in testing and evaluating candidate flight MCPs.

Microchannel plate based detectors with cross delay line image readout have been rapidly implemented for the SUMER and UVCS instruments aboard the Solar Orbiting Heliospheric Observatory (SOHO) mission to be launched in July 1995. In October 1993 a fast track program to build and characterize detectors and detector control electronics was initiated. We present the detector system design for the SOHO UVCS and SUMER detector programs, and results from the detector test program. Two deliverable detectors have been built at this point, a demonstration model for UVCS, and the flight Ly (alpha) detector for UVCS, both of which are to be delivered in the next few weeks. Test results have also been obtained with one other demonstration detector system. The detector format is 26mm x 9mm, with 1024 x 360 digitized pixels,using a low resistance Z stack of microchannel plates (MCP's) and a multilayer cross delay line anode (XDL). This configuration provides gains of approximately equals 2 X 10⁷ with good pulse height distributions (<50% FWHM) under uniform flood illumination, and background levels typical for this configuration (approximately equals 0.6 event cm^-2 sec^-1). Local counting rates up to approximately equals 400 event/pixel/sec have been achieved with no degradation of the MCP gain. The detector and event encoding electronics achieves approximately equals 25 micrometers FWHM with good linearity (+/- approximately equals 1 pixel) and is stable to high global counting rates (>4 X 10⁵ events sec^-1). Flat field images are dominated by MCP fixed pattern noise and are stable, but the MCP multifiber modulation usually expected is uncharacteristically absent. The detector and electronics have also successfully passed both thermal vacuum and vibration tests.

We describe our recent synchrotron measurements of microchannel plate (MCP) quantum detection efficiency made in pulse-counting mode in a 40-300 eV band containing the L shell absorption edges of silicon. The significance of this data for the calibration of the HRC-S transmission grating detector for the AXAF-I X-ray observatory is discussed.

An active program is underway at MSFC to develop microstrip proportional counters for x-ray astronomy. This work can be divided into two categories: 1) the current fabrication and testing of a large area device (30 cm x 30 cm) for a balloon program and 2) an investigation into the general properties of microstrip proportional counters to provide optimized devices for future missions. This paper includes results from both these areas.

A hybrid detector is under development for use as a balloon-borne instrument in hard x-ray astronomy. The detector provides broad band coverage by coupling an optical avalanche chamber to a phoswich. The optical avalanche chamber yields superior instrument response at low energies while the scintillator takes over at the higher energies where the gas becomes transparent: at 25 keV, the addition of the gas chamber improves the energy resolution by a factor of 2.5 and the spatial resolution by a factor of 10 as compared to the stand-alone response of the phoswich. A half-scale prototype instrument is being constructed for test purposes and to help resolve a number of design questions involving the coupling of the two components.

A large-volume (3 liters), xenon-filled, gas proportional scintillation counter with a curved grid and focusing rings was developed and tested with hard X-rays. The efficiency at 60 keV was calculated to be 64%. The experimentally measured energy resolution was observed to decrease from 6 to 5% when the X-ray energy was increased from 22.1 to 59.6 keV. Spectra are presented for the ²⁴¹Am gamma rays and lanthanum K_(alpha ) and B_(beta ) X-rays. Spectra for the same K lines of erbium, praseodymium and tin are also presented for the detector with and without the focusing rings. These spectra show that the focusing rings increase the detection efficiency and improve the energy resolution. This effect is attributed to the increased electron collection in the scintillation region, to faster pulse rise times and to reduced electron attachment to impurities.

Proportional counters are widely used as X-ray detectors both on the ground and in space. Previous proportional counter designs utilized entrance windows made of stretched polypropylene which have relatively large leak rates for the gases used in the detector. Thin polyimide windows have been fabricated at MIT with low leak rates (3 x 10 E-9 mbar 1/s) and useful X-ray transmission properties down to 0.6 keV energy photons. We report on 1 micrometers thick windows made of silicon-rich LPCVD silicon nitride which have been made with leak rates below our detectable limit. The window fabrication process and test apparatus will be described. Data will be presented on leak tests and mechanical strength of thin windows fabricated from polyimide and silicon nitride. These windows could allow fabrication of a sealed proportional counter, thus eliminating the need for a gas replenishing system in space-based X-ray detectors.

Design, construction, and sensitivity estimates for the performance of proportional counters customarily neglect the consequences of the finite path length of electrons resulting from the primary interaction between the incident x-ray and the proportional counter gas. In many situations this can lead to errors in response functions as a result of ignoring 'charge sharing' between adjacent proportional counter cells which are held in anti-coincidence, or charge lost by the electrons escaping the gas volume into the detector window or into inactive regions. We illustrate the importance of these effects with Monte-Carlo simulations.

We describe a simple Gas Scintillation Proportional Counter for laboratory usage built at the G.S. Vaiana Observatory in Palermo. Its spectral resolution (about a factor 2 better than traditional Gas Proportional Counters), the easy realization and its relatively moderate cost make it a valid alternative to Gas Flow Proportional Counters for the detection of soft X-rays when an improved energy resolution is required.

The High Energy Transmission Grating spectrometer (HETG) on the Advanced X-ray Astrophysics Facility (AXAF) requires the fabrication and assembly of hundreds of large area (approximately equals 6 cm²), low-distortion, ultra-fine-period transmission gratings efficient in the 0.4-10 keV band ((lambda) equals 1.2-30 angstroms). The spectrometer requires two types of gratings: Medium Energy Gratings (MEG), which have a period of 0.4 micrometers and consist of gold bars 0.4 micrometers thick, and High Energy Gratings (HEG), which have a period of 0.2 micrometers and consist of gold bars 0.7 micrometers thick. Both types are supported by 0.5-1.0 micrometers -thick polyimide membranes. The gratings are fabricated using a variety of techniques including interference lithography, tri-level resist processing, reactive-ion etching, and gold microplating. An earlier approach which utilized x-ray lithography has been abandoned. Recent efforts have focussed on improving the yield and robustness of the many complicated fabrication steps, and improving the profile of the grating bars. We present details of the fabrication procedure and discuss the issues associated with developing an optimal fabrication process.

As part of the calibration for the High Energy Transmission Grating Spectrometer (HETGS) on AXAF, we conducted several studies at synchrotrons in an effort to measure the resolving power and the quantum efficiency of gratings over a range of x- ray energies. Gratings that have been thoroughly studied can be used as calibration transfer standards at MIT to evaluate the quality and repeatability of our testing procedures. Synchrotron studies also enable us to evaluate our theoretical prediction of grating performance and thereby obtain a more accurate model of the gratings. In this paper we discuss studies made of 0.2 micrometers and 0.4 micrometers period gratings with gold grating bars supported by thin polyimide films. The goal of this experiment was to measure and accurately model the efficiencies of several grating facets over much of the energy range for which they would be used in space. Our tests were performed in January and July of 1994 at the National Synchrotron Light Source at Brookhaven National Laboratory. We used beam line X8A to illuminate sample gratings that were inserted in the UC/SAO Reflectometer Test Station (the same device that is used to study witness samples for the AXAF mirrors). A double crystal monochromator was used to select narrow energy bands over the range 0.6-6 keV. We measured the diffraction efficiencies as a function of energy for the first order x-rays. Results are in good agreement with predicted efficiencies calculated using gold optical constants that we recently measured, and confirm the energy shift of the MIV and MV edges from the standard values, as measured by Blake et al. (J. X-ray Sci. Technol., in press).

The High Energy Transmission Grating Spectrometer (HETGS) is one of the scientific instruments being developed for NASA's Advanced X-ray Astrophysics Facility (AXAF), scheduled for launch in 1998. The HETGS will be capable of measuring spectra with high resolution and sensitivity from a variety of compact and slightly extended cosmic X-ray sources. In this paper we describe the overall design of the HETGS and its expected scientific performance. The HETGS consists of two arrays of gold grating elements (High-Energy gratings [HEGs] and Medium-Energy Gratings [MEGs] which are optimized for the energy ranges 0.8-10 keV [HEG] and 0.4-5 keV [MEG]). The details of the grating elements and their fabrication methods are described in Schattenburg et al. (this conference). The gratings are mounted on a support plate which can be inserted immediately behind the AXAF telescope assembly. X-rays diffracted by the gratings are dispersed onto the focal plane detector strips which are components of either of the two AXAF imagers (the HRC or ACIS). The two kinds of gratings are oriented at a slight angle with respect to each other so that the dispersed spectra form a shallow 'X' on the readout device. The gratings and detectors are mounted on a Rowland torus to correct for most of the optical aberrations. The grating-detector combination achieves resolving powers (E/(Delta) E) as high as 1000 at some energies, and has significant effective area (10-200 square cm) for all energies 400 eV < E < 10 keV.

We describe the X-ray Astronomy Calibration and Testing Facility of the Osservatorio Astronomico di Palermo G.S. Vaiana. The facility, including a 16 meter vacuum beam line, a 1 m diameter test chamber, a X-ray source system, X-ray detectors, an advanced data acquisition and control system and other minor tools and accessories, features characteristics of vacuum cleanliness and versatility almost unique among facilities of this size. It started operating in June 1993 and will soon be completed with further equipments to improve energy resolution and to extend its capabilities to the UV band up to wavelengths of the order of 3100 A. Possible applications are test and calibration of filters, development and calibration of detectors, reflectivity measurements, testing of small X-ray telescopes. Presently it is employed for the calibration of UV-Ion shields of the High Resolution Camera of AXAF-I.

The Advanced X-ray Astrophysics Facility (AXAF) is a major NASA space observatory (launch 1998). One of its two focal plane detectors is the High Resolution Camera (HRC) assembly consisting of two microchannel plate (MCP) based detectors. Key components of the two HRC detectors are UV/Ion shields consisting of metalized sub-micron plastic membranes, designed to prevent UV light and positive ions from reaching the detectors' sensitive surfaces. We discuss the design issues and present results of recent measurements and tests. Soft X-ray/UV transmission measurements have been conducted at the Space Science Laboratory (SSL), University of California at Berkeley, and at the Osservatorio Astronomico di Palermo G.S. Vaiana, Italy, on sample films of different plastic materials under study, namely Lexan, Polyimide, Parylene-C, and VYNS. Acoustic tests of baseline design UV/Ion shields' samples have been conducted at the Marshall Space Flight Center (MSFC). Computer simulations have been conducted to estimate the HRC count rate due to diffuse UV background and Hot stars.

The High Resolution Camera, or HRC, is a set of microchannel plate based detectors designed to fly aboard the Advanced X-Ray Astrophysics Facility (AXAF), a major NASA space observatory. It will undergo a series of calibration tests before launch in September 1998. The overall calibration is planned in three phases: tests performed before delivery, end-to-end testing at Marshall Space Flight Center, and post launch calibration observations. In this paper, we examine the planned calibration program for the HRC, focusing on laboratory and synchrotron tests to be made before delivery.

The 336 individual grating elements making up the High-Energy Transmission Grating (HETG) will be verified and calibrated in laboratory facilities at MIT as they are fabricated. A high instrument resolving power of order E/(Delta) E approximately equals 1000 requires an overall period uniformity of better than 250 ppm. To extract the maximum astrophysical information the diffraction efficiency of the HETG will be calibrated to the 1% level (1(sigma) ). Grating element period variations are measured and mapped in the Laser Reflection facility. Collimated HeCd (3250- angstrom) or HeNe (6328-angstrom) laser light is diffracted by the samples and measured. A per-point measurement noise of below 5 ppm rms and an overall period repeatability of 40 ppm rms have been achieved. X-ray diffraction efficiency in the 0.4 to 10 keV range is calibrated in the X-ray Grating Evaluation Facility (X- GEF). The facility combines a 17 meter vacuum beam line, a multi- anode X-ray source with monitor counter, a piezo-deformed 1D Ir coated focussing optic, a single-pixel solid state detector, and a 2D imaging proportional counter. The facility operation is under computer control and test procedures, instrumentation parameters, and acquired data are managed with a database. The system uses synchrotron-calibrated reference gratings as efficiency transfer standards. Detailed characterization and modeling of the X-GEF components and test/analysis procedures are being carried out to optimize the quality of the HETG calibration.

It is proposed to use thin films of silicon carbide as Extreme Ultraviolet bandpass filters transparent within 135-304 A band and with excellent cutoff blocking of the strong L_(alpha ) 1216 A line radiation. Mesh or particle track porous membrane supporting 200-800 A thickness SiC filters have been made by RF sputtering techniques. We describe the design and performance of these filters. Such type SiC filter was used in front of the microchannel plate detector of the TEREK X-Ray Telescope mounted on the Solar Observatory CORONAS-I which was successfully launched on March 2, 1994.

The Extreme Ultraviolet Explorer (EUVE), launched on June 7, 1992, is an extremely successful NASA astrophysics mission that contains three extreme ultraviolet (EUV) spectrometers designed to be used in pointed spectroscopic observations of astrophysical sources in the 70-760 angstrom wavelength region. The spectrometers utilize a slitless design based on grazing- incidence optics and variable line-space gratings. Detailed wavelength scales determined from ground-based calibrations and refined with in-orbit data are used to assign wavelengths for each detected photon to within half a resolution element (less that 0.8 angstrom in all cases). Spectral resolving power (FWHM of non-Gaussian profiles) varies in the range R approximately 150-450. Spectrometer throughputs were determined from an extensive laboratory calibration and then were adjusted slightly based on in-flight calibration spectra of known astrophysical continuum sources (hot DA white dwarf stars). We also have measured count rates from the detector and the geocoronal and distributed backgrounds, parameters critical to assessment of accurate flux levels from the astrophysical sources.

The Array of Low Energy X-ray Imaging Sensors (ALEXIS) satellite is Los Alamos' first attempt at building and flying a low cost, rapid development, technology demonstration and scientific space mission. The ALEXIS satellite contains the two experiments: the ALEXIS telescope array, (which consists of six EUV/ultrasoft x- ray telescopes utilizing multilayer mirrors, each with a 33 degree field-of-view), and a VHF ionospheric experiment called Blackbeard. A ground station located at Los Alamos exclusively controls the spacecraft. The 248 pound ALEXIS satellite was launched by a Pegasus booster into a 400 x 450 nautical mile, 70 degree inclination orbit on April 25, 1993. Images from a video system on the rocket indicated that ALEXIS had been severely damaged during launch with one of the 4 solar panels breaking away from its mounting. (It later turned out that the solar paddle was still attached to the spacecraft but only through cable bundles.) Attempts at communicating with the satellite were unsuccessful until a surprised ground crew received a short transmission on June 2. By mid July, ground station operators had regained full control of the satellite and began to initiate scientific operations with both the telescope array and the VHF experiment. In this paper we will discuss a preliminary analysis of the on-orbit performance of EUV telescopes on ALEXIS.

We are developing a field-widened Spatial Heterodyne Spectrometer (SHS) for suborbital observations of the hot component of the diffuse interstellar medium. Our goal for these observations is to obtain the first velocity-resolved (20 km/s) line profiles of the CIV 154.8 nm emission line from the Cygnus loop and from one direction at high galactic latitude. Long term, our interest is to develop an SHS instrument for a radial-velocity-resolved sky survey of the 10⁵ K 'coronal gas' component of the interstellar medium using a small satellite. We describe the basic SHS technique along with vacuum ultraviolet demonstrations using our prototype interferometer. We also describe a new data reduction technique which corrects for instrumental distortions resulting from optical defects.

UVSTAR is an EUV spectral imager intended as a facility instrument devoted to solar system and astronomy studies. It covers the wavelength range of 500 to 1250 angstrom, with sufficient spectral resolution to separate emission lines and to form spectrally resolved images of extended plasma sources. Targets include the Io plasma torus at Jupiter, hot stars, planetary nebulae and bright galaxies. UVSTAR consists of a pair of telescopes and concave grating spectrographs that cover the overlapping spectral ranges of 500-900 and 850-1250 angstrom. The telescopes use two 30 cm diameter off-axis paraboloids having focal length of 1.5 m. An image of the target is formed at the entrance slits of the two concave grating spectrographs. The gratings provide dispersion and re-image the slits at the detectors, intensified CCDs. The readout format of the detectors can be chosen by computer, and three slit widths are selectable to adapt the instrument to specific tasks. UVSTAR has internal gimbals which allow rotation of +/- 3 degree(s) about each of two axes. Dedicated finding and tracking telescopes will acquire and track the target after rough pointing is achieved by orienting the Orbiter. Responsibilities for implementation and utilization of UVSTAR are shared by groups in Italy and the U.S. The first of the five approved UVSTAR flights is scheduled on May 1995.

We have fabricated a device consisting of nine arrays of series- connected superconducting aluminum tunnel junctions on a thin sapphire substrate, as a detector of 6-keV X-rays. Tunnel junctions are of interest as particle detectors because their theoretical minimum excitation energy is on the order of one milli-electron volt, a factor of one thousand lower than conventional semiconductor detectors. We have experimented with a new SiN passivation layer, intended to prevent further oxidation of the tunnel barrier on exposure to air. Preliminary tests with 200 angstrom thick SiN layers indicate improved stability of junction resistance on exposure to air. We will present results from a device with a 400 angstrom thick passivation layer. We will also report on tests of a detector without a SiN layer, where we observed coincident pulses between two of the nine arrays. The energy resolution for 6-keV X-rays is about 1 keV, limited by noise. If the signal size can be increased, pulse height and timing information from the nine separate arrays of this detector should allow simultaneous determination of position and energy.

We have developed microcalorimeters for high resolution soft X- ray spectroscopy that achieve an energy resolution of approximately eV FWHM. An adiabatic demagnetization refrigerator system has been constructed that will survive a sounding rocket launch and maintain the required 60 mK operating temperature following the approximately 17 g rms vibration associated with powered flight. Results of vibration tests show that both mechanical and thermal performance readily meet the requirement for using these detectors successfully on sounding rocket flights. The first flight of this system is intended to produce a high resolution spectrum of the 0.1-1.0 keV diffuse X-ray background, integrated over a approximately 1 steradian field of view. The same cryostat and detector system (36-pixel array) can be flown at the focus of a conical foil imaging mirror to do spatially resolved spectroscopy of supernova remnants and other extended source on future flights.

We are preparing an experimental search for weakly interacting massive particle (WIMP) dark matter using cryogenic germanium detectors. These detectors measure both the ionization and phonons produced by particle interactions in the substrate. The ionization measurement uses low drift fields, approximately equals 1 V/cm. The phonon measurement is made using neutron transmutation doped (NTD) germanium thermistors. Simultaneous detection of phonons and ionization allows us to discriminate between electron-recoil and nuclear-recoil events which gives a powerful method for isolating possible WIMP events (nuclear recoils) from background gamma ray events (electron recoils). Recent work on our understanding and optimization of these detectors will be presented.

Superconducting tunnel junctions have the potential to serve as high-resolution, high-efficiency x-ray detectors for astrophysical and industrial applications. When irradiated by X rays, each X ray excites over 10⁶ charge carriers which cause the detector to generate a pulse of current. We present an analysis of pulse shapes from detectors we have constructed and operated. We fit the decay of the current pulse to a simple model that considers two classes of carrier loss. One model considers only the normal recombination of the charge carriers with themselves, the other included additional losses due to recombination sites within the detector medium. We found that both mechanisms must be taken into account. We also found a small variation in pulse shape depending on which layer of the tunnel junction absorbed the X ray. We expect that this analysis will be a useful tool in comparing different detector designs and operating conditions.

We are building a new type of hard X-ray detector (35-300 keV) for astronomical observations, a high pressure (20 atmospheres) imaging xenon gas scintillation drift chamber. This detector combines the concepts of the gas scintillation chamber and the time projection chamber, utilizing waveshifting fibers to read out the scintillation light. This detector will be the focal plane instrument of the Scintillation Imaging Gas-filled Hard X- ray Telescope (SIGHT), a balloon-borne instrument which promises to combine high sensitivity (2.2 x 10^{-5 (gamma} /cm²sec for narrow lines and 4 x 10^{-6 (gamma} /cm²sec/keV continuum at 70 keV), very good energy resolution (2.6% FWHM 122 keV), and outstanding imaging (1.5 arcminute map pixels). We summarize the capabilities of SIGHT and present recent technical innovations and construction status of the detector.

X-ray calibration of the Electro-Optical Breadboard Model (EOBB) of the XMM Reflection Grating Spectrometer has been carried out at the Panter test facility in Germany. The EOBB prototype optics consisted of a four-shell grazing incidence mirror module followed by an array of eight reflection gratings. The dispersed x-rays were detected by an array of three CCDs. Line profile and efficiency measurements were made at several energies, orders, and geometric configurations for individual gratings and for the grating array as a whole. The x-ray measurements verified that the grating mounting method would meet the stringent tolerances necessary for the flight instrument. Post EOBB metrology of the individual gratings and their mountings confirmed the precision of the grating boxes' fabrication. Examination of the individual grating surface's at micron resolution revealed the cause of anomalously wide line profiles to be scattering due to the crazing of the replica's surface.

The high pressure xenon ionization chamber was designed for measurements gamma-ray lines from cosmic sources. This chamber was installed on board of the orbital station 'MIR' and the measurements are carried out. The 1 liter's chamber was filled with 0.6 g/cm³ density xenon. The energy resolution is 3% FWHM at energy 1 MeV. This experiment has been lasting for about four years on board of the heavy orbital station. Measured background gamma-ray spectra are presented. The background gamma- ray flux is mostly generated by interaction of cosmic rays with the vessel mass. A considerable abundance in energy region 170- 260 keV was registered. This abundance is produced by the radioactive source located in uranium shield on board of transport spacecraft. Also the 511 keV annihilation line was observed. Its intensity has obvious latitude dependence. Therefore it is generated by interaction of cosmic ray with the vessel matter. The strong gamma background decreases significantly the instrument sensibility to gamma-ray bursts.

We are developing Si-implanted thermistors to realize high resolution microcalorimeters. We plan to use these devices in an experiment for the determination of the neutrino mass. The measure implies the evaluation of the correct end-point energy of a beta spectrum with a calorimetric approach. Our study is devoted to outline the optimum fabrication process concerning performances and reproducibility. For such reasons we have realized Si thermistors with different concentration of dopant impurities and with different implant geometries. Tests are performed between 4.2 and 1.2 K using a pumped helium cryostat, and selected samples are characterized at very low temperatures in a dilution refrigerator. Good reproducibility of the devices is necessary for producing an array of detectors. At the same time suitable electronics are developed to optimize the detectors preamplifiers link: minimization of the parasitic capacitance is necessary to reduce the integration of signal and to maximize the speed response of the detector.

We present data from a charge-coupled device (CCD), collaboratively designed by PSU/JPL/Loral, which incorporates several novel features that make it well suited for soft X-ray spectroscopy. It is a three-phase, front-side illuminated device with 1024x1024 pixels. Each pixel is 18 microns by 18 microns.The device has four output amplifiers: two conventional floating diffusion amplifiers (FDAs) and two floating gate amplifiers (FGAs). The FGA non-destructively samples the output charge, allowing the charge in each pixel to be measured multiple times. The readnoise of a given pixel is reduced as the square root of the number of readouts, allowing one to reduce the amplifier noise of these devices to well below the 1/f knee. We have been able to achieve sub-electron readnoise performance with the floating gate amplifier (0.9 e+-) rms with 16 reads per pixel). Using the FGA, the measured energy resolution at 5.9 keV is 120 eV (FWHM). The CCD also has a thin poly gate structure to maximize soft X-ray quantum efficiency. Two-thirds of the active area of the chip is covered only by an insulating layer (1000 angstrom) and a thin poly silicon electrode (400 angstrom). This design enhances the soft X-ray quantum efficiency, but retains the excellent charge transfer efficiency and soft X-ray charge collection efficiency of front-side illuminated devices. The measured energy resolution at 277 eV is 38 eV (FWHM) with a measured quantum efficiency of 15%. We also show that this device performs well below 100 eV, as demonstrated by the detection of Al L fluorescence at 72 eV with a measured FWHM of 16 eV.

In this paper we investigate the QP transport and loss mechanisms in a superconducting tunnel junction using the Low Temperature Scanning Electron Microscopy (LTSEM) technique. This approach allows precise control of the energy and position of a deposited electron pulse, which, within certain conditions, simulates the X-ray photo-absorption process. An Nb-Al-AlO_xNb junction designed as a test structure which included Al blocks in the leads to act as quasiparticle traps, has been investigated. Asymmetries in the LTSEM signal distribution can be qualitatively described from the device geometry. From both the spatial distribution can be qualitatively described from the device geometry. From both the spatial distribution and the time resolved measurements the diffusion length in the amorphous Nb was determined to be of the order of 8 micrometers . The LTSEM technique has demonstrated that quasiparticles produced in the leads cannot enter the tunnel barrier due to the presence of the Al traps.

The Advanced X-ray Astrophysics Facility (AXAF) is one of NASA's 'great observatories' (launch 1998). One of its two focal plane detectors is the High Resolution Camera (HRC) assembly consisting of two microchannel Plate (MCP) based detectors. Key components of the two HRC detectors are UV/Ion shields consisting of metalized sub-micron plastic membranes, designed to prevent UV light and positive ions from reaching the detectors' sensitive surfaces. We discuss results from transmission measurements that have been conducted at the National Synchrotron Light Source (NSLS), on sample plastic membranes and the baseline design HRC-I UV/Ion shield.