An extreme ultra-violet diffuse spectrograph known as the ultraviolet cosmic background spectrometer is scheduled for a 1996 launch on the NASA SSTI mission Lewis. UCB is one of three prime science instruments aboard the Lewis spacecraft and is schedules to conduct observations for 3 to 5 years. The spectrograph will obtain spectra of diffuse 550 to 1100 angstrom radiation with a sensitivity improvement of an order of magnitude or more in comparison with previous work. UCB incorporates new technology such as a special diffraction grating, an anti-coincidence guarded micro- channel plate detector system, low-radioactivity ultra low- noise micro-channel plates, and a chemical treatment for enhancing detector efficiency. The observations will contribute important new information about the Galaxy's local interstellar medium and about speculative scenarios regarding exotic nuclear particles in dark matter. We describe the instrumentation and the UCB science mission.

The low energy concentrator system (LECS) is an imaging x- ray spectrometer. I is one of the narrow field instruments onboard the SAX satellite and covers the energy range from 0.1 to 10 keV. The good low energy response of the detector is achieved by using a driftless gas cell and a thin multilayer polyimide foil as an entrance window. SAX was launched on April 30, 1996. Following a two month commissioning phase, the satellite has entered the science verification phase. We report here on the first in-flight data acquired with the LECS. Using back-ground measurements and well known x-ray sources, we present the first results of the in-orbit performance and calibrations an compare them to ground measurements acquired at synchrotron and long beam x-ray sources. After a brief description of the instrument we discuss some aspects related to the ground calibrations. I particular the entrance window characteristics and the particularities of a driftless detector design are reviewed. By correcting for the x-ray absorption depth, we also show how the energy resolution could be enhanced.

We describe methods used to measure the x-ray detection efficiency of reference CCDs for the AXAF CCD imaging spectrometer in the spectral range between 2 keV and 10 keV. The reference CCDs are identical to and are used as calibration transfer standards for the actual flight CCDs. Both radioactive (⁵⁵Fe) and fluorescent x-ray sources are used to illuminate the CCDs, providing a range of discrete emission lines to cover the energy band. A Si(Li) solid state detector is inserted into the beam to provide absolute calibration from 2 - 10 keV [where the Si(Li) detection efficiency can be calculated from first principles]. The response function of the Si(Li) detector is discussed, along with factors used to obtain CCD efficiency parameters from the raw data. Calibration geometry and typical data are also presented.

Results of the first CCD observations of the x-ray background between 0.2 and 10 keV are presented. Data were obtained from individual sounding rocket flights on May 22, 1995 from White Sands, New Mexico and on October 25, 1995 from Woomera, Australia. The target for the second flight was a bright region of the 3/4 keV x-ray background centered at 0 degree longitude and minus 15 degrees latitude in galactic coordinates. Covering approximately 1800 square degrees, this feature dominates all-sky surveys below the galactic plane from 0.5 to 1.5 keV. This data is compared with data from a dim region of the 3/4 keV x-ray background in the constellation Draco, obtained on the first flight. The detector for these flights was a thin gate CCD built by EEV and designed to maximize x-ray response below 0.75 keV without adopting a backside illumination scheme. Improved quantum efficiency over conventional x-ray CCDs above 1 keV was also achieved due to the high resistivity (1500 ohm-cm) of this device. This type of CCD was flown on the CUBIC experiment in November 1996. Similar devices are also scheduled to be launched on Leicester University's spectrum X/JET-X and XMM/EPIC instruments.

The cosmic unresolved background instrument using CCDs (CUBIC) was scheduled for launch on the Argentine/U.S. SAC-B satellite in October 1996. This instrument is designed to perform moderate resolution nondispersive x-ray spectroscopy of the diffuse x-ray background over the band 0.2 - 10.0 keV using state-of-the-art photon-counting CCDs. The instrument is optimized for spectroscopy of diffuse emission with a field of view approximately 5 degrees multiplied by 5 degrees below 1 keV and 10 degrees multiplied by 10 degrees above 3 keV. Here we discuss the present state of analysis of our preflight calibration data and present preliminary operational plans.

The proportional counter array (PCA) is designed to perform microsecond timing of bright galactic sources and broad band, confusion limited, studies of faint extragalactic sources in the 2 - 60 keV x-ray band. The PCA was launched as part of the Rossi X-ray Timing Explorer (RXTE) satellite into a circular orbit of altitude 580 km and 23 degrees inclination on December 30, 1995. The mission contains three experiments: a set of large area xenon proportional counters sensitive from 2 - 60 keV (proportional counter array: PCA), a set of large area sodium iodide scintillators sensitive from 15 - 200 keV (high energy x-ray timing experiment: HEXTE), and three wide field of view scanning detectors which monitor most of the sky each orbit (all sky monitor: ASM). The goals of the mission are summarized by Swank et al. We present performance and calibration data on the measured and predicted in-orbit background, energy response, relative and absolute timing performance, and the operational possibilities made available with the high performance experiment data system (EDS) designed and built by MIT.

Microchannel plates (MCPs) are solid state electron multipliers consisting of millions (10E5 - 10E7 channels/cm²) of microscopic (typically 10 - 25 microns) continuous dynode electron multipliers all fused together in a solid array. Fabricated from an alkali doped, reduced lead silicate glass, microchannel plates are known as excellent high gain, low noise, two dimensional detectors of charged particles and electromagnetic radiation. The microchannel plate manufacturing process begins with a series of glass fiber draws in which an acid soluble core glass is combined with an alkali soluble clad tube and drawn to form a mono fiber. Mono fibers (typically 2,000 to 4,000) are then assembled into a hexagonal preform called a multi wrap. The preform is again drawn to form a multifiber producing an overall feature size reduction of typically 2000:1. The multi fibers then become the basic building blocks. Hundreds of multi fibers are next arranged to form the active area of the MCP. High temperature vacuum fusion is then used to fuse the multi fibers together with the solid glass border (if used) to form a billet or boule. Standard semiconductor slicing, lapping and polishing techniques are used to prepare the wafers for chemical processing. Chemical processing consists of etching open the microchannels, adjusting the open area ratio (OAR) and preparing the silica rich emissive layer. A hydrogen firing is used to reduce the lead glass making it electrically conductive. Finally a thin (typically 2,000 to 3,000 angstroms) film of metalization is vacuum deposited on both sides of the microchannel plate to electrically connect each of the channels in parallel, therefore ensuring the same potential is applied to each channel. Microchannel plates operate on the principle of secondary electron emission. In operation primary events enter the input side of the MCP and collide with the channel wall. If the primary event has sufficient energy, secondary electrons will result. The resultant secondary electrons will be accelerated down the channel by the electric field produced when a high voltage is applied between the electrode faces. Additional collisions with the channel walls produce still further secondary electrons.

Reducing plate resistance is one of the possible ways to increase the count rate capability of microchannel plates (MCPs). Bonding a low-resistance plate to a cooled substrate provides a conductive path for heat transport an prevents thermal runaway. MCPs of very low resistance (less than or equal to 500 k(Omega) ), bonded to a Peltier cooler, were tested using different bonding techniques. Stable, reproducible operation of a rear-cooled MCP (60:1, 10 micrometer channels) was achieved for biases up to 1320 volts (R_MCP equals 260 k(Omega) at that voltage), when the MCP bias current was as high as 5.1 mA and the heat generated by the plate was 0.78 W cm^-2. The count rate reached the value of 10⁸ cm^-2s^-1 limited not by the plate recharge time, but by the intensity of the mercury vapor UV lamp (2540 angstrom) used for illumination. The dark noise, at the same time, was less than 1 cm^-2s^-1. A thermal model of such conductively cooled MCPs is described. The count rate characteristic of a microchannel plate is well-known to depend on the pattern of illumination. This paper updates our previous investigation of radial gain depression in the vicinity of high count rate point-like illumination.

Small pore size microchannel plates (MCPs) are needed to satisfy the requirements for future high resolution small and large format detectors for astronomy. MCPs with pore sizes in the range 5 micrometer to 8 micrometer are now being manufactured, but they are of limited availability and are of small size. We have obtained sets of Galileo 8 micrometer and 6.5 micrometer MCPs, and Philips 6 micrometer and 7 micrometer pore MCPs, and compared them to our larger pore MCP Z stacks. We have tested back to back MCP stacks of four of these MCPs and achieved gains greater than 2 multiplied by 10⁷ with pulse height distributions of less than 40 percent FWHM, and background rates of less than 0.3 events sec^-1 cm^-2. Local counting rates up to approximately equals 100 events/pore/sec have been attained with little drop of the MCP gain. The bare MCP quantum efficiencies are somewhat lower than those expected, however. Flat field images are characterized by an absence of MCP fixed pattern noise.

The AXAF-HRC UV/ion shields have to provide high UV rejection from diffuse background and bright UV sources (e.g. rejection greater than 10⁷ at wavelength longer than approximately 300 angstrom for the HRC-I). In the framework of the AXAF-HRC calibration program we have conducted UV (300 - 2500 angstrom) and FUV/visible (1900 - 10,000 angstrom) transmission measurements on the baseline design UV/ion shields based on Lexan and aluminum. The results of these measurements, here reported, have shown that the baseline design UV/ion shields did not meet the scientific requirements of UV opacity and as a consequence, the UV/ion shields were redesigned. UV tests of new UV/ion shields, based on new materials, is in progress.

High spectral resolution x-ray transmission measurements in the energy range 60 - 1950 eV have been conducted at BESSY 1 synchrotron (Berlin) on samples of aluminum coated Lexan in order to define an accurate model of x-ray absorption near edge structures for the AXAF-HRC UV/ion shields material. A large number of energies have been surveyed with a spectral resolution ranging from E/(Delta) E equals 2500 at 100 eV to E/(Delta) E equals 700 at Al-K edge. The spatial variations of such absorption structures also have been investigated surveying different positions of the film samples.

X-ray transmission measurements have been conducted at the XACT facility on baseline design AXAF-HRC UV/ion shield using an electron impact x-ray source, a transmission grating monochromator and gas flow proportional counters. Transmission has been measured at several energies in the range 0.1 - 2.0 keV with and without the transmission grating monochromator. It turns out that the monochromator enormously improves the measurement accuracy. UV measurements conducted by us on the same shield and reported elsewhere showed an unexpectedly high UV transmission which led to a redesign of the UV/ion shields. Calibration of the new shields, based on different materials, is still in progress. In this paper we outline the calibration procedure and the data analysis technique, and report transmission results on the baseline design shield.

We describe the equipment and the experimental set-up at the XACT facility -- Osservatorio Astronomico di Palermo G.S. Vaiana, employed in the calibration of the AXAF-HRC UV/ion shield. The facility has been expanded to improve its performance and to extend its bandpass to UV wavelengths. It now covers the 2550 - 1 angstrom wavelength range, is equipped with an advanced micropositioning system, has imaging capabilities in the wavelength range 1200 - 1 angstrom. The test chamber now opens to a class 1000 clean room which, along with the oil-free pumping system, makes cleanliness one of the characteristics of the facility

Accurate quantum efficiency calibrations for CCDs require stable sources of known x-ray energies. Radioactive sources are the most stable although some stable commercial x-ray tubes are available. However, sealed, stable x-ray tubes include windows which filter low energy x-rays to which our CCDs are sensitive. Therefore we have developed a windowless radioactive source using the beta spectrum from tritium to fluoresce low-energy x-rays from low Z targets. The potential drawback of tritium outgassing is also investigated. This source is coupled with an additional system based on a stable commercial x-ray tube to produce higher energy x-rays. Together these sources form a system for comparative quantum efficiency measurements with two CCDs mounted on translation stages. We report on the physics and development of these x-ray sources.

We summarize the strategy and techniques used to calibrate x-ray CCD detectors for the AXAF CCD imaging spectrometer in the spectral range between 0.2 keV and 10 keV. The very demanding calibration requirements (energy scale knowledge error of order 0.1%; detection efficiency knowledge error of order 1%) are reviewed. The primary standards chosen for the calibration are discussed, with particular attention to the use of undispersed synchrotron radiation as a primary radiometric standard for the detection efficiency calibration. We review the basic models of the detector response which it is the objective of the calibration enterprise to constrain. The accuracy and reproducibility of the energy scale, spectral redistribution and detection efficiency calibration is discussed and illustrated with sample results from calibration of flight detectors.

As part of our program to select and calibrate flight- quality, x-ray CCD detectors for the AXAF CCD imaging spectrometer, we have developed efficient detector screening methods. Our screening protocol, which measures device-level performance parameters (including noise, dark current and charge transfer efficiency) as well as x-ray spectral resolution in the 0.3 - 6 keV band, allows us quickly to identify which of the greater than 30 flight candidate detectors warrant the expenditure of severely limited time available for calibration. The performance criteria used to rank devices are discussed, and the details of the measurement methods are presented. Summary results of the screening measurements are presented for a large sample of devices, and detailed data on selected devices are described. We find that the performance variations among the sample of flight devices to be relatively small but significant.

We discuss the current status of the Advanced X-ray Astrophysics Facility (AXAF) High Resolution Camera (HRC) quantum efficiency (QE) calibration. The absolute quantum efficiency of flight candidate, CsI coated HRC microchannel plates (MCPs) for the imaging detector (HRC-I) manufactured by Galileo Electro-Optics Corporation (GEOC) has been measured at several energies. We find the absolute QE of these MCPs (measured at SAO) to be 0.41 at C K_alpha (E equals 277 eV) and 0.28 at Al K_alpha (E equals 1487) eV). The absolute QE of flight-like HRC-I MCPs manufactured by Phillips Components (measured at the University of Leicester) is approximately 0.40 at both C K_alpha and Si K_alpha (E equals 1739 eV). We are now in the process of measuring the absolute QE of both the HRC-I and HRC-S flight detectors at 22 different energies at 4 azimuthal and 5 polar angles. A summary of planned measurements is presented. In addition, we present data taken at the Daresbury Synchrotron Radiation Source to map out the detailed edge structure of the MCP glass and coatings. In particular, we present measurements of the relative QE of CsI coated MCPs around Cs and I M edges, and absolute measurements around the K K and Cs L_III edges. The absolute measurements of the flight instrument at the 22 discrete energies will be combined with the relative synchrotron measurements of flight-like detectors to produce the absolute QE of the HRC over the entire AXAF bandpass (0.1 to 10 keV).

The Advanced X-ray Astrophysics Facility (AXAF) is scheduled for launch in summer/fall 1998. One of its two focal plane instruments is the high resolution camera (HRC). The HRC consists of two detectors; an imaging detector (HRC-I) and a detector (HRC-S) for the spectroscopic read-out of the low energy transmission grating (LETG). Both detectors are comprised of a chevron pair of microchannel plates with a crossed grid charge detector (CGCD) and a UV/ion shield (UVIS). Each UVIS is mounted as a free standing window in front of the MCPs. The HRC-I UVIS is 10 cm multiplied by 10 cm and consists of 5000 angstrom polyimide, one side of which is coated with 700 angstrom aluminum. The other side is coated with 200 angstroms of carbon. The HRC-S UVIS consists of three 3 cm multiplied by 10 cm segments. The thickness of the polyimide film (2000 - 2500 angstrom) and of the aluminum coating (300 - 2000 angstrom) of each segment has been varied to optimize the shield's performance with the LETG. In this paper, x-ray transmission models are presented. Results of laboratory x-ray transmission measurements of the flight HRC-I UVIS at various energies in the range of 0.1 to 1.5 keV, as well as results of x-ray transmission measurements of a flight UVIS-I witness sample, are discussed. Results of UV transmission measurements of a flight UVIS-I witness sample also are presented.

A new method of x-ray polarimetry based on the photoeffect in a finely segmented silicon charge coupled device (CCD) first proposed by G. W. Fraser has been confirmed using monochromatic synchrotron radiation and planar channeling radiation. For the smallest pixel dimensions (6.8 multiplied by 6.8 micrometer squared) available today in commercial optical CCD cameras an analyzing power for linear polarization in the order of 10% has been measured at energies above 10 keV. The strong energy dependence of the analyzing power has been measured in the energy range from 9 - 100 keV and is compared to expectations from detailed MC simulations. In addition to events due to photoeffect in the thin depleted front layer of the CCD also diffusion spread events resulting from much more abundant conversions deeper inside the chip were found to be very useful for simultaneous measurements of polarization, energy and position with sub-pixel accuracy (0.9 micrometer rms at 15 keV). For the first time we have now made use of the CCD polarimeter for the measurement of the linear polarization of parametric x-rays (PXR), i.e. radiation which is coherently generated by charged particles traversing a crystal.

We describe the instrumental apparatus developed at the Catania Astrophysical Observatory to characterize the CCDs detectors for the 'spectrum UV' space observatory. The system allows us to perform a full characterization of the electro-optical properties of CCDs. In particular the system is designed to measure the CCDs quantum efficiency (QE) in the wavelength range 1300 - 11000 angstrom. The main components of the instrumental apparatus are a deuterium and a xenon lamp as radiation sources, a monochromator as light disperser, a series of filters to minimize the contribution of the straylight and the second order of the gratings and a series of NIST calibrated photodiodes as reference detectors. For measurements below 2000 angstrom the system is operated under vacuum conditions. The short wavelength cutoff is due to the use of MGF₂ optics. The CCDs are operated using different CCD controllers, one developed for the Catania Astrophysical Observatory and the other one for the Italian National telescope 'Galileo.' Here we report on the performances of the instrumental apparatus and also present results on the QE of a CCD chip manufactured by EEV.

We studied the proton damage effects of the x-ray CCD. We have measured x-ray CCD performances after the irradiation of energies at 2 and 9.5 MeV, and confirmed clear degradation of charge transfer efficiency (CTE) and the energy resolution. To recover degraded CTE and the energy resolution, we tried the charge injection technique, and found the improvement of CTI and the energy resolution to be one-quarter and one-third, respectively. We also estimated the energy level of the deep trap, which causes the quantization of the dark current from the radiation-damaged pixels. The trap energy level is about 0.57 eV, or near the center of forbidden band.

X-ray CCDs developed at MIT Lincoln Laboratories for the AXAF CCD Imaging Spectrometer (ACIS) have been calibrated in the 0.25 - 1.5 keV spectral range using an erect-field grating spectrometer and an electron impact x-ray source in our laboratory. A combination of the spectrometer with an x- ray CCD on high resistivity substrate allows efficient order separation, and measurement of the CCD energy scale and spectral response function as essentially continuous functions of energy over the spectrometer passband. The CCD energy scale is found to be linear to approximately 0.5% in this spectral band. Relative variations in the detection efficiency of the CCD can also be studied with this system. A near edge structure is detected in the CCD response around the oxygen K absorption edge. Comparison of these results with the data acquired with a synchrotron radiation source and monochromator confirms that these structures are features of the detector response. The edge structure allows us to measure the absolute dispersion relation of the spectrometer (and hence the zero-point of the CCD energy scale) with a precision better than 1 eV. We also detect considerable structure in characteristic nitrogen and oxygen emission lines from the electron impact source. We discuss likely mechanisms for the production of this structure.

A new concept, compact and vacuum compatible CCD camera has been developed for application in the extreme ultraviolet and soft x-ray (XUV) spectroscopy. The main features of this detector are a 'remote cooling' system, the possibility to locate the same CCD camera on the Rowland circle of spectrometers having a normal or grazing incidence configuration, a compact and lightweight package, the vacuum compatibility and the compatibility with two CCD sensors, available for applications in the spectral region of interest (10 divided by 800 angstrom). The 'remote cooling' means a themoelectric cooler placed on the spectrometer wall, connected to the CCD camera by means of a 35 cm long, flexible thermal conductor allowing a minus 40 degree Celsius operative temperature of the sensor. The bidimensional capabilities of the CCD, in conjunction with the stigmaticity of the toroidal grating used as dispersing element inside the normal incidence spectrograph allow both spectral and spatial resolutions on the light source. THe first observation performed by this detector concerns the EUV spectrum of an aluminum laser produced plasma and it is presented here.

A novel form of thin-coated transparent polymer film undergoes a radiation-initiated solid-state polymerization reaction when irradiated with deep ultraviolet and x and gamma rays. It forms a permanent deep-blue high-resolution image, without the need for chemical, optical, or thermal processing. The increase in the optical density with absorbed dose, irradiance or photon fluence is a linear function with relatively high contrast and without appreciable reciprocity failure and has the same response in vacuum and in air. The sensor coating thickness on a polyester base is approximately 6 micrometer. It forms the radiation-induced image that can resolve 600 line pairs per millimeter. The ultraviolet sensitivity at 266 nm wavelength is such that the optical density produced by an irradiance of 30 mJ/cm² is approximately 1.00 at the wavelength maximum of the absorption spectrum (670 nm). UV, low-energy x-ray (10 keV) and gamma-ray (660 keV) response characteristics are presented, which demonstrate the ability to evaluate and map radiation image distributions quantitatively. The films are useful to calibrate beam profiles, including the penumbra shapes, because of the wide dynamic range and linear response.

A novel fiber optic sensor responds with a supra-linear relationship between optical density readout and absorbed dose, when irradiated with high doses of x and gamma radiation (10^-2 to 10⁴ Gy). The radiation sensor medium is a radiochromic gel core filling a flexible fluorinated polyethylene plastic tubing that is fitted with either Suprasil quartz plugs as radiation-insensitive end windows or Pyrex glass beads that serve as lenses. Readings are made with a specially designed spectrophotometer enabling efficient propagation of interrogating light with a narrow band-pass filter at the optical wavelength of the radiation-induced color absorption band maximum (600 nm). The absorption at 600 nm is related to the formation of a highly conjugated carbocationic dye. The formation of the conjugation proceeds through very fast kinetics (approximately 1 ns) followed by relatively slower kinetics (2 ms). The shortest selective fiber optic sensor length is 5 cm and outer diameter is 0.27 cm, allowing selective placement of the sensor portion into remote irradiated components. Fiber optic sensor lengths up to 150 cm allow dose measurements as low as 10 ^-2 Gy. Extraction of radiation dosimetry data to the external reader is carried out either in real-time or on demand following irradiation, and is made possible by connecting the sensor length to ancillary fiber optic access loop.

Soft x-ray detectors for astronomical applications are often also sensitive to visible and UV photons. Filters of a new design have been developed, which could be used in future missions to suppress the flooding of x-ray detectors by low energy photons. Three series of filters are discussed: aluminum/silicon multilayers, Niobium and calcium/boron multilayers. The filters are typically 100 to 200 nm thick and reject the IR/visible/UV from 10^-4 to 10^-6. The transmission for soft x-rays is above 10% for wavelengths less than 30 nm, when combining the bandpasses of at least two filters. The optimum transmission band depends very much on the filter type. The IR/visible/UV has been measured using standard laboratory spectro- photometers while the x-ray transmission characteristics have been determined using synchrotron radiation.

On future astronomical instruments for the soft x-ray to FUV, stray light may be a significant cause of background events. Currently, we are engaged in an ongoing program to identify materials that are suitable for use as low- reflectance surfaces in space based instruments. As a result, we have measured the scattering performance in this spectral region, of wide a selection of low-reflectivity materials, produced with a range of processes. We present preliminary measurements of the absolute bidirectional reflectance distribution function (BRDF) for a selection of seven of these materials. Measurements were obtained at a five spectral lines, including strong geocoronal lines, over the wavelength range 44 to 1216 angstrom at near grazing incidence. We find that in most cases for constant incident and scatter angles, the total variation of BRDF with wavelength over this range is only a factor of order ten. We also find that although we have identified materials which in many instances have lower reflectances than bead blasted aluminum, it is still a good choice for most applications given its low cost and convenience.

Fourier telescopes are an effective approach for providing images of hard x-ray and gamma-ray sources found in the sky. Sufficient coverage of the (u,v) plane is a requirement for effective imaging. Unfortunately, this requirement is diametrically opposed to the requirements to minimize instrument weight and cost which translate into minimizing the number of grids. This paper reports on a telescope design incorporating only one real and imaginary set of grid pairs which provides superior imaging performance at a significantly reduced cost.

The reflection grating spectrometer (RGS) on-board the x-ray multi-mirror (XMM) mission incorporates an array of reflection gratings oriented at grazing incidence in the x- ray optical path immediately behind a grazing incidence telescope. Dispersed light is imaged on a strip of CCD- detectors slightly offset from the telescope focal plane. The grating array picks off roughly half the light emanating from the telescope; the other half passes undeflected through the array where it is imaged by the European photon imaging camera (EPIC) experiment. XMM carries two such identical units, plus a third telescope with an EPIC detector, but no RGS. The basic elements of the RGA include: 202 identical reflection gratings, a set of precision rails with bosses that determine the position and alignment of each grating, a monolithic beryllium integrating structure on which the rails are mounted, and a set of three, kinematic support mounts which fix the array to the telescope. In this paper, we review our progress on the fabrication and testing of the RGA hardware, with particular attention to the components comprising the engineering qualification model, a flight-representative prototype which will be completely assembled in September of this year.

The x-ray multi-mirror mission (XMM) is the second cornerstone mission of the ESA Horizon 2000 Science Programme. When launched in late 1999 it will provide a world-class observatory facility for x-tray astronomers. This paper describes the overall concept of the mission, including the spacecraft bus, the instruments and the innovative replicated optics that produce images of better than 20 arcsecs half energy width, and a total geometric collection area of more than 4500 cm². The observatory is unique in that it will provide simultaneously, high throughput non-dispersive spectroscopic imaging (EPIC instrument), medium resolution dispersive spectroscopy (reflection grating spectrometer) and optical/UV imaging and timing from a co-aligned instrument (optical monitor). We describe some of the operational aspects and provide a brief description of the scientific potential of the payload.

The x-ray multi mirror mission (XMM) is the second cornerstone mission of the ESA Horizon 2000 Science Programme, to be launched in late 1999. With its three mirror modules, each comprising of 58 concentric grazing incidence mirrors, it will provide unprecedented effective area for x-ray astronomy. Three x-ray CCD cameras and two reflection grating spectrometers will be positioned in the focal plane to collect the photons and generate the scientific data. Additionally, an optical monitor will provide optical and UV imaging and timing information, simultaneously to the x-ray measurements. This paper introduces the mission objectives and elaborates the driving requirements for the spacecraft and the resulting configuration and system design. The focal length of 7.5 m creates a tall spacecraft with the mirrors on one end and the instruments on the other end, connected by a thin walled tube. This drives design choices in may areas, such as structure, thermal and test concept. The required imaging and spectroscopy accuracy leads to highly stable design solutions for the telescope tube and the mirrors and instrument platforms as well as for the attitude control. The spacecraft subsystems are described and several key system aspects are highlighted, including design aspects related to contamination control and minimization of stray light.

The x-ray multi-mirror mission is one of the four 'cornerstone' projects in the ESA Long-Term Program for Space Science. A vertical test facility to assess the optical quality of individual XMM optics and of each of the complete telescopes has been built at the 'Centre Spatial de Liege.' The main feature of this facility is its vertical optical axis in order to avoid earth gravity induced mechanical deformations of the thin optical shells. The originality of the facility is to use an extreme ultra- violet (548 angstrom) full illumination collimated bean (800 mm diameter), to minimize the diffraction effect and obtain image quality of the full aperture; to operate with an x-ray pencil beam to acquire the data of the scattering or surface quality of the mirrors; and finally, to work with a partial illumination collimated x-ray beam to measure the image quality of a sector. After description of the vertical test facility, the alignment of the optical stimuli and the overall performance of the facility are presented and discussed. These performance are controlled with a demonstration model of an XMM mirror module.

The high throughput x-ray spectroscopy mission XMM is 'cornerstone' project in the ESA Long Term Programme for Space Science. This observatory has at its heart three heavily nested Wolter 1 grazing incidence x-ray telescopes which will provide a large collecting area (1,600 cm² each at 1.5 keV). This optical system has a spatial resolution of 2 - 30 arcsec and when coupled with reflection grating spectrometers and x-ray CCD cameras, it will provide a major advance in astrophysics by the end of the century. In this paper, we first present the design of the telescope and then describe the manufacturing and the integration processes of the telescope with the emphasis on the production of the x-ray mirrors. We then concentrate on the technical problems and the solutions found for the production of these mirrors. Last but not least, the results achieved on the qualification model of the XMM telescope are also presented.

The high throughput x-ray spectroscopy mission (XMM) is a 'cornerstone' project in the ESA Long-Term Programme for Space Science. The satellite observatory uses three grazing incidence mirror modules coupled to reflection grating spectrometers and x-ray CCD cameras. In order to achieve a large effective area, each XMM mirror module consists of 58 Wolter I mirrors which are nested in a coaxial and cofocal configuration. Each mirror shell is characterized by detailed metrology before further integration into the mirror modules. The present paper describes the mirror metrology and the way metrology data will be used to simulate the mirror performance. Simulation results are compared with x-ray images.

The high throughput x-ray spectroscopy mission (XMM) is a 'cornerstone' project in the ESA Long-Term Programme for Space Science. The satellite observatory uses three grazing incidence mirror modules coupled to reflection grating spectrometers and x-ray CCD cameras. In order to achieve a large effective area, each XMM mirror module consists of 58 Wolter I mirrors which are nested in a coaxial and cofocal configuration, in 1995-96, a qualification model of an XMM mirror module which includes a representative number of mirror shells was manufactured. This model was sent to the CSL and PANTER facilities for UV and x-ray testing. The present paper describes the results of the pre-environmental tests performed at these facilities.

The European photon imaging camera (EPIC) is one of the two main instruments onboard the ESA X-Ray Cornerstone Mission XMM. It is devoted to performing imaging and spectroscopy of the x-ray sky in the domain 0.1 10 keV with a peak sensitivity in 10⁵ seconds of 2 multiplied by 10^-15 erg/cm^-2. The x-ray instrumentation is complemented by a radiation monitor which will measure the particle background. The spectral resolution is approximately 140 eV at 6.4 keV and 60 eV at 1 keV. The instrumentation consists of three separate focal plane cameras at the focus of the three XMM telescopes, containing CCDs passively cooled to typically minus 100 degrees via radiators pointing toward the anti-Sun direction. The two cameras with the field of view partially occulted by the RGS grating boxes will have MOS technology CCDs while the third camera, with full field of view, will be based on p-n technology. The CCDs in the focal plane of the cameras will cover the entire 30 foot by 30 foot field of view of the telescope while the pixel size (40 by 40 (mu) for the MOS camera and 150 multiplied by 150 (mu) for the p-n) will be adequate to sample the approximately 20' PSF of the mirrors. In order to cope with a wide range of sky background and source luminosity in the visible/UV band, a filter wheel with six positions has been implemented in each camera. The six positions correspond to: open position, closed position, one thin filter (1600 angstrom of plastic support and 400 angstrom of Al), one medium filter (1600 angstrom of plastic support and 800 angstrom of Al) and one thick filter (approximately 3000 angstrom of plastic support, approximately 1000 angstrom of Al and 300 Angstrom of Sn). The final position will be a redundant filter of type still to be decided. A set of radioactive sources in each camera will allow the calibration of the CCDs in any of the operating modes and with any filter wheel position. Vacuum doors and valves operated will allow the operation of other camera heads on the ground, in a vacuum chamber and/or in a controlled atmosphere, and will protect the CCDs from contamination until the spacecraft is safely in orbit. The MOS camera will have 7 CCDs, each of 600 by 600 pixels arranged in a hexagonal pattern with one central and six peripheral. The p-n camera head will have 12 CCDs, each with 200 multiplied by 64 pixels, in a rectangular arrangement, 4 quadrants of 3 CCDs each. The radiation monitor is based on two separate detectors to monitor the low (electrons greater than 30 keV) and the high (electrons greater than 200 keV and protons greater than 10 MeV) energy particles impinging on the telescope along its orbit.

The x-ray astronomy group at the University of Leicester is responsible for the development of two out of three of the focal plane cameras for the EPIC instrument on ESA's cornerstone mission XMM. CCDs are being developed in collaboration with EEV Ltd. of Chelmsford, UK, to perform the imaging spectroscopy at the prime focus of two of the XMM telescopes. The detectors require Fano-limited energy resolution and high detection efficiency over the 0.1 to 15 keV band. Devices are being constructed using high resistivity epitaxial silicon of 80 micrometer thickness, producing deep depletion, with an efficiency at the iron line (6.4 keV) of 75%. The low energy (less than 1 keV) x- ray performance is being maximized in the front-illumination devices by using novel 'open electrode' structures resulting in an efficiency of 25% at carbon-K (277 eV). This paper provides an update on the instrument concept and performance which is now entering the flight model build phase. The test results of the new custom CCD detectors are presented.

We have been developing optical filters for ESA's x-ray astronomy project XMM (x-ray multi mirror mission). Specific CCDs will be used as detectors in the focal plane on board the observatory. Since these detectors are sensitive from the x-ray to the NIR (near infrared) spectral range, x-ray observations require optical filters, which combine a high transparency for photon energies in the soft x-ray region and a high opacity for UV (ultraviolet) and VIS (visible) radiation as well. With respect to the mission goal in orbit three types of flight model filters are designed having different spectral transmittance functions. We report on one of these types, a so-called 'thick' filter, which has been realized within the EQM (electrical qualification model)- phase of the project. The filter features a cut-off in the EUV (extreme ultraviolet) spectral range and suppresses radiation below 10 eV photon energy by more than 8 orders of magnitude. It has an effective aperture of 73 mm without any support structure. A 0.35 micrometer thick polypropylene carrier foil is coated with metallic films of Al and Sn. The manufacturing process, the qualification measurements and the environmental tests are described, and the resulting performance data is presented.

The x-ray multi-mirror (XMM) mission is the second of four cornerstone projects of the ESA long-term program for space science, Horizon 2000. The payload comprises three co- aligned high-throughput, imaging telescopes with a FOV of 30 arcmin and spatial resolution less than 20 arcsec. Imaging CCD-detectors (EPIC) are placed in the focus of each telescope. Behind two of the three telescopes, about half the x-ray light is utilized by the reflection grating spectrometer (RGS). The x-ray instruments are co-aligned and measure simultaneously with an optical monitor (OM). The RGS instruments achieve high spectral resolution and high efficiency in the combined first and second order of diffraction in the wavelength range between 5 and 35 angstrom. The design incorporates an array of reflection gratings placed in the converging beam at the exit from the x-ray telescope. The grating stack diffracts the x-rays to an array of dedicated charge-coupled device (CCD) detectors offset from the telescope focal plane. The cooling of the CCDs is provided through a passive radiator. The design and performance of the instrument are described below.

Back-illuminated CCDs with high quantum efficiency in the soft x-ray range have been developed by EEV in collaboration with the Space Research Organization of the Netherlands (SRON) and the European Space Agency (ESA). These CCDs will be used as detector for the reflection grating spectrometer on board of the ESA x-ray multi-mirror mission XMM. To cover the full image of the reflection grating spectrometer an array of 9 CCDs along the Rowland circle with minimum dead space between the adjacent CCDs is needed. To obtain a high quantum efficiency over the full energy range (0.35 to 2.3 keV) the CCDs are illuminated from the backside. This requires a thin (approximately 50 nm) and homogeneous passivated layer at the backside, which is obtained by gas immersion laser doping. In addition a thin Al layer is deposited on the backside to reduce the sensitivity of the CCDs for visible/UV light. The technical aspects of the production of these CCDs as well as their calibration are discussed.

The optical/UV monitor (OM) on the ESA x-ray cornerstone mission XMM is designed to provide simultaneous optical and UV coverage of x-ray targets viewed by the observatory. The instrument consists of a 30 cm modified Ritchey-Chretien telescope. This feeds a compact photon counting detector operating in the blue part of the optical spectrum and the UV (1600 - 6000 angstrom). The OM has a square field of view of approximately 24 arcmin along the diagonal, and will cover the central region of the field of view of the EPIC x- ray cameras where the x-ray image quality is best. Because of the low sky background in space, the sensitivity of the OM for detecting stars will be comparable to that of a 4-m telescope at the Earth's surface; it should detect a B equals 24th magnitude star in a 1000 s observation using unfiltered light. The pixel size of the detector corresponds to 0.5 arc seconds on the sky in normal operation. In front of each of two redundant detectors are filter wheels containing broad band filters. The filter wheels also contain Grisms for low resolution spectroscopy of brighter sources (lambda/Delta lambda 200) and a 4x field expander which will allow high spatial resolution images of the field center to be taken in optical light.

The pn-charge coupled device (pn-CCD) detector system was developed as the focal plane instrument of an x-ray telescope for the European photon imaging camera (EPIC) on the x-ray multi mirror (XMM) mission. The second cornerstone mission of the European Space Agency's Horizon 2000 plan performs high throughput imaging and spectroscopy of the x- ray sky in the domain of 0.1 keV - 15 keV. The pn-charge coupled device will also be used for a German x-ray astronomy satellite mission, called ABRIXAS (a broad-band imaging x-ray all-sky survey). While XMM will perform pointed observations. ABRIXAS will carry out an all sky survey with imaging telescopes. Both projects are planned to be launched in 1999. The homogeneous coherent sensitive area of the detector consists of a 6 cm by 6 cm large array of 12 pn-CCDs which are monolithically integrated on a single silicon wafer together with the first stage of amplification. The pn-CCD detector has been optimized for high-resolution x-ray spectroscopy and its performance is close to the theoretical limits given by the Fano noise. High quantum efficiency essential for the investigation of faint objects is accomplished over the whole energy range by a thin photon entrance window and a full sensitive detector thickness. A fast readout achieves excellent time resolution for the observation of pulsed x-ray sources and avoids pile- up for bright objects. The relevant performance parameters reflecting the state of the detector development are presented. The radiation hardness of the pn-CCD was verified for the ten year satellite mission. No significant increases in the thermally generated current, charge transfer losses and transfer noise occurred in the temperature range planned for detector operation. A correction of the signal charge losses, which occur already before irradiation in all types of charge coupled devices during the charge transfer to the anodes, is necessary to achieve the highest energy resolution of the detector. Methods to reduce the signal charge losses which were successfully tested, are described.

Superconductive tunnel junctions (STJs) are being developed as high energy resolution x-ray single photon detectors. Quasi-particle losses at the edges of such devices form a serious source of energy resolution degradation. A simple analytical relation for this source of resolution degradation has been derived from classical diffusion theory. Analyzing the x-ray spectra obtained for different series of STJs with various sizes, the edge reflectivity and the diffusion constant for our sputtered Nb films can be derived. This reflectivity can be explained by quasi- particle trapping. In addition progress is reported on the surface conditioning of single crystal, superconducting, Ta and Nb absorbers to be used for a highly efficient imaging x-ray spectrometer employing STJs as read-out.

ESA is undertaking an extensive program aimed at the fabrication of high quality superconducting tunnel junctions, based on Nb, to be used for the detection of radiation from infrared to gamma ray wavelengths. To extend our knowledge of current technology, devices have been manufactured using an alternative technology, consisting of epitaxial Nb bottom electrode film, and a variety of materials and layouts for the tunnel layers as well as the top film. A specific mask set has been designed to enable optimized fabrication, diagnostics and testing of these devices which also includes the first 3 by 3 Nb superconducting tunnel junction test array. Preliminary results are presented on the performance of various types of devices where the tunnel barrier characteristics and device size have been systematically varied.

Nb/Al/AlO_x/Al/Nb superconducting tunnel junctions (STJs) have been studied extensively as photon detectors, because of their intrinsic capabilities in terms of charge output and energy resolving power. A critical element in such an STJ is the aluminum layer which separates the superconductive Nb from the AlO_x tunnel barrier. In this paper, the role of this Al layer is investigated. The behavior of high quality STJs, differing by the Al thickness only, is analyzed. Five thicknesses ranging between 5 nm and 120 nm are considered. The charge output, the energy linearity and resolution for the case of 6 keV x-ray photons are discussed.

The Physikalisch-Technische Bundesanstalt (PTB) operates a radiometry laboratory at the synchrotron radiation facility BESSY. A beamline for detector calibration provides monochromatic radiation of tunable photon energy, high spectral purity (less than 1% false light contribution) and high radiant power in the photon energy range from 50 eV to 1500 eV. With that source of monochromatic radiation a cryogenic electrical substitution radiometry (ESR) is operated as a primary detector standard, which is capable of measuring radiant power in the order of some (mu) W with a relative uncertainty below 0.2%. The spectral responsivity of silicon photodiodes can be measured with a relative uncertainty of 0.3% by comparison to the ESR. On the other hand, silicon photodiodes have been introduced as easy-to- operate detector standards in the soft x-ray region in the PTB laboratory some years ago. The spectral responsivity of these photodiodes can be determined using a self-calibration technique, which is based on the knowledge of mean electron- hole pair creation energy, w, and the measurement of the angle of incidence dependence of the spectral responsivity. We deduced a constant value of w equals (3.64 plus or minus 0.03) eV for silicon in the soft x-ray region and improved the method to determine the charge collection efficiency of the photodiode. That allows us now to use silicon detectors as detectors of calculation spectral responsivity with a relative uncertainty of about 2%.

We propose MAXI (monitor of all-sky x-ray image), an x-ray all sky monitor on the exposed facility (EF) of the Japanese Experiment Module (JEM) on the International Space Station. The construction of the EF of JEM is scheduled in 2001. In the present design, MAXI consists of two slit scanning camera systems: one with one-dimensional position sensitive proportional counters, and the other with an x-ray CCD array employed for one-dimensional imaging with fast readout. We plan to monitor broad categories of x-ray sources, both galactic and extragalactic. In particular, we attempt to monitor dim sources (approximately several mCrab flux) on timescales of days to months.

The wide-field x-ray monitor (WXM) is one of the three scientific instruents onboard high energy transient experiment (HETE) satellite, which was launched in 1996. The primary objective of HETE is to carry out the first multi- wavelength study of gamma-ray bursts with UV, x-ray, and gamma-ray instruments mounted on a single, compact spacecraft. WXM has been designed to undertake comprehensive x-ray spectra observations and quickly determine small error boxes of GRB locations within a large field of view of about 1.5 steradian. It is based on the principle of coded aperture imaging. It has four identical one-dimensional position sensitive proportional counters (PSPCs), one pair in each of two orthogonal directions. Each PSPC is filled with 1.4 atm Xe (97%) and CO2 (3%), equipped with three resistive carbon anodes of 10 micrometer diameter, and sensitive to x-rays between 2 and 25 keV. It provides position resolution of about 1.0 mm (FWHM), and energy resolution of about 17% (FWHM) at 8 keV.

A development plan for an x-ray telescope based on polycapillary fiber optic technology is presented. The payload may be flown on either a sounding rocket for initial tests or on a balloon platform. For the latter, Fourier aperture synthesis imaging provides arcminute resolution over a fifteen arcminute field. The field-of-view is controllable to permit sensitive follow-up observations of localized sources. In this non-imaging mode, the telescope features high resolution spectrometry over an instrument bandpass from 3 to greater than or equal to 60 keV at a background level less than or equal to 5 milliCrab. Its continuum sensitivity for a 10⁵ second observation with 1 keV binning is better than or comparable to HEXTE below 60 keV.

In light of recent developments in hard x-ray focusing, work has been carried out at the University of Leicester, to investigate the use of high-Z materials (principally GaAs) for detecting x-rays in the 10 to 100 keV regime. The x-ray astronomy group at Leicester has been involved with developing the detectors and optics for several instruments including the Rosat wide field camera, JET-X an XMM, but both the grazing incidence optics, and the quantum efficiency of more conventional detectors, e.g. silicon CCDs, have limited the energy response to less than 10 keV. Ge, CdTe, HgI and GaAs all offer higher quantum efficiency than silicon and are being investigated as a possible means to extending the energy response of future telescopes, aimed at studying non-thermal processes beyond the iron lines. Detectors have been fabricated using bulk and epitaxially grown GaAs and tested at a range of temperatures between minus 130 degrees Celsius and room temperature. The behavior of bulk GaAs detectors is dominated by carrier trapping leading to imperfect charge collection efficiency (CCE) and traditionally poor spectral resolution. Noise-dominated spectra with 2 keV full width at half maximum (FWHM) are presented. The results of a Monte Carlo simulation of spectral performance are compared to the measured spectra. The modeling enables one to characterize the traps in terms of cross section density products and trap release times.

The precision gamma-ray spectrometer (PGS) on the Russian MARS-96 spacecraft is designed to measure 0.1-8 MeV gamma rays in order to determine the elemental composition of the Martian surface, to study solar flares, and to determine energy spectra and times of arrival of gamma-ray bursts. The PGS instrument contains two high-purity, n-type germanium crystals, each similar to the one used on the Mars observer mission. Each crystal is contained in a titanium can with helicoflex cryogenic metal seals. An annealing capability allows repair of radiation damage. The detectors are cooled via nitrogen heat pipes attached to a passive radiator mounted on the back side of a solar panel. The radiators are designed to keep the Ge detectors below 100 K during the interplanetary flight. The electronics include first-stage electronics mounted on each crystal can and 4096-channel pulse height analyzers. Two parallel channels of electronics are provided and can be cross-switched by telecommands. In November 1995 integration of the flight detectors with flight electronics and testing of the complete system cooled by the passive radiator were successfully completed. The energy resolution degrades to about 3 keV in the flight configuration. Warming the radiators indicated that for the worst case when the radiator views Mars at the equator the maximum temperature of the detectors will be limited by the diode action of the heat pipes to 118 K. Extensive calibrations with radioactive sources are in progress. We conclude that we have an improved design for planetary and gamma-ray burst studies and the PGS instrument is ready for launch in November 1996.

A new family of photodetectors based on hydrogenated amorphous silicon (a-Si:H) and silicon carbide (a-SiC:H) is described. They are p-i-n photodiodes whose thin layers are grown by glow discharge on cheap substrates as glass or flexible materials. Modulating the absorption profile in the semiconductor and the thickness of the layers, it is possible to select, during the growing process, the wavelength range where the photodetector is more sensitive. A first generation prototype of photodetectors optimized for UV detection was tested at room temperature and with no external bias voltage, illuminating it with visible and vacuum-UV radiation. The results show that the measured quantum efficiency is above 15% in the 58.4 - 250 nm spectral range and about 300 times lower at longer wavelengths (0.05% at 700 nm). An improved second generation has been also tested in the same experimental conditions and the preliminary data exhibit a better noise level (less than 1 pA), a higher response stability and an enhanced efficiency. A linear dependence on the radiation intensity has been verified over three orders of magnitude at 400 nm. Noise figure evaluation and response times will be also presented.

The light yield, or electroluminescence yield, of pure xenon for reduced electric fields below the ionization threshold (about 6 Vcm^-1torr^-1) was measured for pressures of 825, 570 and 276 torr using a uniform field gas proportional scintillation counter excited with 5.9 keV x rays. A linear behavior was exhibited from the 1 Vcm^-1torr^-1 electroluminescence threshold, but the measured yield (for lambda greater than 165 nm) diminished with the gas pressure. The best energy resolution obtained was 7.6% for collimated 5.9 keV x rays with xenon at 825 torr. A Fano factor of 0.26 was measured for the three xenon pressures.

We present investigations on the improvements in quantum detection efficiency (QDE) of microchannel plate (MCP) detectors resulting from the application of various photocathode materials. Nine different photocathode materials were deposited and their QDE measured in the soft x-ray and UV region from 12 angstrom to 1850 angstrom. Four of these materials (CsCl, RbCl, RbI, BaCl) significantly enhance the QDE performance of bare MCPs, and five materials were proven unsatisfactory (AgCl, LiCl, LiI, LiF, MgBr). CsCl has very high (greater than 90%) short wavelength QDE and both CsCl and RbI have UV QDE in the region of 40%. Our studies also include life testing of a KBr photocathode for a period of over 5 years. This shows good stability, and the angular response and photoemissive characteristics over time are described. The effects of long wavelength QDE activation of KBr by exposure to 2537 angstrom photons are discussed.

The high resolution camera (HRC) will be one of the 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. AXAF will perform high resolution spectrometry and imaging in the x-ray band of 0.1 to 10 keV. The HRC instrument consists of two detectors, the HRC-I for imaging and the HRC-S for spectroscopy. Each HRC detector consists of chevron pairs of microchannel plates (MCPs) and a crossed grid charge readout. Spatial resolutions of the HRC detectors are less than 25 micrometer (less than 0.5'). The HRC-I is a 100 by 100 mm detector primarily for imaging, the HRC-S is an approximately 30 by 300 mm detector which is optimized to function as the readout for the low energy transmission grating spectrometer (LETGS). The development of the HRC is a collaborative effort between the Smithsonian Astrophysical Observatory, University of Leicester UK and the Osservatorio Astronomico, G.S. Vaiana, Palermo Italy. In this paper we present the most recent design, development and testing of the HRC instrument.

In order to characterize the instrumentation on AXAF, each of the science instrument teams carries out sub-assembly calibrations. For the high energy transmission grating (HETG) group, this means individual measurements of the diffraction efficiencies of each of the 336 grating elements that goes into the completed HETG assembly. Measurements are made at a number of energies (corresponding to x-ray emission lines) which fix the parameters of a model. This model is determined from first principles and verified by extensively testing sample grating elements at synchrotron radiation facilities. Here we present new synchrotron radiation (SR) data obtained at the national Synchrotron Light Source (NSLS) and at the radiometry laboratory of the Physikalisch-Technische Bundesanstalt (PTB) using the electron storage ring BESSY in Berlin. The gratings are from AXAF flight lots, and we apply an improved data reduction technique which builds on our experience from last year (Markert et al., SPIE Proceedings 2518, 424, 1995). Our analysis takes into account the effects of small extended wings in the diffraction of the various orders in the NSLS data. Our goal is to obtain efficiencies in the 0th and plus/minus 1st diffraction orders which are accurate in the 1% level, except near absorption edges, where accuracies in the 5% to 10% level are required. With a few exceptions (discussed here) our new data/improved model meets these goals.

The detection efficiency of charge coupled devices (CCDs) in the x-ray band is dependent on the thickness of the active depletion layer in the silicon. This is typically under 35 micrometer and limited by the purity of available epitaxial substrates. For x-ray imaging, this results in a reduced CCD detection efficiency above 8 keV. In this paper, we show that by using a novel illumination geometry, CCDs can detect high energy (up to 100 keV) x rays with reasonable efficiency and good energy resolution. A novel 2-D imaging had x-ray detector based on this geometry is discussed.

The x-ray mirror calibration program for the JET-X telescope on spectrum-X has recently been carried out at the 130 m long Panter x-ray beam line of the Max Plank Institute fur Extraterrestriche Physik. The excellent spatial resolution achieved with these mirrors, 15 arcsec half energy width (HEW) at 1.5 keV and 19 arcseconds at 8 keV, has proved to be difficult to measure precisely using previously established calibration methods (involving either slit detectors or the ROSAT PSPC imaging proportional counter). New diagnostic techniques have, therefore, been developed using a CCD imaging camera which utilized newly available x- ray CCD technology. Details of the calibration technique and the performance of the camera are provided and results are compared with those obtained from the slit and PSPC detectors.

The principle of operation, the design, as well as parameters and characteristics of streak and frame image converters and cameras designed at the Research Institute of Pulse Technique for investigation of soft x rays are described.