The Advanced X-ray Astrophysics Facility (AXAF) presently undergoing definition studies is to be a major space-borne observatory in the United States Astronomy program. It will represent a major forward step in x-ray imaging capability. The x-ray imaging optics, a nested set of Wolter I telescopes will be larger, with response at higher energies, and of significantly improved angular resolution compared to all previous x-ray imaging telescopes. In order to establish that the technology, including manufacturing processes and metrology, are in place for the manufacture of the AXAF High Resolution Mirror Assembly (HRMA), a technology program was implemented. The final element of that program was the fabrication of a scaled Wolter I telescope to AXAF quality, and the subsequent testing of that telescope at the Marshall Space Flight Center X-ray Calibration Facility (XCF). This telescope is called the Technology Mirror Assembly (TMA). An overall description of the TMA program along with an overview of the test results and interpretation are presented here. Companion papers will describe the test procedures, results, and interpretations in much greater detail.

We describe the X-ray performance of the AXAF TMA in the 0.277 to 6.4 keV range. We verify the precise figure and smooth surface originally specified, and which were expected from the in-process optical and mechanical measurements. This paper primarily describes the test equipment and methods used, and gives examples of the detailed on-axis and off-axis data we acquired.

The AXAF Technology Mirror Assembly (TMA) was characterized prior to x-ray testing by properties measured mechanically or with visible light; these include alignment offsets, roundness and global axial slope errors, axial figure errors with characteristic lengths greater than about five mm, and surface roughness with scale lengths between about 0.005 and 0.5 mm. The x-ray data of Schwartz et al (1985) are compared with predictions based upon the mechanical and visible light measurements.

The Advanced X-ray Astrophysics Facility (AXAF), for which NASA and industry are currently conducting Definition and Preliminary Design studies, will provide a major advance in performance and observing opportunities beyond its predecessor space missions in X-ray astronomy, including Uhuru, Einstein and Rosat. The performance advances come from larger, higher quality mirrors with longer focal length that will extend the useful energy range and provide improved image resolution. Corresponding improvements will be made in observatory aspect determination and pointing stability. Increased observing opportunities come from facility-class operation of the observatory, including on-orbit maintenance and repair to provide potentially unlimited mission lifetime and on-orbit installation of new scientific instruments to take advantage of future advances in sensor technology. A summary of characteristics contrasting AXAF with the Einstein mission will be presented. Developing a design concept for AXAF that takes advantage of recent advances in technology and Shuttle-era capability for operations and servicing in space is a challenging process, requiring evaluation of a number of interesting, diverse design options for the X-ray telescope, science instrument accommodation and the host spacecraft. Major options for each of the areas will be identified and key considerations in selecting among them will be discussed. Specific elements addressed will include "beam switching" among the focal plane instruments, on-orbit access to the science instruments and components, major system interfaces, and observatory servicing.

Design alternatives for the AXAF observatory and intrument accommodation are discussed which will satisfy the x-ray astronomy missions and operations of the facility. The system engineering flow down and derivation of requirements from the science objectives are presented. The issues effecting the final subsystem selection are presented, along with a complete vehicle overview. Key subsystems include the structures, pointing control, science instrument integration, x-ray mirrors, aspect determination, and data handling.

The achievement of the derived goals for mirror surface quality on the Advanced X-ray Astrophyscis Facility (AXAF), Technology Mirror Assembly (TMA) required a combination of state-of-the-art metrology and polishing techniques. In this paper, we summarize the derived goals and cover the main facets of the various metrology instruments employed, as well as the philosophy and technique used in the polishing work. In addition, we show how progress was measured against the goals, using the detailed error budget for surface errors and a mathematical model for performance prediction. The metrology instruments represented a considerable advance on the state-of-the-art and fully satisfied the error budget goals for the various surface errors. They were capable of measuring the surface errors over a large range of spatial periods, from low-frequency figure errors to microroughness. The polishing was accomplished with a computer-controlled process, guided by the combined data from various metrology instruments. This process was also tailored to reduce the surface errors over the full range of spatial periods.

The top level goal for residual image degradation due to all mirror surface errors for the Advanced X-ray Astrophysical Facility (AXAF) Technology Mirror Assembly (TMA) was a Root Mean Square (RMS) image diameter of 0.38 arc second, approximately one order of magnitude tighter than for the highly successful HEAO-B, which represented the previous state of the art. In this paper, we cover the subdivision of the top level goal into a detailed error budget for various surface errors, and from there the subdivision into requirements on the surface metrology instrumentation. The derivation of the detailed error budget for surface errors required the definition of a new set of mathematical functions to describe surface errors on cylindrical optics, and a new type of analysis of the effect of mid-frequency surface errors on high quality X-ray images. The derivation of requirements on the surface metrology instrumentation pointed the way for the conceptualizing and design of several new metrology instruments which were beyond the previous state of the art.

A thin foil reflector X-ray telescope is proposed for ESA's high throughput spectroscopic X-ray mission, one of the cornerstone projects. Based on astrophysical requirements the performance specifications include large effective area at an X-ray energy of 8 keV and angular resolution better than 30 arcsec. To achieve this goal with 7 telescope units the radius of the outer mirror should be at least 30 cm, the focal length 8 m, and the mirror length 20 cm. The mirror thickness should be limited to 0.2 mm. Various mirror technologies such as dip-lacquered aluminium and electro formed nickel foils are examined. The surface roughness must also be controlled because scattering can ruin the focussing ability. A test assembly consisting of three representative mirrors has been used to investigate different supporting principles for the mirrors. The positions and surface shapes are measured mechanically and a ray-tracing program is used to translate the measurements into focussing properties.

A balloon borne hard X-ray experiment operating in the range 15-150 keV with a large sensitive area, high spectral resolution and fine imaging capability has been developed at IAS and AIT Institutes and succesfully flown the August 5th, 1985 from the stratospheric balloon. Base of Trapani-Milo (Sicily, Italy). During the flight that lasted. about 18 hours at an atmospheric depth of less than 3.5 g/cm² pointed observations were performed on the following sources: A05351-26, Crab, MCG 8-11-11 and MGC 4151. In addition several more sources were observed, in a scanning mode. In this paper we describe the instrumental configuration and present the pre-flight calibration as well as the in-flight performance.

Results of x-ray spectroscopy diagnostics of hot plasmas are presented as obtained in tokamak experiments and the enhanced information attainable with further instrumental development is discussed. The results obtained for tokamak plasmas of partially known and controllable conditions can be used to refine and test the x-ray diagnostic which should be used as reference in the analysis and interpretation of astrophysical data.

This paper describes a multiplex image coding system designed to be associated with a non-imaging spectrometer (Si(Li) or thermal spectrometer). The resulting instrument, an imaging spectrometer, could be used as a focal instrument for an astronomical grazing incidence telescope. The coding system consists in a movable mask with pseudo randomly distributed holes, located in the telescope focal plane. The pixel size lies in the range 100-200 microns. The close association of the coder with a Si(Li) spectrometer or with an X-ray bolometer gives an imaging spectrometer combining the good efficiency ( >50% between 0.1 and 10 keV) and energy resolution ( ΔE~100 eV for Si(Li),~ 10 eV (expected) for a bolometer) of these energy dispersive devices, with the spatial resolution of the mask.

The WATCH gamma-burst detector will be flown for the first time on the ESA microgravity satellite EURECA-1. EURECA is a retrievable satellite, launched and recovered by the Space Shuttle, the first launch is planned for March 1988 with a nominal 6 month mission time.

The scientific instrumentation on board of the Italian Satellite for X-ray Astronomy (SAX), foresees X-ray concentrators operating in the energy range 0.1 - 10 KeV with a spatial resolution of the order of 1 arcmin. This paper presents a study for the optics of such concentrators, based on several confocal nested mirrors. To reduce the loss of collecting area due to the thickness of the optics, it is necessary to use very thin mirrors. To achieve this result, still maintaining good optical quality, and to allow the construction of several concentrators at an acceptable cost, we propose the use of a replica technique by electroforming the mirrors from masters. The expected characteristics of the double cone geometry mirrors, together with preliminary results obtained with prototypes of electro-formed optics are presented.

Imaging X-ray mirrors has been developed in Czechoslovakia since 1970 by a way of two different replica technologies based on galvanoplastics and reactoplastics as a natural part of Czechoslovak X-ray astronomy program. Until' now about 30 mirrors with diameters between 1.7 and 24 cm were manufactured. Seven mirrors were flown in space experiments. The new technology used since 1981 allows to produce light-weight X-ray mirrors at relatively very low cost.The technology offers interesting possibilities in construction of (i) large arrays of identical optical systems, (ii) very small (microscopic) mirrors and (iii) lobster-eye type optics. Advantages and drawbacks of replica technology are discussed.

A triple axis X-ray spectrometer has been used to test the smoothness of mirrored surfaces. A perfect channel-cut Si or Ge crystal extracts Fe-ka radiation from a conventional X-ray tube. The radiation is incident on the test surface and the specularly reflected and scattered radiation from the surface is analyzed by another perfect channel-cut Si or Ge crystal. The channel-cut crystals provide an essentially "tailless" probe of the scattered radiation. The test surfaces in this study include three standard flats from the EXOSAT program, the AXAF-program and the ROSAT program, respectively, and test foils made in connection with the construction of a high throughput thin foil reflector telescope for the ESA X-ray Spectroscopy Mission XMM.

The first of eight x-ray telescopes is under construction for the LAMAR experiment. Each consists of two orthogonal sets of nested confocal one-dimensional parabolic plates. The reflectors are made from gold-coated float glass, selected for flatness from commercial stock. Each is initially bent to a cylinder by bonding a thin, highly curved titanium sheet to its inactive surface. The final parabolic figure is produced by an automated system that operates under the control of an IBM XT microcomputer. The system includes seven diode arrays that detect a visible light line image. Eight precise motorized linear translators operating under the control of the computer, tune the plate to the optimum figure. The plate is then fixed in position by epoxy bonds. The precision of the system is several seconds of arc, but the intrinsic flatness of the glass is expected to limit the half-power diameter (HPD) of the telescope to about 25 arcseconds. A prototype mirror made last year, with a less sophisticated system and with one-third the full number of plates not screened as stringently as our current stock, achieved a resolution of 35 arcseconds HPD. The new automated system will facilitate rapid, relatively low-cost production of mirror modules. It is applicable to the construction of larger mirror assemblies such as XMM with little increase in cost and complexity.

The vector and scalar theories of scattering as applied to X-ray scattering from mirror surfaces are reviewed. The results of both in the smooth surface limit are shown to be identical. In the smooth surface limit, the scalar theory has been extended to include the effects of finite surface conductivity leading to a quantitative description of the reduced specular reflection coefficient. Away from the smooth surface limit the scalar theory result has been calculated for a random roughness description of the scattering surface. Using this approach the intensity distribution has been evaluated independently of the statistics used to describe the distribution of surface heights.

The XUV Wide Field Camera is the second instrument on the German ROSAT Observatory. The instrument concept is described, the responses of the XUV mirrors, the microchannel plate detectors and the thin film filters are reviewed and the performance characteristics of the Wide Field Camera are summarised.

The calibration facilities and techniques for the Extreme Ultraviolet Explorer from 44Å to 2500Å are described. Key elements include newly designed radiation sources and a collimated monochromatic EUV beam. Sample results for the calibration of the EUVE filters, detectors, gratings, collimators and optics are summarized.

We present reflectivity and scattering measurements on samples of silicon carbide manufactured by a variety of processes. Measurements were made from near normal to grazing incidence at wavelengths in the range of 114 to 1216 Å. Our findings confirm that CVD silicon carbide displays the highest reflectivity at EUV wavelengths and normal incidence. We also demonstrate that at grazing incidence, silicon rich samples show reflectivity cutoff identical to polycrystalline silicon. From the limited data available for single crystal material, we conclude that CVD material has comparable performance.

Astronomy at photon energies above 10 keV is severely limited by the poor signal to noise ratios achievable with present instrumentation. This situation can only be significantly improved by the development of flux concentrating devices for hard X-rays. The feasibility of a concentrator for 511 keV X-rays based on Bragg reflections from high quality metal crystals has been studied theoretically and through laboratory measurements on sample crystals. Order-of-magnitude gains in sensitivity coupled with source localiza-tions at the 10-arcsecond level are predicted for such a Bragg-telescope. The price paid for relying on Bragg reflections is that the telescope sensitivity may have to be concentrated in a sequence of separated energy bands and that the field of view of the telescope is very limited - only a few square arcminutes.

Some recent methods are discussed which permit a two-dimensional imaging of the spatial distribution of X-rays and VUV photons with gaseous detectors; multiwire chambers, multistep chambers, chambers with parallel electrodes, and scintillation chambers.

We describe an application of the Penning Gas Imager or PGI' in X-ray astronomy. The PGI is an imaging proportional counter with improved energy and position resolution. A space version of the laboratory prototype detector has been designed and built at MSSL for use as a focal plane detector for the Soft X-ray Telescope (SXT). We present an application of the PGI to the imaging of diffraction patterns from biological specimens. Possible use of the PGI on XMM is also briefly discussed.

The addition of a preamplification region is shown to dramatically improve the performance of a standard multiwire proportional counter (MWPC). This improvement is a direct consequence of effecting a large degree of preamplification in a perfectly uniform electric field and then transferring a well defined portion of this charge to a MWPC running at a modest gain. In this way, very large overall gas gains can be achieved without compromising energy resolution. The resulting device is known as a multistep detector.

An investigation is made of the factors limiting the energy resolution of a gas scintillation proportional counter (GSPC). Several of these limitations originate in the drift region of such a counter and data is presented, giving a quantitative description of those effects. Data is also presented of a GSPC without a drift region, that therefore largely circumvents most of those degrading factors. The results obtained so far indicate that in that detector the limitation to the resolution is most probably due to cleanliness of the gas. Further research is underway in order to assess quantitatively the limiting factors in such a driftless GSPC.

Development of a detector for a Bragg spectrometer experiment is described, including the test setup and the read out electronics. A few examples of the position resolution are presented.We have built and put into operation a computer controlled test-stand with: A collimated x-ray beam in the energy range of 0.5 to 6 kev and the width of 50 to 200 microns, an x-y translation table for positioning the detector,a gas system for recirculating and filtering of different gas mixtures and pressures and an electronics system using the charge division method for event position determination. Charge pulses from the detector are digitized and analysed in a micro-processor where the position and energy spectra are stored. Background rejection is determined by energy, position and rise time windows in the micro-processor software.

A multiwire proportional counter as the prime focal instrument of the ROSAT X-ray telescope has been developed and built. It has a sensitive area of 80 mm diameter (corresponding to a FOV of 2 Deg.) and is designed for an X-ray energy range from 0.1 to 2.0 keV. The energy resolution for 0.93 keV is 45% (FWHM), averaged over the entire sensitive area. Local deviations of the gas gain from the mean value are as small as 3%. For X-ray energies at 0.28 and 0.93 keV, the mean position resolution is 0.4 and 0.25 mm (FWHM), respectively. Deviations of measured pinhole positions from their nominal positions are less than 0.02 mm (for 0.93 keV). Using different methods of background rejection, a rejection efficiency of better than 99% is achieved.

The development of a position sensitive proportional counter having a large drift volume is reported here. It incorporates a fluorescent gating technique which results in a large improvement in background rejection, over conventional proportional counters, and in addition offers the benefit of enhanced energy resolution (predicted to be ≈ 3% at 40 keV) above the K-shell of xenon.

We describe a new instrument for x-ray astronomy. The instrument, based on a high pressure (5 atm.), xenon filled, position sensitive Gas Scintillation Proportional counter (HPGSPC) is expected to feature an energy resolution better than 4% at 60 keV, an angular resolution of approximately 20 arc-minutes over the full energy range (4 to 100 keV) and a field of view (FOV) of up 30x30 degrees. A prototype flight unit of the gas cell on which the instrument is based is presently under technological development in the framework of the SAX project.

We describe the effect of X-ray absorption in the avalanche region of a parallel plate proportional counter. We calculate the magnitude of this effect for several different input spectra, using detectors having differing internal dimensions, gas compositions and pressures. The influence on the energy resolution of the EXOSAT and PGI parallel plate proportional counters is shown to be insignificant for most spectra.

NASA's Advanced X-Ray Astrophysics Facility (AXAF), currently scheduled for launch in the early 1990's, will be a powerful tool to aid in our understanding of the Universe. This paper gives an overview of the AXAF's capability and serves as an introduction to the detailed presentations which follow in these proceedings.

The proposed grating spectrometer for the Advanced X-Ray Astrophysics Facility (AXAF) covers the wavelength region between 2 and 140 Å. The wavelength resolution Δλ = 0.05 Å. The effective sensitive area as a function of wavelength is discussed. To illustrate the expected performance of the spectrometer some simulated spectra of a few interesting astrophysical objects are presented.

MIT's High Resolution X-ray Spectroscopy investigation on AXkF involves two complementary dispersive instruments, a Bragg Crystal Spectrometer (BCS) and a High Energy Transmission Grating Spectrometer (HETGS). The overall goal of the investigation is to study the physical condtions in celestial sources by means of detailed measurements of their X-ray spectra. High spectral resolution measurements can be used to perform diagnostics of emitting and absorbing matter, leading to knowledge of temperature, ionization state, elemental abundance, density and optical depth.

We describe a High Energy Transmission Grating Spectrometer that operates over the range 0.4-8 keV, gives resolving powers of 100-1000 and effective areas of 10-200 cm². The instrument, which is part of the MIT High Resolution X-ray Spectroscopy investigation, consists of a single array of grating facets of two types: medium energy gratings of 0.6 μm period, 0.5 μm thick silver mounted behind the outer three AXAF mirrors, and high energy gratings of 0.2 μm period, 1.0 μm thick gold mounted behind the inner three mirrors. The gratings are oriented so as to correct for coma and so that the medium and high energy spectra form a shallow "X" at the AXAF focal plane. The thicknesses and materials of the gratings are selected to give total first order diffraction efficiencies of up to 50%. The gratings are fabricated on thin polyimide films using techniques of X-ray lithography. They have been tested at energies of 5 to 15 keV. The minimum detectable line strength for point sources observed with the HETGS and a CCD detector is 1-10 x 10^-6 photons cm^-2 s^-1. Likely targets include normal stars, binary X-ray sources, active galactic nuclei and quasars. The HETGS can also be used to give moderate resolution spectra of slightly extended sources and monochromatic images of sources with strong lines, such as supernova remnants in nearby galaxies.

The AXAF CCD Imaging Spectrometer (ACTS) is currently being defined as a possible focal plane instrument to be flown on the Advanced X-ray Astrophysics Facility (AXAF). The imaging spectrometer consists of an array of charge coupled devices (CCD's) to be placed at the focus of the AXAF mirrors. The array will provide high angular resolution (~ 0.5 arc seconds), moderate spectral resolution (~ 150 eV) over the energy range 0.1 to 10 keV, temporal resolution down to ti 60 p sec, and single photon quantum detection efficiencies of up to 90%. X-ray sensitivity for a point source exceeds 10^-15 ergs/cm² sec fort a 10⁵ sec exposure. When used in conjunction with the objective gratings, the array will yield wavelength resolution of up to λ/Δλ of about 200.

We describe a novel device which combines the high quantum efficiency of a photoelectric detector with the high energy resolution of a dispersive spectrometer in a system that operates simultaneously over the whole AXAF bandpass. It is basically an X-ray calorimeter, in which the temperature rise of an X-ray absorber following the deposition of energy from a single X-ray photon can be measured to an accuracy expected to be of order one part in 1000 at 6 keV.

The HRC (High Resolution Camera) is a photon counting instrument to be flown on the Advanced X-Ray Astrophysics Facility (AXAF). It is a large field of view, high angular resolution, detector for the x-ray telescope. The HRC consists of a CsI coated microchannel plate (MCP) acting as a soft x-ray photocathode, followed by a second MCP for high electronic gain. The MCPs are readout by a crossed grid of resistively coupled wires to provide high spatial resolution along with timing and pulse height data. The instrument will be used in two modes, as a direct imaging detector with a limiting sensitivity of 10^-15 ergs/cm² sec in a 10⁵ second exposure, and as a readout for an objective transmission grating providing spectral resolution of several hundreds to thousands.

We review the design of the spectrometers included on the Extreme Ultraviolet Explorer (EUVE) astronomical satellite. The spectrometer design is novel, consisting of three variable line space reflecting gratings mounted in a slitless configuration behind a grazing incidence telescope. A collimator is employed to reduce diffuse background radiation to negligible lev-els. Prototype gratings have been mechanically ruled and the best samples recover over 80% of the theoretical efficiency of perfectly formed grooves, reaching 30% absolute at 114Å. Groove profile measurements made using a Talystep profilometer and electron micrographs are compared, and found to agree with the blaze angles derived from reflectivity measure-ments. In the final design, grating blaze angles have been optimized to minimize second order contamination. Prototype collimator EUV measurements show peak transmission of 90% of theoretical, with transmission outside the main lobe of less than 0.5%, and a scattering level less than 10^-4arcmin^-1. Using measured performance characteristics of the collimator, telescope, gratings and detector, we have determined the sensitivity of the instrument for a 40,000 sec observation; the average 3-σ sensitivity of continuum flux is approximately 2x10^-27erg/cm²/sec/Hz. This is a factor of 100 dimmer than a bright known EUV source, and is comparable to the sensitivity of the all-sky survey which will be carried out on the EUVE.

We present a spectrometer design candidate for the X-ray Multi-Mirror (XMM) observatory, being planned by the European Space Agency (ESA) as a long-lived large-area array of telescopes. The science requirement of moderate resolution (E/ΔE ~ 100) spectroscopy in a two octave region (0.5-2 KeV) with extremely high throughput (effective area > 500 cm²) results in the use of grazing incidence reflection gratings. Due to the low image quality of the telescopes (~ 1 minute of arc), the grating dispersion must be maximized by use of the classical grating mount in which the spectrum is dispersed within the plane of incident radiation. Due to the small field of view afforded by the x-ray telescopes, the gratings must be situated in the converging beam at the exit of the telescope. A spectrometer module consists of a thin-foil conical mirror telescope, a stack of plane varied-space reflection gratings and an imaging proportional counter. This system is analyzed on the basis of dispersion, geometric aberrations and efficiency. At a spectral resolution of 0.15 Å, a twenty module XMM would attain an average effective area of ix, 900 cm², reaching twice this value at the peak wavelength (15 Å). Similar throughput is obtained in second order centered at 7.5 Å, the two spectral orders separated by the non-dispersive energy resolution of the proportional counter. Continuous spectra are obtained in the 6-25 Å band (0.5-2 KeV), and can be extended to 45 Å if desired by tuning of the grating. The instrument sensitivity is sufficient to allow the first spectral detection of soft x-ray features in external galaxies, with access to an estimated population of several hundred active galactic nuclei. Such observations will expand vastly the roles feasible for spectroscopy in x-ray astrophysics, marking the beginning of a new era in space astronomy.

There exists a need for a high resolution (E/ΔE >500-1000), imaging (~5x5 arcmin pixel) spectrometer which is capable of studying sources with appreciable angular extent (up to 1-2 deg) and which emits line spectra from a broad range of highly ionized plasmas (oxygen through iron). A large flat objective crystal couples nicely to a modest resolution but high throughput x-ray concentrating telescope to produce high dispersion images of diffuse x-ray sources in each of the several lines present in the spectrum. Unprecedented spectral resolution is provided for point sources and, provided that they do not vary on rapid time scales, a spectrum can be scanned over a wide energy range with unparalled sensitivity.

An X-ray spectrometer which is sensitive in the 0.5-7 keV energy range has been studied. The rays which are Bragg reflected from a doubly bent crystal positioned downstream of the focal plane of a grazing-incidence concentrator are focused along the axis of a position sensitive detector. High throughput, simultaneous (scanning free) photon recording throughout the spectral range of interest, and crystal limited resolution which is achieved with a concentrator using a conical approximation to Wolter-1 optics are the main advantages. The sensitivity for spectral line detection in the presence of background may compete with that of broadband detectors.

A versatile X-ray spectrometer/scatterometer for the study of X-ray optical elements such as grazing incidence mirrors, crystals and X-ray gratings has been built and put into operation at the Danish Space Research Institute. The spectrometer is built on a 1.5 m long granite bench with the X-ray source located at one end of the bench where it can be rotated around a fixed vertical axis. The beam defining elements are perfect crystals of Si, Ge or Quartz. With these it is possible to define a highly collimated beam of a few arcsec FWHM in the scattering plane. Examples of measurements on various X-ray optical elements are presented. In particular, a study of intrinsic and mosaic diffraction from test crystals is presented in detail. The deconvolution of the experimental data is discussed in general terms and as an example the results of a calculation of the spectrometer resolution function for the four crystal set-up employed in the above mentioned crystal study are presented.

Detector systems based on the high-gain microchannel plate (MCP) electron multiplier have been used extensively for imaging at soft x-ray wavelengths both on the ground and in space. The latest pulse-counting electronic readout systems provide zero readout-noise, spatial resolutions (FWHM) of 25 microns or better and can determine the arrival times of detected photons to an accuracy of the order of 100 ns. These systems can be developed to produce detectors with active areas of 100 mm in diameter or greater. The use of CsI photocathodes produces very high detective quantum efficiencies at wavelengths between about 100 and 1Å (~0.1 to 10 keV) with moderate energy resolution. The operating characteristics of the different types of soft x-ray MCP detector systems are described and the prospects for future developments are discussed.

We present new results in four areas of microchannel plate (MCP) X-ray detector operation. The performance in pulse counting mode of MCPs with 8 micron channel diameters is reported. The effects on MCP quantum detection efficiency and energy discrimination of multiple CsI coatings are described. A new mode of operation of two-stage multipliers is evaluated. Replacing the conventional electron-accelerating inter-plate potential difference by a retarding field is shown to result in definite advantages with regard to X-ray energy discrimination and detector lifetime. The source of the MCP internal background is discussed.

We describe the development of microchannel plate detectors for the Wide Field Camera (WFC) XUV (50-300Å) sky survey experiment on ROSAT. A novel feature of the detector design is that the microchannel plates (MCPs) and their resistive anode readout are curved to the same radius as the WFC telescope focal surface. We show that curving the channel plates is not detrimental to gain uniformity. We describe the design of a curved resistive anode readout element and contrast our measurements of spatial resolution, global and local uniformity and temperature coefficient of resistance with the poor performance recently ascribed to resistive anodes in the literature. We present the first measurements of the quantum detection efficiency of a CsI-coated MCP in the wavelength range 67-256Å.

A theoretical model is presented which predicts the output response of a CCD to soft X-ray spectra. The model simulates the four fundamental parameters that ultimately limit CCD performance: Quantum efficiency, charge collection efficiency, charge transfer efficiency, and read noise. Simulated results are presented for a wide variety of CCD structures, and general conclusions are presented about achieving a practical balance of sensitivity, energy, and spatial resolution for an AXAF instrument. We compare the results of the analysis to an existing state-of-the-art CCD and project improvements which will be made in the near future.

The X-ray performance of two new types of GEC P8600 CCDs have been measured. One, a conventional thin depletion layer device, possesses very low noise characteristics enabling good X-ray energy resolution to be achieved, but with only modest quantum efficiency (10% at 5.9 keV). The other, a deep depletion device fabricated on high resistivity silicon also possesses the desired low noise performance (8 electrons rms), combined with much improved quantum efficiencies (60% at 5.9 keV). Degradation of energy resolution due to charge spreading effects has also been overcome through use of the deep depletion layer and the new device has a capability for rejection of background charged particles of around 96%. The development is for spectroscopic instrumentation for X-ray astronomy.

The detection of single events like the absorption of γ or X-rays and a or p particles with cooled thermal detectors is now well established and first resolutions obtained are promising. We have more thoroughly investigated the possibilities of the composite bolometer which offers the advantage of separating the absorbtion, thermal diffusion and thermometric functions. An optimal configuration is the diamond composite bolometer with a monolithic thermistor. Experimental results are presented on the simultaneous detection of different kinds of events (α's + γ -rays and β's + X-rays) at 1 K temperature. These results confirm the high linearity of this detector (better than 1.5 per cent from 20 KeV to 6 MeV) and its ability to accept rather high counting rates (> 100 per second). As a conclusion, we present an example of application to X-ray astronomy and we underline some problems or developments to be studied for a space mission.

A prototype optical image intensifier is coupled to a phosphor-coated fibre optic to provide an imaging soft X-ray detector. We show that high quantum efficiency is combined with high position resolution and some energy resolution. We estimate the dark current and particle background rejection factors of this detector and discuss its suitability for space applications such as X-ray astronomy.

In this paper we describe new types of VUV monochromators using only plane type V holographic gratings. New design rules using physical optics associated with the phase balancing method are suggested to achieve super resolution.