The AXAF, the x-ray component of NASA's great observatories, will launch in 1999. As integration and testing of the flight system are concluding, analysis of the ground calibration data continues. This analysis verified AXAF's unique capabilities for high-resolution imaging and for high-resolution dispersive spectroscopy. However, it finds unexpectedly high residuals between the data and the model for effective area of the AXAF optics. Reconciling the physical model with the data, to an accuracy of a few percent, remains a goal of the analysis and interpretation of the calibration data.

The Smithsonian Astrophysical Observatory uses the HRMA X- ray Detection System (HXDS) to calibrate the High-Resolution Mirror Assembly of the Advanced X-ray Astrophysics Facility AXAF. Apart from two high-purity-germanium solid-state detectors (SSDs) with good energy resolution and very high efficiency at higher energies, the detection system comprises seven flow proportional counters (FPCs) and one microchannel-plate High-Speed Imager. For the lower energy range, the FPCs are more appropriate. They have been calibrated at the radiometry laboratory of the Physikalisch- Technische Bundesandstalt, using the electron storage ring BESSY. For the determination of the absolute quantum efficiency two methods have been applied. First, the detector response was measured in the lower energy range 0.1 keV to 1.7 keV at several discrete energies using monochromatized radiation. The absolute photon flux has been determined by Si n-on-p photodiodes, calibrated against a cryogenic electrical-substitution radiometer used as primary detector source standard BESSY, which can be calculated very accurately. Combining both measurements the determination of the detection efficiency over the entire desired spectral range was possible with a typical relative uncertainty around 1 percent to 2 percent in the central energy range.

The coincidence of multiple x-rays in a detection cell within one CCD frame - an effect known as pile-up - is a significant source of spectral contamination for bright sources observed with the AXAF CCD Imaging Spectrometer (ACIS). Investigation of algorithms for correcting contaminated spectra is underway. In case where such algorithms fail, the observer may wish to discard events for the core of the AXAF point spread function (PSF), computing spectra using only events from the PSF wings, where pile-up effects are reduced. This work investigates the effectiveness of this technique for an isolated on-axis point source, using event lists produced by a Monte Carlo simulation of the ACIS instrument.

The HETGS on AXAF is the coordinated operation of the AXAF High-Resolution Mirror Assembly (HRMA), the high-energy transmission grating (HETG), and the grating-readout array of the AXAF CCD Imaging Spectrometer (ACIS-S). XRCF calibration data are analyzed to verify the Rowland geometry design of the HETGS. In particular, ACIS-S imaging of quadrant shutter focus test is used to probe the focus, alignment, and astigmatism of the spectra produced by diffraction through the high and medium energy gratings of the HETG. The experimental results are compared to expected values and to results obtained with the AXAF simulator, MARX.

In Phase 1 of AXAF testing at the X-Ray Calibration Facility (XRCF), calibrated flow proportional counters (FPCs) and solid-state detectors were used both in the focal plane and as beam-normalization detectors. This use of similar detectors in the beam and focal plane combined with detailed fitting of their pulse-height spectra allowed accurate measurements of the HRMA absolute effective area with minimum influence of source and detector effects. This paper describes the application of these detectors and fitting techniques to the analysis of effective area and efficiency measurements of the AXAF transmission gratings, the High Energy Transmission Grating (HETG) and the Low Energy Transmission Grating. Because of the high dispersion of these gratings the analysis must be refined. Key additional ingredients are the inclusion of detailed x-ray source models of the K and L lines based on companion High-Speed Imager microchannel-plate data and corrections to the data based on high-fidelity ray-trace simulations. The XRCF- measured efficiency values that result from these analyses have systematic errors estimated in the 10-20 percent range. Within these errors the measurements agree with the pre-XRCF laboratory-based efficiency models of the AXAF grating diffraction efficiencies.

In order to probe for small scale spectral features of the High Energy Transmission Grating Spectrometer (HETGS) and the low energy transmission grating, we performed test at the AXAF X-Ray Calibration Facility (XRCF) using a very bright continuum source. THE Electron Impact Point Source (EIPS) was used with the Cu anode and operated at high voltage and low current in order to provide a bright continuum at high energies. The AXAF CCD Imaging Spectrometer Spectroscopy detector (ACIS-S) was used to discriminate orders and to provide high throughput when operate in continuous clocking mode. Many spectral features are observed but most of them are emission lines attributable to the source spectrum. We find that the current models for the HETG efficiency, the LETG efficiency and the AXAF High Resolution Mirror Assembly effective area predict very well the observed fine structure near the Au and Ir M edges where the models are most complex. Edges in the detector filter and quantum efficiency (QE) curves are somewhat more sharply defined in the data than in the current modes. By comparing the positive and negative dispersion regions, we find no significant efficiency asymmetry attributable to the gratings and we can further infer that the QEs of the ACIS-S frontside illuminated (FI) chips are consistent to +/- 10 percent. On the other hand, we derive the ratio of the QE for the backside illuminated (BI) chips relative to that of the FI chips and show that it deviates for the expected ratio. This deviation may result from grade differences due to operation in CC mode while most calibration data are obtained in timed event mode.

Tests of the High-Energy Transmission Grating Spectrometer (HETGS) for the Advanced X-Ray Astrophysics Facility (AXAF) showed anomalous scattering of monochromatic radiation. The grating resolving power (E/dE) is of the order 1000, but test designed to search for small-angle scattering by the gratings showed events with significant deviations from the dispersed grating orders and concentrated along the dispersion direction. In this paper, we present a general overview of grating scatter as a result of fluctuations in the grating bar geometry. The grating scatter observed at the AXAF-X-Ray Calibration Facility is shown to be consistent with what one expects from scatter due to deviations in the grating bar geometry form perfect bars. For the purposes of modeling, a rectangular bar mode is adopted and bar parameters are deduced via fitting the model to the scattering data. The correlations deduce from this model lead to a simple physical picture of grating bar fluctuations where a small fraction of the bars, e.g., 1 in 200 are leaning.

The Advanced X-Ray Astrophysics Facility High Resolution Camera was calibrated at NASA's X-Ray Calibration Facility during March and April 1997. We have undertaken an analysis of the effective area of the combined High Resolution Mirror Assembly/High Resolution Camera using all data presently available from these tests. In this contribution we discuss our spectral fitting of the beam-normalization detectors, our method of removing higher order contamination lines present in the spectra, and the corrections for beam non- uniformities. Using an approach based upon the mass absorption cross-section of Cesium Iodide, we determine the quantum efficiency in the microchannel plates. We model the secondary electron absorption depth as a function of energy, which we expect to be relatively smooth. This is then combined with the most recent model of the telescope to determine the ensemble effective area for the HRC. The ensemble effective area is a product of the telescope effective are, the transmission of the UV-Ion shield, and the quantum efficiency of the microchannel plates. We focus our attention on the microchannel plate quantum efficiency, using previous result for the UV-Ion shield transmission and telescope effective area. We also address future goals and concerns.

Measurements at XRCF produced calibration data of the high orders of the AXAF High Energy Transmission Gratings at several energies. These tests provide a necessary complement to the limited set of laboratory high-order measurements on each of the flight gratings. We present the analysis and results of these measurements made at XRCF in Phase 2, where the flight detectors, HRC and ACIS, were employed.

AXAF telescope witness mirror calibrations have been carried out on ALS Beamline 6.3.2 in July 1997 and Jan-Feb 1998 to ascertain whether sufficient beam purity and signal to noise were available over the energy range 50-1000 eV. An overall accuracy of 1 percent is necessary on reflectivities to meet AXAF program requirements. Some beamline variations were incorporated - based on two previous test runs. Various filter/order-sorter combinations were used to control beam purity. A test involving strength of the N-edge dips in reflectivity versus sample angle to the beam showed the NVII, NVI, NIII, NII, and NI edges in roughly expected proportions. This verified adequate purity in all filter/order-sorter channels except the 260-454 eV channel that includes the NV and NIV edges just above the carbon K- edge. We discuss a future solution of this puzzle by other test for evaluation of the carbon contamination layer. Oxygen contamination is also ubiquitous on Ir mirrors and foils. These problems can also be handled through optimization of the data acquisition and use of control samples. In reflection Ir NIII appears out of the noise as two doublet-like bumps. Ir NII has so far been observed near the noise level < 2 percent. Averaged over many scans it too appears to be doublet-like. Scans through the NI edge near the noise level are compatible with a doublet-like or broad feature from 685-707 eV. transmission data give the NI and NIII edges better. Ir NIV and NV edges are not yet measurable for systematic reasons. NVI and NVII appear to be normal edges. Angle scans to derive the Ir and Cr layer thicknesses are feasible at approximately 900-920 eV. Reflectivities can be reliably measured at small angles to 1300 eV. This will be useful for overlap with measurements at NSLS. Optical constants derived from reflectivities in most segments of this energy range will meet requirements for AXAF. Transmission measurements are being pursued in addition, for confirmation and to augment some segments.

As calibrations of AXAF mirrors in the 2-12 keV range are near completion, we can report that the archive is complete for the scheduled number of mirrors over the 5-12 keV range, and also over the 2010-6200 eV range. Analysis of the results for optical constants and coating layer parameters is now proceeding rapidly. To date, we have derived optical constants from 39 mirrors over 5-12 keV using our existing Fresnel Equation model, with uniform layers of Ir, Cr, and Zerodur, and the roughness algorithm of Nevot and Croce. The analysis method has been presented in our earlier papers, but its application has been expanded to all three varieties of witness mirrors use in AXAF's qualification and production coating runs. For the first and most consistent variety, which have 1 angstrom roughness, reflectances are indistinguishable from mirror to mirror save for thickness variations between coating runs. Residuals of the fits for optical constants become large when reflectance values below 18 percent are included in the fits. If such data points are ignored, values of (delta) (E) and (beta) (E) very much like those of Henke et al. over 5-11 keV are obtained. Residuals are at the 0.6-0.8 percent level, which meets calibration requirements but exceeds experimental noise. For the second variety of witness mirror, polished to obtain roughness specification similar to the flight mirrors, fits approximately within the noise level of the measurements may be obtained over 5-11 keV, for reflectance values down to 5 percent. The (delta) (E) is essentially the same as that obtained from the 1 angstrom flats; however (beta) (E) is higher by approximately 3-4 percent systematically, and the mirror-to-mirror variation is larger. The third variety of mirror was obtained with 5-7 angstrom nominal roughness. Residuals to the fits are large for the entire range of angles, in some case exceeding 2 percent with a sinusoidal character through the critical angle. Coating layer depths are similar to those found for the other mirror types, with good precision. We discuss results along with possible improvements to the model and experiments to verify it.

XRCF measurements of the flight AXAF High Energy Transmission Grating Spectrometer throughput were used to determine absolute effective areas. The result are compared with component models of the HRMA, HETG and the ACIS-S. The comparison provides an independent view on HETG efficiencies as well as the detector efficiencies along the dispersion direction. Using the XRCF double crystal monochromator measurements in the range from 0.9 to 8.7 keV, the effective areas in the 1st order MEG were determined with an accuracy of better than 10 percent, in the 1st order HEG better than 15 percent throughout most of the energy range. This is within the goal set for the XRCF measurements to refine state of the art composite component model predictions, which in the future will allow us to draw conclusions on the in-flight HETGS absolute effective area.

The Advanced X-ray Astrophysics Facility (AXAF) ground calibration program, easily the most extensive in the history of high energy astrophysics, requires careful attention to the verification of its validity for on-orbit operations of the observatory. The purpose of the Flight Contamination Monitor (FCM) is to verify the transfer of the AXAF absolute flux scale calibration from ground to on-orbit operations and to measure or bound any changes in molecular contamination on the AXAF mirrors. This paper reports the current status of the analysis of FCM measurements taken during ground calibration. The FCM measurements during the AXAF activation phase will be the first look at the on-orbit AXAF performance.

Two monochromator sources were used during the AXAF calibration at Marshall Space Flight Center's X-ray Calibration Facility. Data acquired using these sources require special analysis owing to large spatial variations in the monochromators' beams and to higher-order contributions to the spectral content. A description of the two monochromators is given, followed by a discussion of the spectral and spatial content as monitored by beam- normalization detector flow proportional counters. Emphasis is given to the methodology employed in determining the spatial content through fits to beam uniformity measurements. A model is described which adequately represents the beam spatial properties over the range of source conditions encountered during calibration.

We describe the analysis of effective area measurements for the AXAF High Resolution Mirror Assembly (HRMA) and the AXAF CCD Imaging Spectrometer (ACIS). The measurements were obtained at the X-ray Calibration Facility (XRCF) in Huntsville, AL, during April 1997. Measurements obtained with two frontside-illuminated (FI) charge-coupled devices (CCDs) in the imaging array and the backside-illuminated (BI) CCD located on-axis in the spectroscopic array are considered. We compare the XRCF effective area measurements to independent, semi-empirical model predictions constructed using the product of the efficiencies of the AXAF components. The XRCF measurements, in general, confirm the reliability of the model at most energies, but only after correcting the data for several effects related to event pileup. However, after applying the corrections, the uncertainties in the XRCF measurements remain uncomfortably large. We suggest several future avenues of investigation that should improve our knowledge of the HRMA + ACIS effective area.

Acquisition of ground calibration data from the AXAF CCD Imaging Spectrometer, one of two focal plane instruments on NASA's Advanced X-ray Astrophysics Facility, was completed in 1997. Here we summarize results of the detector level calibration effort. Our calibration program has included measurements of CCD response to undispersed synchrotron radiation, measurements of x-ray absorption fine structure, and of sub-pixel structure in the detector. Errors in the energy scale are at the level of a few tenths of one percent, and detection efficiency errors are no large than a few percent. We have also obtained new insights into the mechanisms by which the CCD gate structure and channel stops influence the CCD spectral redistribution function.

The flight AXAF CCD Imaging Spectrometer (ACIS) and the High-Resolution Mirror Assembly (HRMA) telescope were extensively calibrated at NASA MSFC's X-Ray Calibration Facility (XRCF). We present result based on HRMA/ACIS characteristics that were obtained with the following tests: (a) Point-Spread Function (PSF) tests measuring the core and wings of the PSF on-axis and at several off-axis positions, at the point of ideal focus. (b) Effective-Area (EA) test measuring the total effective collecting area over the PSF at many energies. We investigate the dependence of the effective area and energy response of ACIS/HRMA as a function of several ACIS parameters. (c) Count-rate- linearity (pile-up) test measuring the effect of increasing the mean incident rat of photons per pixel on the PSF, and EA, source centroid, and photon detection. The goal of the calibration is to provide accurate estimates of the in-orbit performance of the ACIS/HRMA instrument and to enable translation of in-orbit measurements to absolute values of the incident x-ray flux and physical models of the source emission.

The AXAF X-ray mirrors underwent thorough calibration using the X-ray Calibration Facility (XRCF) at the Marshall Space Flight Center in Huntsville, AL from late 1996 to early 1997. The x-ray calibration made novel use of the x-ray continuum from a conventional electron-impact source. Taking advantage of the good spectral resolution of solid-state detectors, continuum measurements proved advantageous in calibration the effective area of AXAF's High-Resolution Mirror Assembly (HRMA) for the entire AXAF energy band. The measurements were made by comparing the spectrum detected by a SSD at the focal plane with the spectrum detected by a beam normalization SSD. The HRMA effective area was calibrated by comparing the measurements with the HRMA raytrace model. The HRMA on-orbit performance predictions are made using the calibration results.

The ACIS flight instrument was recently extensively calibrated at the X-ray Calibration Facility at MSFC. For the analysis of a subset of the ACIS calibration data we have employed an automated even filtering software package developed at PSU. We present result describing the dependence of the Effective Area and Energy Response of ACIS/HRMA as a function of grade selection, split event threshold, CCD and CCD amplifier, and off-axis angle. The main goal of this study is to facilitate the selection of the appropriate ACIS parameters that optimize a desired feature in an observed ACIS spectrum and may also guide observers in selecting the appropriate CCD for the observation. Optimizing a particular feature in an ACIS observation in general may require making a trade-off between effect area and energy response of AXAF/ACIS. The present analysis will facilitate the selection of the appropriate grades, CCD, CCD amplifier and spilt even thresholds needed to attain the optimal point.As an illustration of the effectiveness of this approach we present several case studies of typical astrophysical source spectra in which we enhance a particular scientific feature in the observed ACIS spectrum by the appropriate selection of ACIS parameters.

The high throughput x-ray spectroscopy mission (XMM) is a 'Cornerstone' Project in the ESA long-term Program for Space Science. The satellite observatory uses three grazing incidence mirror modules coupled to reflection grating spectrometers and x-ray CCD cameras. Each XMM mirror module consists of 58 Wolter I mirrors which are nested in a coaxial and confocal configuration. The calibration of the mirror system includes the development of a representative numerical model and its validation against extensive calibration test performed on ground at the CSL and PANTER test facilities. The present paper describes the calibration of the x-ray image quality of the first XMM flight mirror module.

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. Each XMM mirror module consists of 58 Wolter I mirrors which are nested in a coaxial and cofocal configuration. The calibration of the mirror system includes the development of a representative numerical model and its validation against extensive calibration tests performed on ground at the CSL and PANTER test facilities. The present paper describes the calibration of the x-ray effective area of the first XMM flight mirror module.

Keywords: XMM, X-ray astronomy, Wolter I telescope, grazing incidence optics

The X-ray Multi-Mirror Mission is one of the four 'Cornerstone' projects in the ESA Long-Term Program for Space Science. Presently, five XMM Mirror Modules (MM) have been tested in the FOCALX facility of CSL. The MMs are illuminated by a vertical EUV collimated beam allowing to get the optical performance in an effective flight configuration. To fully analyze the MM characteristics, reflectivity measurements are performed in X-ray thanks to a pencil beam. The reflectivity measurements of single shell are performed at Al, Au, Cu, Mo lines between 1.5 and 13 keV. This information is used to evaluate the effective area in X-rays. Wing scattering measurements are performed and show a good correlation with the Power Spectral Density measured with a PROMAP microscope interferometer during mirror shell manufacturing. This paper deals first with the presentation and comparison of the result achieved on the five MMs. In a second step the results of complementary tested, performed to cross check the data and to get a better understanding of the MM behavior, are discussed.

The high throughput x-ray spectroscopy mission XMM is a 'Cornerstone' Project in the ESA long term program for Space Science. This observatory, due to be launched in 1999, has at its heart three heavily nested Wolter 1 grazing incidence x-ray telescopes which will provide a large collecting area. This optical system has a spatial resolution of 16 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. Beginning of this year, all the four Flight Model telescopes have been delivered, after two years of intense production of the x- ray mirrors and after a challenging machining of the x-ray baffle. The measurements carried out at the Center Spatial de Liege and at the Max Planck Institute indicate x-ray performance significantly better than the specifications. This paper first provides a concise description of the design of the telescope with the emphasis on the x-ray mirrors and the x-ray baffles. We then analyze and compare the x-ray and optical test results achieved on the four Flight Models of the XMM telescope. In particular, we address two important issues: the determination of the focal length of the telescopes and the improvement of the scientific mission by the implementation of an x-ray baffle. Finally, based on the lessons learned from XMM experience, the prospective on the next generation of ultra thin x-ray mirrors is also presented.

The Reflection Grating Spectrometer (RGS) aboard XMM is a large collecting area, dispersive soft x-ray spectrometer providing high resolution and a bandpass of 5-35 angstrom. We have built and characterized the two, nearly identical, flight model reflection grating arrays for the RGS instrument. Precision alignment and assembly of 182 grating elements into each array was performed at Columbia Astrophysics/Nevis Laboratory, and end-to-end X-ray calibration and testing were performed at the MPE-Panter facility. Preliminary results from the calibration are summarized, and reconciliation of those results with baseline optical design, simulations and error budgets are discussed.

ABRIXAS is a German satellite project - to be launched in spring 1999 - which will perform the first imaging x-ray all-sky survey in the 0.5-10 keV band thus being a complement to the ROSAT all-sky which covered the 0.1-2.4 keV range. The motivation of the project is a complete survey of sources that are missed by the ROSAT survey due to absorption. ABRIXAS will be also an ideal pathfinder for the forthcoming missions XMM and AXAF which will be launched in 1999, too. The ABRIXAS observatory will contain seven identical mirror modules, each consisting of 27 nested gold coated nickel shells of Wolter type I with a maximum diameter of 16 cm and a focal length of 160 cm. The optical systems are constructed by Carl Zeiss in replication technique and reach an on-axis resolution of better than 30 arcseconds. The focal planes of the seven telescopes share a 6 cm by 6 cm monolithic CCD detector of pn type developed by MPE and IAAT. It is nearly identical to that used for the XMM/EPIC camera and has the main advantages of high quantum efficiency and short readout cycles.

The tight ABRIXAS program schedule requires 250 mirror shells to be produced, checked and accepted within one year. This means that the fabrication processes have to be fully understood and kept completely under control. This applies mainly for the major production steps, like gold-coating of the mandrels, Nickel electroforming, mirror shells release from the mandrels and mirror shells testing and acceptance. We will report about the way how we tackled these technical and logistic challenges. Another important step for the optical performance of ABRIXAS Mirror Modules is the integration of the 27 mirror shells in the structural parts. This process requires high skill and good control means, like optical collimator, CCD camera and sophisticated analysis tools in order to achieve optimal-co-alignment of the 27 mirror shells axes and best confocality. This is guaranteed by dedicated test-facilities and sophisticated analyses software. We will report about the results obtained on integrated single mirrors shells as well as on the assembly of all 27 mirror shells.

ABRIXAS stands for 'A Broadband Imaging X-ray All-Sky Survey'. Its launch is scheduled for spring 1999, it shall perform, thanks to its special design, an efficient all-sky survey at high photon energies, thus continuing ROSATs successful work in an extended energy band. We will report here about the design and development activities for the ABRIXAS Mirror System.

ABRIXAS is a German satellite project - to be launched in spring 1999 - which will perform the first imaging x-ray all-sky survey in the 0.5-10 keV band thus being a complement to the ROSAT all-sky which covered the 0.1-2.4 keV range. Its telescope consists of seven mirrors modules, each with a diameter of 16 cm and a focal length of 160 cm. the mirror modules are tested and calibrated at the MPE X- ray test facility PANTER. Several mirrors from the qualification program and one flight module have been tested and calibrated up to now. The imaging performance of the optics was successively improved until the flight module reached an on-axis resolution of 22 arcseconds. The total scattering level at 8 keV is about 16 percent for two reflections which indicates a microroughness of less than 0.5 nm. The measured on-axis effective area of one flight mirror module is 81 cm² at 1.5 keV and 25 cm² at 8 keV. These values indicate that the reflectivities of the mirror surface are on the average about 92 percent of the theoretical expectation.

We describe a method of building and deploying an ultra high throughput x-ray observatory with 2 by 10⁵ cm² of effective area for the era following the Constellation X-ray Mission and XEUS. It is based upon a single focus telescope. Replacing and adding detectors are possible. Instead of an optical bench, the detector uses electric propulsion with plasma thrusters and ion engines to maintain its station at the focus and repositioning itself for new targets. The preferred site is the L2 point; a high circular orbit is also possible. Additional or replacement detectors equipped with ion/plasma engines are launched on much smaller rockets and rendez-vous with the telescope. We describe how such a telescope with an angular resolution of a few arcseconds could be fabricated. As an example, we consider a 7 m X 7 m aperture, 100 m focal length standard Kirkpatrick-Baez optic. It is segmented into several hundred modules of identical size. A co-aligned group of segments is equipped with a fiducial and a positioning system for alignment to a common focus in space. With subdivided reflector substrates made from light weight advanced composite materials the launch mass of the telescope spacecraft is within the capability of current vehicles.

Future x-ray space missions will require high throughput x- ray telescopes with angular resolution of the order of tens arcsec and large effective area. Nowadays the most used technology to obtain thin and light mirror shells is the replica technique by nickel electroforming. This technology has been successfully employed for projects like SAX, JET-X, XMM and ABRIXAS. Nevertheless the high density of the nickel poses some limitations to the possibility of extending the use of this technology for future x-ray space missions. In this respect the use of ceramic materials like silicon carbide and alumina for the manufacturing of x-ray optics appears to be an attractive technology. In the paper we review possible processes for manufacturing x-ray mirror shells using silicon carbide ceramic material and we report the result of an on-going activity aimed to verify the performances of these new technologies in the context of the wide angle x-ray survey project. This is a small satellite mission aimed to survey a large part of the sky in the x-ray band. The project is being developed as a feasibility study in the frame of the Agenzia Spaziale Italiana program for small-medium satellite missions.

Lobster-eye optics have been proposed as an exciting development in the field of x-ray all-sky monitors. However, to date their potential has mainly been analyzed in the context of an all-sky monitor for a small satellite mission. We examine the wide range of parameters available for lobster-eye optics with different configurations. The sensitivity of the various schemes is calculated. We have also examined the current state of the art in actual lobster-eye optics. We present our experimental results and discuss realistic targets for manufacture. The impact of these targets on the calculated sensitivities is also described.

The concept of the lobster eye optics was proposed in the nineteen seventies. It has gained widespread interest in x- ray astronomy for its potential for constructing compact and focusing x-ray all sky monitors with unprecedented sensitivities. The majority of the efforts of developing a practical implementation of this optics has been devoted toward slumping square-pore micro-channel plates. While the advantages of the slumped micro-channel plates are obvious in that they can achieve potentially arc-second angular resolutions, the smoothness requirements for reflecting x- rays are hard to meet by micro-channel plates. It is not clear how the interior of the micro-channel plate pores can be polished to the desired smoothness. In this paper we propose the feasibility of a more straightforward approach of implementing the lobster eye optics with flat glass mirrors assembled in a standard Kirkpatrick-Baez configuration. We demonstrate with both simulations and laboratory test results that this implementation is both practical and meets al the requirements of an x-ray all sky monitor.

The latest achievements in manufacturing and investigations of polycapillary optics in Russia are reviewed. For the first time one succeeded in creating the polycapillary lens with focal spot diameter lesser than 10 micrometers . Combination of these lenses with a small portable microfocus source of 100 W power allows to obtain the x-ray photons concentration more than 10⁵ photons/s micrometers ². Such density is comparable with density obtaining at the synchrotron beams with E equals 1 GeV and 0.1 A current. This result is a revolutionary one for a number of applications, e.g., for diffractometry, x-ray analysis, x-ray microscopy, etc. On the base of a halflens and new 10 W microfocus tube of 10 micrometers size the space-saving source emitting parallel x-rays with brightness of the order of 10¹⁰ photons/s mm² had been created.

In this paper a new method of micro-XRF will be presented. A polycapillary conic structure was used for collimation of the fluorescence radiation emitted by the sample. In spite of the usual method for realization of local analysis, in which the primary beam has to be collimated on the sample surface, the polycapillary conic collimator takes the fluorescence radiation from a local area and transports it to the detector. Under these conditions the primary beam may irradiate a large surface area at the sample. Therefore, also X-ray sources of moderate brilliance may be used in such an experimental set-up. A spatial resolution of about 20 micrometers can be achieved.

A novel type of vacuum window for application in the soft energy range is proposed, namely: a polycapillary structure with millions of individual channels. This structure has low vacuum conductance and is transparent to x-ray radiation. Vacuum and x-ray transmission properties are investigated both theoretically and experimentally. Possible applications are considered.

The use of Kumakhov optics in x-ray fluorescence analysis is considered. Thanks to high efficiency of a polycapillary lens the concentration of x-ray detector in a close proximity to the sample decreases sufficiently the time of exposure. It is shown experimentally that in the case of use of a small x-ray source with power of 2W the minimal detection limit may be of the order of 0.1 pg. A new portable x-ray fluorescence analyzer based on Kumakhov optics is described. Minimal detection limit may achieve 10^-16 g if 100 W microfocus source and the lens with approximately 10 micrometers focal spot are used.

A monolithic polycapillary optic was coupled with a mini focus x-ray source. The convergent beam of this system was used for micro fluorescence an was compared to a rotating anode source. The fluorescence intensities obtained from identical samples have been compared. Monolithic polycapillary x-ray optics can collect x-rays from mini and micro focus sources over a large solid angle and refocus them outside of the tube envelope into a small spot several tens of microns large. The intensity gain of such a system can exceed tow orders of magnitudes. This makes it possible to obtain intensities comparable or larger than available with common high intensity rotating anode sources. The smaller size, lower cost, ease of use and immediate availability of the Oxford mini focus source, makes it an attractive option for a variety of microanalysis applications.

Possibility of creating the x-ray telescope with use of polycapillary optics have been discussed during approximately ten years. However, only later this idea is getting reality owing to the improvement of manufacturing technology. Possibility of creating the telescope for a broad energy range is considered. For choice an optimal version of the telescope the experiments on transmission the x-ray beams of different energies through polycapillaries with channel diameters from 0.5 micrometers up to 30 micrometers carried out. As basic module the version of telescope with 100 sq.cm entrance area and focal distance from 1 to 2 meters is considered. For improvement of the angular resolution of proposes to arrange the polycapillary collimator with angular resolution of the order of 10^-4 a radian before the telescope.

A prototype capillary optical system has been developed to further test the possible use of polycapillary optics for a hard x-ray spectrometer for astrophysical applications. It has been evaluated both as a concentrator and a collimator of x-rays with energies between 10 and 60 keV. Transmission efficiency, angular acceptance and focal spot size have been measured. Both experiment and simulation results for the prototype optic have demonstrated the potential of x-ray polycapillary optics for astrophysical applications. Further design and fabrication improvements indicated by prototype studies are discussed.

The research x-ray system, having no analogues in the world, have ben created in IRO. The minisystem with x-ray optical system, consisting of the focusing lens and halflens, allows to perform, without changing a sample orientation, the fluorescence element analysis of the sample, and also phase analysis, determination of stress, texture of sample, etc., by means of diffraction methods with use of collimated x-ray beam from the halflens. The use of specially developed small x-ray tubes, generators, software, and possibilities of the research system application in a various fields are discussed.

In this work transmission of soft x-rays by separate capillaries under focusing geometry is considered. It is shown that a part of synchrotron radiation beam is 'captured' into regime of a mode transmission under spreading into channels. A superposition picture for x-rays at focal plane confirms a wave character of spreading for beam definite part. The experimental and theoretical data are presented. The outlooks for using mode character of transmission for developing x-rays optics and creating new devices are discussed.

The results on bending of synchrotron radiation beam over large angles by means of capillary structures are presented. A possibility of beam bending not only on plane of electron orbit, but also a possibility of x-ray beam leading out a horizontal plane of the accelerator is shown. In the report a problem of synchrotron radiation polarization is discussed. A comparative analysis of the result of computer simulations and experiments is given.

The use of Kumakhov halflenses in a small diffractometers with position-sensitive detector for the investigation of stress-deformation state is considered. The possibility of obtaining the system of parallel beam with a small angular divergence allows to estimate the state of stress- deformation in a various sections of object under investigation, owing to drawing near or moving away x-ray tube connected with the halflens. It is shown, that the new method should be very interesting for determination of the reliability of a real articles.

A new generation of sub-micron soft x-ray filters has been developed for use in solar astronomy. These filters are designed to achieve higher transmission than is currently available in the wavelength region from 40 angstrom to 170 angstrom. Prototype filters have been fabricated using advanced deposition techniques, and utilizing multilayer combinations of materials to optimize performance in the spectral region of interest. Zirconium, niobium, palladium, and rhodium have been fabricated as prototype materials, both as singular foils and in multilayer combinations with polyimide as a support film. Results discussed include visible light rejection, accelerated life testing and x-ray transmission.

In this paper a new system is proposed which allow to obtain monochromatic x-radiation of high intensity in a small sized focal spot. It consists of straight monocapillaries combined with mosaic graphite crystals. The capillaries at the entrance side of transport x-radiation from the source to the graphite crystals where it will be monochromatized due to the Bragg effect. A second set of capillaries collect the monochromatized radiation and focus it in a small focal spot. An intensity gain is realized by a parallel radiation transport through many capillaries arranged symmetrically around the optical axis of the system. Testing results of this monochromatizing concentrator for the Mo-K(alpha) line are presented in this paper. A multiple intensity gain of this line is achieved in comparison with the direct x-ray beam.

Non-intuitive surface scatter effects resulting from practical optical fabrication tolerances frequently dominate both diffraction effects and geometrical aberrations in high resolution grazing incidence x-ray telescopes. The resulting reduction optical performance due to scattering is a strong function of x-ray energy, residual surface characteristics, incident angle, and the optical performance criterion appropriate to the application. A simple Fourier treatment of surface scatter phenomena, based upon a non-paraxial scalar diffraction theory, is referenced and utilized to produce parametric performance predictions that provide physical insight and understanding into the surface scatter phenomenon and its effect upon image quality. The optical prescription for the Solar X-ray Imager will be used as an example.

It is well known that normal incidence, aplanatic telescope designs performed better at low field angles than ones corrected only for spherical aberration. This is why most large astronomical telescopes fabricated in the past fifty years have been of the Ritchey-Chretien design rather than of the classical Cassegrain design. For the relatively new field of x-ray/EUV astronomy, the Wolter type-I and Wolter Type-II grazing incidence designs have been extensively utilized. Both types consist of a paraboloidal primary mirror coaxial with a confocal hyperboloidal secondary mirror.The Wolter Type-II is the grazing incidence analog of the classical Cassegrain design. 'Aplanatic' versions of both the Wolter Type-I and the Wolter Type-II grazing incidence x-ray/EUV telescopes have been discussed in detail in the literature, and are widely touted as being superior designs. And indeed they are, at small field angles where coma-like aberrations dominate astigmatism-like ones. However, scattering effects and other practical optical fabrication tolerances prevent these grazing incidence telescope designs from being near diffraction-limited at the x-ray/EUV wavelengths, even on-axis. Since the scattering effects dominate residual coma-like design errors at the small field angles, there is negligible improvement in performance and perhaps a significant disadvantage in cost and schedule of fabrication. Comparison of performance predictions for the classical versus 'aplanatic' Wolter Type-I x-ray telescopes will be presented for the special case of the solar x-ray imager. SXI is a soft x-ray, solar telescope which is expected to become a standard subsystem aboard the next generation of NOAA/GOES weather satellites.

We report a study of the residual stresses and residual stress relaxation in Mo/Si and Mo₂C/Si EUV multilayers. The multilayers were fabricated by magnetron sputter deposition, and stress measured using the substrate curvature laser scanning technique. It was found that Mo₂C/Si multilayers exhibit higher compressive stress than Mo/Si of comparable period and layer thickness ratio. The multilayers sputtered at 0.5 mT Ar pressure have higher compressive stress than those sputtered at 2 mT Ar pressure. The data indicate that the residual stresses in the multilayers are primarily determined by the Si layers. Annealing of the multilayers at a heating rate of 5 degrees C/minute as well as at a fixed temperature results in a reduction of the compressive stresses. Near zero stress is achieved after annealing at 300 degrees C. The time dependence of the residual stress decrease during isothermal annealing was found to fit best to a bimolecular viscous flow model of defect annihilation in the amorphous Si layers. The relationships between the effects of annealing on the multilayer microstructure and the observed stress reduction are discussed.

We are engaged in a program to develop focusing hard x-ray optics for future x-ray astronomy missions. Optics are being developed to focus x-rays up to and beyond 80 keV. Emphasis is on the multilayer coating of integral cylindrical optics which will provide the highest spatial resolution. A chamber geometry has been designed to allow the uniform coating of the inside surface of integral cylinders. The building and testing of this system has taken place over the past year. Linear DC magnetron cathodes are used to sputter the multilayer films. Initial results from both longitudinal and azimuthal uniformity coating tests are presented.

The Multilayer Facility at the Center for Astrophysics is involved in developing graded-d spacing multilayers for coating X-ray optics for hard x-ray focusing telescopes. Graded d spacing W/C multilayers have been fabricated on flat substrates of silicon and characterized using specular x-ray reflectivity, AFM, and TEM. Results are presented and compared with theoretical models.

Studies are being carried out to compare the performance of several different separation materials used in the replication process. This report presents the results obtained during the second year of a program which consists of replicating smooth, thin substrates, depositing multilayer coatings upon them, and evaluating their performance. Replication smooth, thin substrates, depositing multilayer coatings upon them, and evaluating their performance. Replication and multilayer coatings are both critically important to the development of focussing hard x- ray telescopes that function up to 100 keV. The activities of the current year include extending the comparison between sputtered amorphous carbon and evaporated gold to include sputtered as well as evaporated gold. The figure of merit being the smoothness of the replica which has a direct effect on the specular reflectivity. These results were obtained with epoxy replication, but they should be applicable to electroformed nickel, the process we expect to use for the ultimate replicated optics.

We present a current status of the development of hard x-ray telescope using Pt/C multilayer supermirror. The telescope system is to be made by combining thin foil replication technology for high throughput mirror and multilayer supermirror coating technology for hard x-ray reflection. After the successful multilayer coating on the replica foil mirror, we made the performance demonstration model of this type of telescope, having 20 replica foil supermirrors, 10 primary and 10 secondary reflectors, with focal length of 4.75 m and radius of 100 mm. Pt/C multilayer supermirror structure was designed and optimized to have high and flat reflectivity for x-ray energy from 25 through 40 keV. After some efforts to avoid heat damage of replica foil mirror during the deposition process of multilayer by DC sputtering system, we could establish the fabrication method of supermirror structure on replica foil mirror. Based on the x-ray measurement, we found that this demonstration model showed the half power diameter of 1.9 arcmin for had x-rays and nearly the same reflectivity and energy band width as expected. In this paper, we present the design of graded multilayer as the supermirror, the fabrication and the performance of this demonstration model.

In the fabrication of the x-ray reflector using the replication method, Au was thought as the only material which can be used as the surface of reflector. However, if we could use the Pt or Ir, these has higher electron density than Au, as the surface, we can obtain higher reflectivity especially in the hard x-ray band. Furthermore, direct replication of the multilayer is very useful for the high reflectivity and mass-production process. We used the Au replica foil as the substrate of the multilayer. However, the epoxy layer of the replica foil was easily damaged by the heat during the deposition. This is a serious problem for the mass-production process, since we must take a long time to deposit the multilayer to keep the high reflectivity. We studied the direct replication of the multilayer, and successes to obtain the reflectivity as high as original one. Furthermore, we keep the trying to improve the quality of the reflector as flight quality. We will report the results and feature prospects of the replication of the multilayer and its application to the hard x-ray telescope.

We discuss the development of beamline U3A at NSLS for AXAF telescope witness mirror reflectivity calibrations in the 1- 2 keV energy range. The beamline was originally constructed as a white light beamline and has been upgraded with the addition of a monochromator to meet the needs of the AXAF calibration program. The beamline consists of an upstream horizontally focussing gold coated elliptical mirror, a differential pumping section, a sample/filter chamber, a monochromator and a downstream filter set. The mirror is set at a 2 degree incident angle for a nominal high energy cutoff at 2 keV. The monochromator is a separated element, scanning, double crystal/multilayer design having low to moderate energy resolution. A fixed exit beam is maintained through the 7-70 degree Bragg angle range by longitudinal translation of the second scanning crystal. Tracking is achieved by computer control of the scan motors with lookup table positioning of the crystal rotary tables. All motors are in vacuum and there are no motional feedthroughs. Several different multilayer or crystal pairs are co-mounted on the monochromator crystal holders and can be exchanged in situ. Currently installed are a W/Si multilayer pair, beryl, and Na-(beta) alumina allowing energy coverage from 180 eV to 2000 eV. Measurements with Na-(beta) alumina and beryl show that beam impurity less than 0.1 percent can be achieved in the 1-2 keV energy range. Measured resolving powers are E/(Delta) E equals 60 for W/Si, 500-800 for (beta) alumina and 1500 to 3000 for beryl. Initial results suggest that signal to noise and beam purity are adequate in the 1-2 keV region to achieve the 1 percent calibration accuracy required by AXAF. This allows overlap of Ir MV edge data taken on x-ray beamline X8A and with low energy data taken on ALS beamline 6.3.2.

We present the first results of pre-flight calibrations of the x-ray telescopes on board ASTRO-E satellite. They adopt a thin foil-nesting Wolter Type-I optics, which is in principle the same as ASCA XRTs. Owing to a scale up of the telescope and a new technique of the reflector production, however, both the effective area and the imaging capability are improved. In the current measurements, the effective area is obtained to be 460, 313 and 250 cm² per XRT at 1.49, 4.51, and 8.04 keV, respectively, which is significantly larger than that of ASCA by a factor of 1.5 and 2.5 at 1.49 keV and 8.04 keV. The point spread function also shows a better focusing capability than ASCA by a factor of 2, and the half power diameter is obtained to be 1.84 arcmin at 4.51 keV. The brightness of the stray light is obtained to be 2 X 10^-5 counts s^-1 mm^-2 at the brightest part of the stray light image, in the case that the x-ray star with the on-axis intensity of 1 count s^-1 is the source of the stray lights, which is almost the same with ASCA.

The Physikalisch-Technische Bundesanstalt (PTB), Germany's national metrology institute, has been operating a radiometry laboratory at the BESSY I 800 MeV electron storage ring since 1982. The BESSY I electron storage ring is optimized for radiometry and is used as a primary source standard with calculable spectral photon flux with relative uncertainties below 0.4 percent. A cryogenic electrical- substitution radiometer is used as a primary detector standard with a relative uncertainty in the determination of the radiant power of about 0.2 percent. Various experimental stations allow for the use of undispersed, calculable synchrotron radiation from bending magnets up to a photon energy of 15 keV and of monochromatorized synchrotron radiation in the 3 eV to 1500 eV spectral range, respectively. Major activities comprise the calibration of radiation detectors rand radiation sources as well as the characterization of optical components in the VUV and soft x-ray spectral range with low uncertainty. Among radiometric calibrations for different applications, extended work has been performed for solar and astronomical missions like SOHO, AXAF and XMM.

We describe a fast figure metrology system designed for the several thousand mirror quadrants in the High Energy Focusing Telescope (HEFT) balloon experiment. HEFT's multilayer coated hard x-ray optics will have approximately 1 arcminute HEW and operate at 20-80 keV. The optics are a conical approximation to the Wolter I configuration. Our automated system can measure the axial figure error, in- phase and out-of-phase roundness errors of a mirror quadrant, and output their HEW contribution to the x-ray telescope. An optical laser scans a conical mirror in two cylindrical coordinate axes. A 2D position sensitive diode measures the reflected beam to approximately 4 arcseconds. The conical mirror can have >= 3 cm radius. We show the figure measurements of HEFT's aluminum foil and thermally formed glass substrates.

The optical scheme of grazing incidence monochromator with concave grating with variable space is offered. The monochromator has a simplified kinematic scheme of spectrum scanning mechanism. Scanning is obtained by turning the exit slit and grating, fixed with each other relatively to the axis that goes through the vertex of the concave grating while enter slit is fixed. Kinematic scheme provides change of grazing incidence angle and constant grazing angle of diffraction. Moreover, increase of grazing incidence angle affects an increase of the wave length. In this case shorter wave length radiation diffracts on the grating with more losses. This results in decrease of the highest spectrum orders, being not preferable. The well-known schemes on the Rowland circle have an entrance slit with significant linear motion, which makes the construction more complicated. Those conditions for changing the incidence and diffraction angles are not accepted in monochromators of constant angle of deviation.

Polycapillary x-ray optics, arrays of hollow capillary tubes used to guide x-rays by total reflectance, are now being used in increasing numbers of applications, such as materials analysis, microelectronics manufacturing, x-ray astronomy and medical imaging. Because each optic contains hundreds of thousands of precisely shaped and located hollow channels, it is desirable to assess the feasibility of a variety of capillary geometries for a new application without physically constructing the optic. This assessment requires increasingly sophisticated modeling capability as new applications with more stringent requirements are developed. Previous analysis has shown that high-energy applications such as hard x-ray astronomy and medical imaging are particularly sensitive to optic profile errors such as channel waviness. A more physical model for surface waviness has been developed and included in optics simulations. The results are compared to measured data and to the results of other numerical simulation programs.

Mo/B₄C is chosen for the materials of the multilayer mirrors for 7.3nm and 8.0nm. The structural parameter has been designed and the mirrors has been fabricated by magnetron sputtering. Details in the microstructure of Mo/B₄C multilayer were revealed using x-ray diffraction and TEM. The period thickness of each mirrors can be determined from the curve of x-ray diffraction, and they are 3.74nm and 4.12nm, respectively, which are in good agreement with the design parameters.

The collect of capillaries into polycapillaries and x-ray lenses offers many possibilities in several scientific fields: physic, astronomy, industry, medical imaging. Before buying and using a system based on capillaries, one needs to simulate the performance of various kinds of x-ray optics. In order to predict the behavior of such optical system a simulation program has been developed to test all kinds of capillary optics available on the market. This report is exhibiting theoretical methods used to assess transmission, exit divergence and image obtained behind a polycapillary just as an x-ray lens. The simulation program can test many kinds of optics based on capillaries in the energy range 1- 80 keV. Some experimental comparisons have been achieve din order to guarantee the validity of our simulation result. By means of this simulation program, one can optimize an x-ray lens to put in an optical chain with respect to experimental conditions and restraints.

This paper describes the design and the successful integration of the optical block of the SODART telescopes to be flown on the Spectrum Roentgen Gamma satellite. The integration involves both the integration of the two high throughput x-ray telescopes as well as the objective crystal spectrometer. The integrated unit meets all mechanical, thermal and optical specifications and it is now in safe storage in Moscow and awaits further integration procedures with the remaining satellite structure.

We have developed a comprehensive model of the response of a CCD to soft x-ray illumination. The model is based on the Monte Carlo technique and follows the interactions with the device material of individual photons thrown into the structure, calculating device reaction to each of them. It incorporates a very detailed description of the CCD gate structure, as well as accurately measured absorption coefficients. The fluorescent and escape peak model takes into account interactions inside the gate structure, which dramatically improves the agreement with the experimental data at energies close to the Si absorption edge. The shape of the low energy tail is simulated according to our new model of electron cloud charge splitting at the interface between Si and SiO₂. An origin of the tail in the horizontally split events is explained as coming from the p+ area in the channel stop region and is modeled accordingly.

A new DC magnetron sputtering facility has been build up at the Danish Space Research Institute, specially designed to enable uniform coatings of large area curved optics, such as Wolter-I mirror optics used in space telescopes and curved optics used in synchrotron radiation facilities. The paper is a brief description of this new facility and the future applications.

Johann and DuMond quartz crystal focusing spectrometers are proposed for hard x-ray spectra investigations of sub-ps laser-produced plasmas when the source is located on the focal circle. Because the crystal intercepts and focuses a large solid angle of radiation, the schemes have extremely high efficiency, which could be 10³ times higher than those of flat crystal spectrometers. Due to the small size of the source the schemes have a high spectral resolution. By using reflection and transmission modes, the schemes cover a very wide spectral range: 0.2-2.3 angstrom. Curved quartz crystal is tested in the reflection mode using Fe K_(alpha ) radiation.