We report on results of a comparative study of two reflection techniques, Bragg diffraction from mosaic crystals and reflection from continuously graded multilayers, presently under development to focus hard x rays for astronomical applications. Particular emphasis is given to compare the performance of Wolter I telescope configurations based on multilayers coatings with paraboloidal telescope configurations based on mosaic crystals of graphite (002), that are currently under investigation in our group.

We report investigations of the x-ray focusing of a square channel capillary array. We use x rays with an energy of about 1.5 keV from a laser produced plasma. We find the focal structure to be consistent with theoretical expectations. The images were recorded using x-ray film and, to within the precision with which we were able to analyze the results, the data is consistent with an array with negligible channel tilt and a surface roughness of 1.5 nm rms. This is the best performance yet reported for lobster-eye x-ray optics.

A slice of ordinary multilayer structure represents a miniature sample cut out of layered media which can be used as a reflection or a transmission grating. The analysis shows very high flexibility of these gratings. Various properties can be achieved by proper design and choice of layer materials: (a) high angular dispersion due to submicron grating period, (b) high throughput in XUV range due to resonance Bragg effect, (c) high spectral resolution defined by the number of layer pairs in a sample (up to 1000), (d) focusing properties achieved by grading of multilayer period which is introduced in the process of deposition. The present status of research on reflection sliced multilayer grating is presented. If the multilayer coating is deposited onto a wire of submillimeter diameter then the slice of it represents a zone plate if the Fresnel law of layer thickness variation is provided. This sputter slice method is known to be a prospective technology for production of zone plates with increased diffraction efficiency, spectral selectivity and spatial resolution. The physical reason for it is the strong interaction of incident radiation with layered media which takes place in optically thick zone plates. The wave theory of high aspect ratio zone plates is given with the emphasis on practical design. The software capable to simulate diffraction characteristics of realistic zone plates, to calculate and visualize the global field distribution, optimize materials and geometry of zone plate is being developed.

The Joint European X-ray Telescope, JET-X, is one of the core instruments of the scientific payload of the Russian SPECTRUM-X astrophysics mission. Jet-X is designed to study the emission from x-ray sources in the band of 0.3 - 10 KeV; particularly to meet primary scientific goals in cosmology and extragalactic astronomy. JET-X consists of two identical, coaligned x-ray telescopes, each with a spatial resolution of 30 arcsecond half energy width (HEW) or better. Focal plane imaging is provided by cooled x-ray sensitive CCD detectors which will combine high spatial resolution with good spectral resolution, with particular emphasis on high sensitivity and spectral resolution around the 7 KeV Fe-line complex. Each telescope is composed of a nested array of 12 mirrors with an aperture of 0.3 m and focal length of 3.5 m; the total effective area is 360 cm² at 1.5 KeV and 140 cm² at 8 KeV. The mirror shells have a Wolter I geometry and are manufactured by a nickel electroforming replica process. The paper presents a status report of the qualification model of the x-ray optics.

The optical system requirements for high throughput, high resolution, x-ray telescopes for future space missions that foresee the use of a manufacturing process by replica method, demand a tight control of the shape of the mandrels used for the production of the shells. Since the number of mandrels to be manufactured for a project is generally high, it's also important that the technology adopted for the shape control be cost-effective. With the proposed approach, the aluminum-kanigen mandrels are diamond turned and superpolished to the required microroughness. The final figuring is then obtained with the ion-beam polishing technology that allows the fine tuning of the mandrel shape preserving its microroughness. This method has significant advantages over other conventional figuring processes since no physical load is applied to the mandrel and the material removal function generated from the ion source is stable and repeatable, allowing a deterministic final figuring in one or few passes. A computer simulation of the ion-beam polishing of a mandrel has been executed. An evaluation of the effect of the size of the material removal function used, the final surface error, and the working time required have been obtained.

For the last decade we have been developing conical approximation of the Wolter I type thin foil/shell grazing incidence x-ray mirrors. Several missions have come out of these developments, e.g., BBXRT, and Astro-D (a U.S. - Japanese collaboration now known as ASCA), and Sodart on board SPECTRUM-X-GAMMA in the near future. The spatial resolution of this type of telescope is an order of magnitude worse than the theoretical limit, which hosts a great potential of improving these high throughput and relatively inexpensive x- ray instruments. In summary, x-ray image can be improved by reducing surface roughness and profile error for specularly reflecting x-rays in a better defined direction. The conventional way, coating reflecting surface of substrates with a thin layer of acrylic lacquer, was not effective in smoothing the surface roughness in spatial wavelength longer than a few microns. The profile of the foils was controlled by forming the substrate under certain mechanical pressure and/or combining heat treatment, but very often, the process is detrimental to the surface quality of roughness in millimeter wavelength. We report a new development of using epoxy replication technique on smooth pyrex mandrels. The results show very encouraging improvements over the conventional method. The half power diameter (HPD) of the x-ray image has dropped from 3.5 arcmins to 1.0 arcmin, and the extended image blur, i.e. the tail part of the encircled energy function (EEF), which was attributed to the roughness at higher spatial frequencies, was drastically reduced by 10 times. In this report we summarize the new technique in progress and the direction for future development.

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 telescopes coupled to reflection grating spectrometers and x-ray CCD cameras. Each XMM telescope consists of 58 Wolter I mirrors that are replicated from superpolished nickel coated mandrels. The mirror figure and finish specifications are tight and therefore it is essential to assess the surface quality of the mandrels. This is done in the workshop by a metrology system involving different profilometers. However, the performance of a mandrel can also be directly determined with x-ray tests that allow the user to verify the measurements of the workshop instruments. The ESRF synchrotron storage ring produces x-ray beams of very high quality and has a beamline dedicated to high resolution tests of x-ray optical components. One XMM mandrel was characterized on this beamline by a three axis x-ray scattering technique. Power spectral density functions and profile slopes were derived from the x-ray measurements and compared to those determined by the metrology instruments. The present paper describes the x-ray experiment and discusses its results in the context of the XMM mandrel manufacturing program.

History of the multiple reflection optics evolution is considered. Characteristics of a capillary x-ray optical system are presented. Various applications of these systems are described.

Special methods of experimental investigation of x-ray polycapillary x-ray lenses are elaborated. A large number of x-ray lenses were investigated due to these methods. The results of investigations prove high efficiency of produced lenses.

Kumakhov semilens work for quasiparallel x-ray beams transformation into convergent ones was numerically studied. The role of semilens geometry, x-ray beam energy, capillary diameters, initial radiation divergence and the influence of these factors on semilens transmission and focal spot forming were investigated.

In the paper a theoretical model for calculation of x-ray photon characteristics under passage through capillary systems is described. The model is based on a numerical solution of a wave equation. It is shown that recently discovered interference effect under multiple reflection of x rays is an evidence of wave properties of x rays. In this report an explanation of the observed phenomenon is given.

We have produced two new normal incidence soft x-ray telescope mirrors coated for lambda equals 63.5 angstrom wavelength: the first with a focal length f equals 1.5 m and a diameter of 25 cm for the Space Weather and Terrestrial Hazards (SWATH) satellite and the second (f equals 2 m, diameter 27.5 cm) for launch by sounding rocket (NIXT). We describe figuring and polishing of the mirror surfaces and deposition and testing of the multilayer coatings. Optimization of the mirror fabrication included grazing incidence x-ray reflectivity for quality control during polishing. In addition, the substrate and each metal layer of the Co-C multilayer coating were polished by an ion beam with in-situ roughness estimation. We explored the possibilities and limitations of telescopes for shorter wavelengths by coating several small mirrors covering the lambda equals 45 to 60 angstrom region at normal incidence and report on their performance.

We present an approach to obtaining a modular hard x-ray Wolter-I type telescope based on combining present replication technologies, for complete sub-arc minute cylindrical shells, with deposition of Ni/C broad-band hard x-ray multilayers. Based on a combination of literature review, stress measurement, modelling, and characterization of a number of replica and non-replica optics using AFM, interferometry and grazing incidence reflection, we conclude that (1) it should be possible to fabricate sputter targets small enough to coat the inside of approximately equals 10 cm diameter shells (2) in spite of the large Ni/C multilayer stresses, calculations show that the structural integrity of the complete shells limit the deformation to less than 1% of the surface and; (3) the quality of multilayers coated on replicas with gold surfaces, is not as good as those coated on standard substrates. The mediocre quality is found to correlate with a large degree of roughness on nanometer length scales, which is most likely a result of the previously well-documented polycrystallinity of gold films. The mediocre quality of the multilayers on replicas would lead to a 2-fold reduction in the effective area.

Molibdenum-silicon multilayer structure as a soft x-ray mirror fabricated using a magnetron sputtering system has been studied through x-ray diffraction (XRD) of Cu K_(alpha ) (1.54 angstrom) radiation. The angular positions, the relative intensities, the widths of Bragg primary and secondary peaks in XRD pattern are sensitive to structural parameters such as unit thickness (bi-layer thickness), thickness ratio of composite materials, diffusion lengths, and roughness. Effects of each structural parameter on XRD pattern have been investigated. The results show that the angular positions of Bragg primary peaks are sensitive to the bi-layer thickness, the pattern of secondary peaks is sensitive to the thickness ratio. It is also found that the major effect of interfacial diffusion is the reduction of the intensities of high-order Bragg primary peaks, and roughness is responsible for the broadening of the widths of Bragg primary peaks and the increase of the intensities of Bragg secondary maxima. Using the above results, we have analyzed experimental XRD data to draw the structural parameters of Molibdenum-silicon multilayer structure.

Optical constant determination of thin films is critical to the design of x-ray multilayers. In the x-ray region, surface roughness, interfacial roughness, interdiffusion, volume anisotropies, etc. all act to reduce the reflectance. Reflectance measurements were taken at NIST in Gaithersburg, MD. From these measurements the optical behavior results of a substrate, single films and two film combinations were determined by best fitting the measured reflectance values as a function of the angles of incidence with a functional form based on the theoretical reflectance as a function of the optical constants. By using these new optical constants in a multilayer design, the performance of a multilayer can be predicted.

The Multi Spectral Solar Telescope Array (MSSTA) is a rocket borne observatory that utilizes an array of multi-layer and interference film coated telescopes to observe the solar atmosphere from the chromosphere to the corona, over a broad spectral range (VUV - soft x rays). The MSSTA is continuously evolved to incorporate new instruments, and to improve its ability to investigate specific topics related to the structure and dynamics of the solar atmosphere. We describe chromospheric and coronal observations recorded during the second flight of the MSSTA on November 3, 1994 at 1915 UT.

We carried out experiments to determine the optimum parameters for the production of multilayer x-ray mirrors for the lambda equals 4.4 - 7.1 nm range using electron beam evaporation and ion-polishing. We report on the deposition of Co/C and Ni/C coatings, of which we polished the metal layers with Kr⁺- and Ar⁺- ions of 300, 500, and 1000 eV. We examined the effect of different polishing parameters on the smoothening of the Co- and Ni-layers. The in-situ reflectivity of lambda equals 3.16 nm during deposition and the ex-situ grazing incidence reflectivity of Cu-K_(alpha ) radiation (lambda equals 0.154 nm) were used to analyze the coatings. We found optimum performance of the mirrors when applying polishing for 40 s with 500 eV Kr⁺-ions at an angle of 20 degrees and an ion beam current of 20 mA. Using these parameters, we produced Co/C multilayer coatings on forty flat super-polished 6 multiplied by 6 cm² Si (111) crystals for the Objective Crystal Spectrometer on the Russian Spectrum Rontgen Gamma satellite. The coatings on the flight crystals have a period Lambda of 3.95 plus or minus 0.02 nm and a reflectivity of more than 8% averaged over s- and p-polarization over the entire wavelength range of interest. We present a detailed analysis of the coatings on the crystals.

Thermal stability of structure, period and x-ray reflectivity of multilayer mirrors for the whole range of soft x rays with wavelengths 1 - 30 nm were studied in wide temperature range 350 - 1400 K by x-ray scattering and cross-sectional electron microscopy methods. Irradiation by He⁺ particles with energy 30 keV and doses 1 multiplied by 10¹⁹ -4 multiplied by 10²⁰ ion/m² and by 10 MeV-electrons with dose up to 10^-4 Gray was carried out for evaluation of radiation stability of Mo/Si and MoSi₂Si multilayer mirrors. It was shown that thermodynamic equilibrium of layer materials at their interfaces and stabilization of layer structure by impurities and heat treatment are an effective approach to multilayer x-ray optics with enhanced thermal and radiation stability.

We set forth a conceptual design for an x-ray all-sky monitor based on lobster-eye wide-field telescopes. This instrument, suitable for a small satellite, would monitor the flux of objects as faint as 2 multiplied by 10^-12 erg cm^-2 s^-1 (0.5 - 2.4 keV) on a daily basis with a signal-to-noise of 5. Sources would be located to 1 - 2 arc- minutes. Detailed simulations show that crosstalk from the cruciform lobster images would not significantly compromise performance. At this sensitivity limit, we could monitor not just x- ray binaries but fainter classes of x-ray sources. Hundreds of active galactic nuclei, coronal sources, and cataclysmic variables could be tracked on a daily basis. Large numbers of fast transients should be visible, including gamma-ray bursts and the soft x-ray breakout of nearby type II supernovae.

We describe an imaging photon counting system for the EUV and its application to the measurement of the imaging quality of CDS EUV telescope for SOHO. The detector system uses an open window micro-channel plate intensifier coupled to a CCD with a fiber-optic taper. The digitized data are processed using a transputer based processing system which resolves the channel pores in the front micro-channel plate. The pores are used to register the EUV image. Dithering of the detector is used to enhance the resolution.

Free-standing transmission gratings will be used in a new generation of space instruments for magnetosphere energetic neutral atom (ENA) imaging which requires efficient suppression of the exceptionally strong background extreme ultraviolet (EUV) and UV radiation. The first results of the experimental study of grating (period 200 nm) optical properties in the 50 - 130 nm wavelength range are presented. It is shown that grating transmission strongly depends on polarization of the incident radiation which makes gratings efficient polarizers. Possibilities of using a single grating and crossed gratings for EUV filtering are discussed.

A comparison of various rigorous methods of analysis for soft x ray and XUV surface-relief gratings is presented. Example results for a wide range of groove width-to-groove-spacing ratios and angles of incidence are presented for lamellar gratings. Diffraction efficiencies for gold lamellar gratings obtained from the integral and the characteristic wave methods of analysis are compared with previously published numerical results. The accuracy, the convergence, and the stability of the numerical methods are discussed.

The optical performance achieved in many x-ray imaging applications is severely degraded by surface scattering effects. Residual surface roughness over a broad range of spatial frequencies must be specified and controlled for many applications of interest. Specifying the traditional surface `figure' and `finish' is inadequate for assuring the desired performance of high resolution imaging systems at these very short wavelengths. `Mid' spatial frequency surface errors that span the gap between the traditional `figure' and `finish' errors are often the dominant error source for both grazing incidence applications and those utilizing enhanced reflectance multilayers at normal incidence. Wide-angle scatter from surface microroughness severely reduces the reflectance of these multilayers whereas the small-angle scatter from the mid spatial frequency surface irregularities will degrade the resolution or image quality. A linear systems formulation of surface scattering theory results in a surface transfer function which characterizes the image degradation effects of residual surface irregularities over the entire range of relevant spatial frequencies. Image quality predictions obtained with this linear systems model agree favorably with experimental data for several different x-ray imaging systems. Parametric performance predictions can thus be used to determine realistic optical fabrication tolerances for x-ray astronomy, microscopy, and synchrotron source applications.

The Multi-Spectral Solar Telescope Array (MSSTA) is a rocket borne cluster of normal- incidence multilayer coated telescopes for the high-resolution study of the solar atmosphere and corona. In previous papers, we have described the design, calibration, and flight of the MSSTA, and reported qualitative results of those solar observations. In the present paper, we describe the MSSTA's measured quantitative instrument response to the optically thin solar coronal plasma, and present an example of the derivation of solar temperature and density diagnostic information from four photographic images obtained during the instrument's successful inaugural flight in 1991.

We present a concept study for a mission to provide wide field x-ray imaging spectroscopy. Many astrophysical studies in the x ray regime demand both high energy resolution (approximately 5 eV) as well as high angular resolution (approximately 10'). Examples of such studies are: clusters of galaxies, from those with sub-clumps to those at the edge of the universe (minimum radii approximately 15'); individual galaxies (nearby ones are easily resolvable on the 10' scale); deep sky surveys for clusters and QSO/AGN, which necessitate optimal sky coverage with the avoidance of source confusion for long exposures (approximately 2 multiplied by 10⁵ sec); supernova remnants (SNRs) in galaxies such as the LMC, SMC and Andromeda; knots in galactic SNRs such as Cas-A; and fine structure in the interstellar medium (ISM). Other studies that require a wide FOV and high energy resolution are studies of the large scale structure of the ISM, nearby clusters of galaxies, and large SNRs, such as the Cygnus loop and the Vela/Puppis region. The instrument concept we propose, the Wide Field X-ray Imaging Spectrometer (WFXIS), will combine the critical characteristics of wide-field, high-resolution x-ray imaging with high energy resolution, and thus provide unique capabilities not available on any single current or planned mission in which NASA is participating. Our preliminary design consists of ROSAT-sized zerodur mirrors with a Ritchey-Chretien figure; approximately 2.5 meter foal length; and a single focal plane detector made up of a 500 multiplied by 500 pixel array of either microcalorimeters or superconducting tunnel junctions. The energy range covered by this system will be approximately 0.1 - 2.5 keV. The main points of this work are: the science is outstanding; the technology for mirror production and design is in hand; and detector technology has reached the stage that it makes sense to begin planning for the ability to make 500 multiplied by 500 pixel arrays with a factor of 10 improvement in energy resolution over available CCDs.

The rocket and then the satellite investigations of the solar ionizing flux were started nearly fifty years ago (1946) but they still have not led to the permanent monitoring of the soft x ray and EUV solar radiations -- the principal factor that is controlling the main processes and parameters of the ionosphere and upper atmosphere and the energetics of solar-terrestrial relation. In view of this important fact and taking into account the EUV and particularly x ray variability which differs strongly for each of the solar rotations and solar cycles especially during solar flares, our knowledge of these fluxes is astonishingly incomplete. The main reason of the absence of the permanent solar radiation patrol is exclusively connected with technical and methodological difficulties of the space measurements in this spectral range. The present paper proposes a possible way of deciding the problem using the experience of the S.I. Vavilov State Optical Institute in the measurements of the solar ionizing fluxes on the satellites Cosmos-262 and Cosmos-381. The optical apparatus for the space permanent patrol are briefly described and some methodological problems of the information processing are discussed taking into account the real space conditions under which the registration of the EUV and x- ray fluxes is carried out.

The Advanced X-ray Astrophysics Facility (AXAF) is the x-ray component of NASA's Great Observatories. To be launched in late 1998, AXAF will provide unprecedented capabilities for high-resolution imaging, spectrometric imaging, and high-resolution dispersive spectroscopy, over the x-ray band from about 0.1 keV to 10 keV. With these capabilities, AXAF observations will address many of the outstanding questions in astronomy, astrophysics, and cosmology.

The alignment test system for the AXAF-I high-resolution mirror assembly (HRMA) performs a double-pass Hartmann test, in which a beam of light emitted from the focus of the HRMA is reflected back through the HRMA by an autocollimating flat (ACF). Measurements of the displacement of the beam on its return to the focal plane can be used to determine the misalignment of the HRMA, and also some information about errors in the shapes of the HRMA mirrors. Beam displacements caused by imperfections in the ACF can be distinguished from those caused by the HRMA by taking measurements with the ACF in different positions. This paper shows how to use such measurements to calibrate the system to compensate for errors caused by the ACF. Simulated results based on measured ACF surface data are presented.

The Advanced X-ray Astrophysics Facility (AXAF) mirrors represent the largest, most precise, grazing incidence optics every built. The eight cylindrical mirrors, 0.84 meters long, and ranging in diameter from 0.6 to 1.2 meters, have all been successfully fabricated. The optical surfaces were fabricated using a deterministic, computer controlled, approach. Modeling of the computer controlled process was employed to achieve desired figure levels in a minimum of polish/metrology cycles. Figure error corrections of 80 to over 90 percent per cycle were routinely achieved. Final full-bandwidth figure levels ranged from about 180 angstroms rms to about 40 angstroms rms. Surface roughness values range from about 3.5 to less than 2 angstroms, rms, over a bandwidth of 1 to 1000 mm^-1. Numerous metrology cross-checks give good confidence in the data. The fabrication, modeling, and metrology are described. Results of figure correction are presented. We also present an estimate for the predicted performance of the eight mirror ensemble and compare that with program requirements and goals.

The NASA Advanced X-ray Astrophysics Facility-Imaging (AXAF-I), one of NASA's Great Observatories, will be launched in 1998. The AXAF-I High Resolution Mirror Assembly (HRMA) will provide sub-arc second imaging resolution over the expected mission life of five years. During assembly and operational life of the telescope, small dimensional changes of the structural support system can degrade the telescopes resolving power by introducing unwanted forces. The forces that are introduced depend, in part, on the long term temporal dimensional stability of the materials that are used in the telescope. A year-long stability study carried out at the university of Arizona Dimensional Stability Laboratory recently concluded. Cyanate ester-based composites, 7050-T7451 aluminum, LR-35 invar, 6Al-4V titanium, 6061-T6 aluminum and Zerodur were studied. The Zerodur material was found to be stable to better than 0.03 ppm/yr. The titanium was found to be stable to better than 0.5 ppm/yr. The 7050- T7451 aluminum and cyanate ester-based composites were found relatively unstable but their instability improved significantly with time. Monte-Carlo and deterministic techniques were used to predict the effects of the instability on the telescopes' performance. Temporal instability effects were within the systems top level requirements.

The AXAF VETA-I mirror x-ray test results have been cross checked with predictions based upon the HDOS metrology measurements and calculations of the effects of imperfect test system geometry and mirror mount induced distortions. The cross check was done by comparing the VETA-I x-ray test results with a VETA-I model, which is a computer simulation of the VETA-I mirror performance during the x-ray test. The HDOS (Hughes Danbury Optical Systems, Inc., Danbury, Conn.) metrology measurements (with CIDS, PMS, and WYKO) were performed after the VETA-I x-ray test in order to determine the surface figure errors of the mirror pair, including the overall surface map and the surface roughness. Mirror performance was predicted based on the measured surface figure errors and x-ray scattering theory. All the VETA-I x-ray test data (FWHM, encircled energy, effective area, wing scan, and ring focus) were cross checked with the HDOS metrology measurements. The results of this study show reasonably good agreement between the x-ray test data and the metrology data. Similar analysis should be performed for the HRMA mirrors, which is an important step in securing a scientifically successful AXAF mission.

Electron-impact x-ray sources will be used to calibrate the Advanced X-Ray Astrophysics Facility (AXAF), and models of the source x-ray spectra are necessary in forecasting the calibration performance. We simulate the spectra of x-ray lines and continuum (0.1 - 13 keV) arising from electron impact on solid targets. We use simple models for electron transport, line and continuum emissivities, and radiative transport through the target. The electrons are attenuated in energy in the target but are unscattered in direction. The continuum x-ray emission is modeled as bremsstrahlung, and the characteristic x-ray line emission is modeled by electron collisional ionization followed by radiative decay to form the lines. X-ray attenuation is also included in the radiative transfer through the target. Multilayer or compound targets can be easily treated. We compare the spectra produced by this model to the model of Pella et al. and data from metal targets.

The High Resolution Mirror Assembly (HRMA) of the Advanced X-ray Astrophysics Facility (Imaging) (AXAF-I) consists of four nested paraboloids and four nested hyperboloids, all of meter-class size, and all of which are to be assembled and aligned in a special 15 meter tower at Eastman Kodak Company in Rochester, NY. The goals of the alignment are (1) to make the images of the four telescopes coincident; (2) to remove coma from each individually; and (3) to control and determine the final position of the composite focus. This will be accomplished by the HRMA Alignment Test System (HATS), which is essentially a scanning Hartmann test system. The scanning laser source and the focal plane of the HATS are part of the Centroid Detector Assembly (CDA), which also includes processing electronics and software. In this paper we discuss the design and the measured performance of the CDA.

We report on the development and evaluation of a redesigned version of the Penning gas discharge source of x-ray and EUV radiation previously described by Finley et al. The most significant new features are the use of stronger permanent magnets and spill-proof quick- disconnect water cooling line fittings. Using aluminum cathodes and Ar discharge gas, and with a 0.5 mm by 5 mm exit aperture on the source, we obtained an absolute flux in the bright Al IV line at 129.73 A of order 5 multiplied by 10¹¹ s^-1 sr^-1, and of order 5 multiplied by 10⁹ s^-1 sr^-1 for the Ar I line at 56 A. Detailed spectral analysis of the lines near 56 A is reported. The application of this source to the prelaunch calibration of the AXAF x-ray astronomy observatory is discussed, with emphasis on use of the narrow line at 56 A for calibrating the spectral resolution of the AXAF transmission grating spectrometers.

In preparation for calibrating the Advanced X-ray Astrophysics Facility, a multicomponent x- ray source system has been assembled for use at the x-ray calibration facility at MSFC. The system consists of an electron impact point source with filters, a penning gas discharge source, and two monochromators fed by rotating anode x-ray generator. The purpose and predicted performance characteristics of these elements are described as they apply to the AXAF calibration. The planned source characterizations, performed in June 1995 through June 1996 time period, are also described.

The Multi-Spectral Solar Telescope Array II (MSSTA II), a rocket-borne solar observatory, was successfully flown on November 3, 1994 obtaining solar images in multiple XUV and FUV bands with an array of compact multilayer telescopes. Extensive measurements have recently been carried out on some of the multilayer telescopes at the Stanford Synchrotron Radiation Laboratory. These measurements are the first high spectral resolution calibrations of newly introduced MSSTA II instruments and instruments with lambda₀ less than 130 angstrom. Previous measurements and/or calculations of telescope throughputs have been confirmed with greater accuracy. Results are presented on Mo/Si multilayer bandpasses, and multilayer bandpass changes with time.

The AXAF-I High Resolution Mirror Assembly (HRMA) consists of four nested mirror pairs of Wolter Type-I grazing incidence optics. The HRMA assembly and alignment will take place in a vibration-isolated, cleanliness class 100, 18 meter high tower at an Eastman Kodak Company facility in Rochester, NY. Each mirror pair must be aligned such that its image is coma-free, and the four pairs must be aligned such that their images are coincident. In addition, both the HRMA optical axis and focal point must be precisely known with respect to physical references on the HRMA. The alignment of the HRMA mirrors is measured by the HRMA Alignment Test System (HATS), which is an integral part of the tower facility. The HATS is configured as a double-pass, autocollimating Hartmann test where each mirror aperture is scanned to determine the state of alignment. This paper describes the design and operation of the HATS.

The European Synchrotron Radiation Facility in Grenoble, France is the first one of the third- generation high-energy storage ring sources in the world and has been in operation for three years. It provides x-ray beams of unprecedented quality in an energy range from hundred eV to several hundred keV. In order to fully exploit the source quality adequate x-ray beamline optics are needed that can cope with not only the very low emittance but also the extremely high brilliance involving severe heat load. The strategies and the solutions of x-ray optics research and development at the ESRF that started seven years ago are described. The results of first experience gathered during more than two years of beamline operation on the performances of mirrors, single crystal monochromators, and multilayer structures exposed to these very powerful x-ray beams are presented, together with their mechanical supports for bending, cooling, and alignment. New developments like Bragg-Fresnel optics for microfocusing, x-ray phase plates for polarization studies, adaptive optics, cryogenic cooling, diamond crystals, and other relevant optics materials are included, too. It is shown that today the x-ray optics developed for the ESRF are capable of preserving the high quality of the x-ray beams, a result that was not clear at all a few years ago.

The on- and off-axis imaging properties of the first of two SODART flight telescopes have been studied using the expanded beam x-ray facility at the Daresbury synchrotron. From on- axis measurements the encircled power distribution and the point spread function at three energies 6.627 keV, 8.837 keV, and 11.046 keV have been measured using a one dimensional position sensitive detector. The data have been used to calculate the half power diameter (HPD) for three different SODART focal plane detectors, the high energy proportional counter (HEPC), the low energy proportional counter (LEPC) and the 19 element solid state array detector (SIXA). We found that the HPD decreases with increasing energy due to poorer figure error of the outermost mirrors. The HPD falls in the range from 2.3 to 3 arcmin for all detectors. Residual misalignment of the individual quadrants of the telescope was found to contribute to the HPD by approximately 10%. If 33% of the geometric telescope area near the edges of the quadrants are covered a reduction of 10% of the HPD can be obtained. On- and off-axis images generated from the one dimensional intensity distribution are presented. Finally the data have been used to calculate the variation of the effective area versus the off- axis angle.

Crystallographic and dispersion characteristics of muscovite at different reflection orders (2 divided by 24) for (001) lattice planes were investigated theoretically. Measurements of integral reflectivity were done for (10 divided by 38) reflection orders by using Cu and Mo X- tube radiation. Experimental results were compared with calculations for perfect and mosaic crystals. The integrated reflectivity for spherically bent mica crystals with R equals 100 and 186 mm have been calculated for various reflection orders. The results of these calculations show that muscovite crystals can be used in high reflection orders for high-resolution spectroscopy only if the crystal perfection is high enough, which provides the narrow reflection curve widths. These theoretical considerations are supported by results obtained in various plasma spectroscopic experiments. Nearly perfect muscovite crystals have been shown by using Lang and section topographic techniques for both flat and spherically bent muscovite crystals respectively. The high-quality of such crystals was also demonstrated using the scheme of obtaining a `parallel' x-ray beam and x-ray microscope schemes. Possible applications of high-quality muscovite spherical crystals are discussed.

X-ray optics typically rely on total external reflection and for hard x rays, the critical angle in any material becomes very small. This in turn leads to vanishingly small projected areas. To extend useful reflectivity to higher energies, the concept of multilayer coated reflectors has been proposed. Such hard x-ray multilayer structures require the capability to deposit ultra- thin (of the order of ten angstrom), ultra-smooth (of the order of a few angstroms rms), uniform, alternating films of high Z and low Z materials, with sharp interfaces and no interdiffusion between the layers. Standard vapor phase deposition processes such as evaporation and sputtering cannot achieve all the above goals. We have developed a new deposition process which does not involve the use of vacuum, is performed at a relatively low temperature, can be scaled up to large surface areas and to curved substrates, is low cost, and results in ultra thin, ultra smooth, uniform, high density films with sharp interfaces. This is optimal for the construction of multilayer x-ray optical components. This process is also capable of depositing films of high melting point noble metals such as iridium and osmium which cannot be deposited by evaporative procedures. The surface characterization and x-ray reflectivity of the films are presented.

The results of experimental and theoretical studies on passage of synchrotron radiation through capillary lenses of new generation are presented. The transmission coefficients for these systems in the range 8 - 10 angstrom are measured. An explanation of structure absence for focal spot is given.

The effect of x rays focusing by polycapillary arrays is investigated both theoretically and experimentally. Radiation concentration is a result of 1 - 2 reflection in straight polycapillaries. The focusing picture depends greatly on the form of channels cross-section (circular, hexagonal, or square). Conditions for maximum energy concentration are discussed. Results of numerous experiments on polycapillaries with circular and hexagonal channels are presented.

A quasiparallel beam after the first lens was focused by the second one. It is shown that the focus spots have rather high x ray intensity and their dimensions are dependent on the lenses geometry. The possibility of using such a scheme for analytical instruments is discussed.

The Multi-Spectral Solar Telescope Array (MSSTA) is a sounding rocket borne observatory designed to image the sun at many spectral lines in soft x-ray, EUV, and FUV wavelengths. Of the nineteen telescopes flown on November 3, 1994 the two Cassegrain telescopes and three of the six Ritchey-Cretien telescopes were focussed at NASA/Marshall Space Flight Center (MSFC) with a Zygo double-pass interferometer to determine the best positions of back focus. The remaining three Ritchey-Cretien and eleven Herschellian telescopes were focussed in situ at White Sands Missile Range by magnifying the telescopic image through a Gaertner traveling microscope and recording the position of best focus. From the data obtained at visible wavelengths, it is not unreasonable to expect that many of our telescopes did attain the sub-arc second resolution for which they were designed.

The design , construction and imaging experiments of a soft X-ray microscope which consists of acompact laser-produced plasma source (LPPS) , as well as a multilayer coated spherical condenser, and Schwarzschild optics are presented. The Schwarzschild optics was designed for numerical aperture of 0. 1 and magnification of 10. For the working wavelength of 18 nm calculations show that the resolution is expected to be 0.2im. We designed a 41 layer Mo/Si multilayer coatings of throughput centered at l8nm, and these coatings were deposited by magnetron sputtering. We put a Al/C multilayer filter in front of the image to block thelong wavelength radiation. The object on the primary experiments is a piece of Cu mesh of 55 pair lines/mm witha opening of 5m and bar width of 3im. The backlit mesh image were taken on Kodak X-ray film. The first lot of experiment data show that a spatial resolution better than 1im was obtained. Key words : Schwarzschild Optics , Soft X-Ray Microscope , Multilayer mirrors.

Polished silicon crystals, lacquered aluminum foil, and float glass substrates with respect to surface roughness. Co/C multilayers were then deposited by electron-beam evaporation with in situ monitoring x-ray signal and ion polishing (Kr⁺) for the metal layer. The specular as well as the transverse scan have demonstrated different qualities, influenced by the different substrates. The investigations were performed with both hard x-ray (8.05 keV) as well as soft x-ray (0.25 keV). The reflectivity varies up to factor 3 between the best and the worst of these substrates. The results of these investigations and a comparison between the coating performances are discussed.

We describe a concept for a NASA mission to study gamma-ray bursts, pulsars, and hard x- ray transients. That a large area all sky monitor is an outstanding design was demonstrated by the BATSE (Burst And Transient Source Experiment) on board the Compton Gamma-Ray Observatory (CGRO). The proposed All Sky Low Energy Gamma-Ray Observatory (ALLEGRO) will combine the best characteristics of BATSE and OSSE (Oriented Scintillation Spectrometer Experiment), namely continuous all-sky coverage with a reduced background obtained from relatively narrow field of view collimation. The design goals call for an effective area of greater than or approximately equal to 2000 cm² (in the 20- 200 keV range) provided by 35 separate detectors aligned to cover the entire sky, plus 1/8 ms time tagging of all events and energy coverage from 7 - 200 keV. We combine this with what have probably been the greatest advances in technology over the past few years, namely, advances in electronics, computing power, and data storage and retrieval. With these capabilities plus enhancements to the design based on our experience with BATSE and OSSE, we will explore the realm of high time resolution phase space with all-sky coverage at unprecedented sensitivity. Such a satellite will provide a myriad of fascinating studies of the hard x-ray sky. Three general areas where we expect to make major advances are the understanding of gamma-ray bursts, rotationally powered neutron stars, and binary x-ray sources. As an added bonus, this satellite will allow us to monitor the hard x-ray sky, provide hard x-ray maps, and even provide a stringent test of the general relativistic Shapiro delay.

Ion-beam-deposited boron carbide thin films have been produced and evaluated as normal- incidence, reflective coatings in the extreme ultraviolet. Reflectances of over 28% were obtained for wavelengths longer than 58 nm and as high as 38.6% at 92 nm, for a freshly deposited coating. Optical constants of sputtered boron carbide were calculated from experimental observations using the reflectance-versus-angle method. X-ray photoelectron spectroscopy analysis of the deposited film was performed in order to investigate its chemical composition and effects on the long-term stability of the coating's reflectivity.

The redesigned payload of the Multi-Spectral Solar Telescope Array (MSSTA), the MSSTA II, was successfully flown on November 3, 1994. The multilayer mirrors used in the normal incidence optical systems of the MSSTA II are efficient reflectors for soft x-ray/extreme ultraviolet (EUV) radiation at wavelengths that satisfy the Bragg condition, thus allowing a narrow band of the soft x-ray/EUV spectrum to be isolated. When applied to solar observations the temperature response of an optical system is quite sensitive to telescope bandpass because of the high density of lines in the coronal spectrum. We have designed a set of thin foil filters in conjunction with our multilayer optics to eliminate contaminant lines and specular reflectivity, thus enhancing the temperature diagnostic capabilities of our instruments. Extensive measurements have recently been carried out on the thin foil filters at the Stanford Synchrotron Radiation Laboratory. We describe here the design and performance of thin foil filters developed for the MSSTA II.

Bragg reflection from a logarithmic spiral dispersive element (LSDE) has been considered. LSDE is known to have a wide angle of reflection for an x-ray source placed in a spiral focus. Although this is true for a 2-dimensional spiral, it is not the case in 3 dimensions. For a 3- dimensional LSDE only narrow strip on the spiral surface contributes in reflection of radiation from a point source placed in the spiral focus. This imposes certain limitations on a spiral design and on detector dimensions.

A planar diode, rf-sputtering system, modified to triode operation by addition of a ring filament surrounding the anode, is described. Alternately timed sputtering is used to fabricate multilayer films with good characteristics, predominantly in the extreme ultraviolet (EUV) range of 15 to 20 nm. Fabrication of stable films of niobium/silicon is discussed, along with characterization results that utilized x-ray diffraction (XRD) and synchrotron source reflectance measurements. Characteristics of an optic that was designed and used to photograph the sun at 18.0 nm from a rocket-borne experiment are described.

The long trace profiler (LTP) has been used to assure the quality of x-ray beamline mirrors with fixed radii of curvature after they have arrived from the manufacturer and before they are permanently set in the beamline. In the case of some adjustable radius mirrors, the adjustment mechanism may require setting outside of the beamline. The bending mechanism often bends the mirror into a tangential cylinder, which is difficult to measure by interferometric methods. Measuring medium- to long-radius cylinders is a routine task for the LTP. Thus, a bendable (adjustable radius) mirror may be adjusted in the metrology laboratory before the mirror is placed in the beamline. This paper describes the method of adjustment and surface quality assessment for bendable, adjustable radius mirrors in general, and shows results for a small mirror that is bent into an elliptical cylinder.