The focusing properties of zone plates have a long history spanning over a century. The fabrication technology has continually improved and has made significant advances in the last decade so that zone plates now can be fabricated with the smallest zone widths of several tens of manometers and near diffraction limited performance. For applications such as x-ray microscopy, these high resolution zone plates allow the possibility of observing biological samples in a natural, i.e. wet, environment with resolution an order of magnitude better than optical microscopy. In addition to microscopy, zone plates are critical to many x-ray applications where the focusing, imaging, and dispersive properties can be put to use. The key challenges for making better zone plates are to improve the efficiency and resolution while maintaining comfortable working distances and extend the wavelength range available. In order to meet these challenges, refinements in zone plate fabrication technology, better line placement distortion measurement/control techniques, and new processing ideas are under development.

Sputtered-sliced transmissive x-ray zone plates consisting of concentric rings of Al and Cu have been fabricated and tested using the 8.04 keV k-a line from Cu. Due to the need for high aspect ratios for this 1.54 A radiation, magnetron sputtering onto a rotating opaque central wire was chosen as the fabrication method. Both the fabrication technology and initial results are presented.

We describe the design and performance of multiple-layer, selective-reflection, selective-suppression coatings for the 900 - 1200 Å band. These coatings are designed to optimize both high reflectivity at a desirable wavelength and low reflectivity at an undesirable wavelength. The minimum structure for a selective coating consists of a thin metal or metal oxide layer (50 - 150 Å thickness) over an aluminum substrate protected with a semi-transparent dielectric (100 - 1000 Å. thickness). Predicted coating performance is strongly effected by varying the layer combination and thickness. Selec-tivity may be enhanced or augmented with further dielectric / metal layers. A graphical method of optimizing the coat-ing layer structure is developed. Aluminum, silicon, their oxides, and gold have been investigated as coating layer materials. We have fabricated a very simple coating with a 1026 to 1216 Å reflectivity ratio. greater than 100. Such reflection / suppression coatings may be of great utility to spaceborne EUV spectrographs. Strong background geocoronal emission lines could be rejected by use of properly coated collecting optics. By eliminating a diffraction element to reject background lines, efficiency losses and scattering may be avoided.

The X-ray-optical performance of sputtered polycrystalline films in grazing incidence geometry is influenced by their surface roughness and the presence of oxide layers. The surface roughness of the films has been characterized by transmission electron microscopical ( TEM) techniques. A relation between the measured X- ray reflectivity and the microtopographic features seen in the TEM has been found. Rockingcurves of Ta- and Fe-films are influenced by oxide layers. Thin oxide layers produce an additional amplitude modulation in the reflectivity, from which the density and the thickness of the oxide layers can be derived with high accuracy.

Much work has been done to characterize materials which can be used for filters in the vacuum ultraviolet and X-ray region of the electromagnetic spectrum from about 1500A down to 10Å more or less. This paper compiles and compares the results of different measurement programs, including very recent work which better quantifies transmission as a function of wavelength for various filter and window materials. Of particular interest is some correlated data on Lexan with empirically derived linear absorption coefficients as a function of wavelength and some recent data on the effect of aging on aluminum filters. Also included are some test data and comments on recent efforts to use composite materials to design or adjust the bandpass of a filter to meet particular research requirements. In addition, there are some comments on the development of thin film materials for other uses such as in photocathodes and laser targets. As a result of the combined work reported here, data is made available which will make it easier to specify and predict the performance of filters and windows for specific applications.

Large area multilayer beamsplitters (1 cm² ) were produced for use at oblique incidence in the soft X-ray range. Mo/C multilayer reflectors were deposited on top of a self supporting silicon carbide carrier film. The role of the supporting film and the stress induced by the multilayer are addressed. Progress towards optimization of the flatness and transmission enhancement of the beamsplitters (thinning of the carrier layer and adjusting its stress through etching ) is presented. Experimental reflectivity and transmission results at 13.3 Å are compared with theory.

Methods of designing strong, high transmission soft x-ray windows are discussed. A material which contains several elements, most notably 0, N, and C, produce the most spectrally neutral window. It is noted that a predominantly single element material such as diamond is in reality an edge filter. A structure to support very thin films and to provide exceptional mechanical strength is discussed. Pressure cycling data for such a supported window are presented.

Soft x-ray telescopes require filters that block visible and infrared light and have good soft x-ray transmission. The optical properties of possible materials are discussed and the fabrication and testing methods for the filters used in a 10 inch normal incidence telescope for λ = 63Å are described. The best performances in the λ = 44 114Å wavelengths range is obtained with foils of carbon and rhodium.

The X-ray spectrometer (XRS), which is being developed for one of the focal plane instruments of the Advanced X-ray Astrophysics Facility (AXAF), requires filters with high X-ray transmittance, high background rejection, and operation at cryogenic temperatures. Thin foil filters can provide high X-ray transmittance and the required rejection for low energy radiation. The results of the test program demonstrate that these filters are fully successful at cryogenic temperatures and therefore can provide blocking filters for the XRS with the required performance.

Beamsplitters find a direct application in plasma diagnostics by making possible multiple observations at different energies through one single observation window. Proof of evidence was made with a new optical element ( "bichromator" ) consisting of a Mo/C multilayer beamsplitter produced by microfabrication technology and a W/C multilayer mirror. The chronometric shift between two neon emission lines from a Z-pinch plasma source was measured in the keV range. The advantages of the device will be highlighted.

The fabrication of the Technology Mirror Assembly (TMA) is complete, and performance predictions were made based upon mechanical and visible light measurements of the surface properties. An X-ray calibration program has been executed, and a preliminary analysis of a portion of the data is presented. The X-ray image distribution results are in reasonable agreement with the performance predictions which were calculated prior the start of the X-ray tests. The measured X-ray imaging performance approaches that expected for the Advanced X-ray Astrophysics Facility (AXAF).

X-ray contact microradiography using a laser-produced plasma pulsed x-ray source provides several advantages for imaging dynamic biological systems. We have applied such an x-ray system in the study of silica deposition in living leaf blades of Zia and the developmental morphology of maize inflorescence. Such a study provides a means for the selection of high silica varieties in crop plants, which has been correlated with high resistance to insects and fungi. Real-time x-ray imaging may be obtained using a shadow projection method. For this purpose, a shadow projection microscope was constructed by modifying a scanning electron microscope for real-time imaging. Preliminary results in the study of floral development in maize will be presented. In addition, implementation of this real-time imaging system to the laser plasma x-ray system will be discussed.

Normal incidence multilayer x-ray mirror technology has now advanced to the point that high resolution x-ray microscopes with relatively large fields of view are feasible. High resolution aplanatic imaging x-ray microscopes configured from low x-ray scatter normal incidence multilayer optics should be ideal for laser fusion research, biological investigations, and for astronomical studies when used in conjunction with grazing incidence or multilayer x-ray telescope systems. We have designed several Schwarzschild x-ray microscope optics. Diffraction analysis indicates better than 400 A spatial res-olution in the object plane up to a 1 mm field of view can be achieved with 125 A radiation . We are currently fabricating a 20x normal incidence multilayer x-ray microscope of 1.35 meter overall length. We have also analyzed and designed other microscope systems for use in conjunction with x-ray telescopes. We report on the results of these studies and the x-ray microscope fabrication effort.

We have designed and built a cylindrical grazing incidence monochromator (mirror) for 1.54Å CuKa x-rays. W/C multilayers were deposited onto thin sheets of mica and then bent into cylindrical shapes. The favorable properties of mica, including monolayer smoothness and malleability when used in very thin sheets, provide an ideal substrate material. X-Ray diffraction measurements indicate a multilayer d spacing of 1.07 nm. Such a small d spacing multilayer can be used in cylindrical optics with focal lengths of 50 cm or less. Experimental results using the cylindrical multilayer optic are compared to code predictions.

The development of multilayer optics has profound implications for soft x-ray/EUV (XUV) astronomy. During the October 1987 flight of the Stanford/MSFC Rocket X-Ray Spectroheliograph, narrow wavelength band low scatter soft x-ray/EUV spectroheliograms were obtained with 1 arc second spatial resolution at λ~ 173 A (Fe IX, Fe X) and at X, 256 A (He II). Although the Cassegrain telescopes used in this experiment were small (63.5 mm diameter) and utilized spherical rather than paraboloidal/hyperboloidal mirrors, the images produced exceed in quality any XUV spectroheliograms previously obtained with either normal or grazing incidence techniques. We describe a new rocket spectroheliograph instrument, the Multi-Spectral Solar Telescope Array (MSSTA), that is currently being prepared for launch in September 1989. This instrument will utilize true Ritchey-Chretien optics of 127 mm diameter and parabolic Herschelian optics of 40 mm diameter, which will allow spectroheliograms to be obtained over the soft x-ray/EUV/VUV spectral range (40 Å - 1550 Å). The performance of this new instrument should definitely demonstrate the unique combination of ultra-high spatial resolution and spectral differentiation which multilayer optics afford for astronomical observations. The MSSTA will also represent the first astronomical use of an important new optical device, the multilayer grating. The MSSTA should obtain unprecedented information regarding the structure and dynamics of the solar atmosphere in the temperature range 104 K to 107 K.

The finite element method is used in the thermal and structural analyses of a 3-channel silicon-crystal monochromator in a wiggler x-ray beam. Liquid gallium and water are used as coolants. Liquid gallium is fed into the monochromator by an induction pump designed and built for this purpose at Argonne National Laboratory. The choice of gallium as a coolant is based on its high thermal conductivity, very low vapor pressure (appropriate in high vacuum environments), nontoxicity, and stability. For contrast, a parallel analysis for the monochromator cooled with water is also presented. The results of this analysis are compared with the experimental data taken at the Cornell High Energy Synchrotron Source (CHESS) using a 6-pole wiggler as the radiation source.

The Solar-A soft X-Ray telescope is one of several instruments which will be launched aboard the Japanese Solar-A Satellite in 1991, to study the sun during the next period of sunspot activity. Severe launch and on-orbit thermal conditions and the need to provide high resolution over a half minute field of view place unusually stringent requirements upon the mechanical and optical design of this grazing incidence solar x-ray telescope. The instrument must survive an axial acceleration of 18-g, and a lateral acceleration of 7-g over a large vibrational frequency spectrum. A 2.43 arc-sec image quality is specified on-orbit from -2.5 °C to 22.5 °C. In addition, the mount must provide negligible distortion during x-ray testing at 1-g with its optical axis horizontal. This paper describes the process of designing the mirror and mount configuration to successfully meet these demands. As a result of this effort, three unique features were developed which extend the state-of-art in the design of gazing incidence systems. First, by using two hyperbolic surfaces (as suggested by Nariai) instead of the parabola-hyperbola design of a conventional Wolter type I design, a flatter focal plane with better imaging at the edge of the field was obtained. Second, special software was used to link the structural/thermal finite element analysis programs to the optical performance prediction programs. This resulted in a significantly more rapid optimization of both the mechanical design for the critical mounting assembly, and in establishing error budget allocations. Third, the telescope was designed with both hyperbolic optical surfaces in tandem on one substrate, in order to survive launch and guarantee maintenance of alignment between the two surfaces. These design features were successfully demonstrated on the flight model and were fully qualified on the mass model during vibration tests.

Metal multilayer mirrors have been designed for the ALEXIS satellite, which is to carry six wide field telescopes to perform an all-sky survey in three or four narrow wavelength bands in the EUV. Comprised of alternating layers of molybdenum and silicon, the mirrors are optimized to provide maximum reflectivity at angles from 11.5 to 17° off normal incidence and at wavelengths of 133, 171, or 186Å. Simultaneously, the mirrors use a "wavetrap" described below to suppress reflectivity at 304Å, where the extremely strong geocoronal line of He II causes severe background problems. Low reflectivity at 304Å is achieved by superposing two layer pairs that provide destructive interference with an effective 2d spacing of 152Å. The Mo layers in this wavetrap must be very thin, about 10Å each, in order to allow the shorter wavelengths desired for peak reflectivity to penetrate without significant attenuation. Because refraction changes the effective angle of passage through the wavetrap, a joint optimization between layer thicknesses in the deep layers and the wavetrap layers must be performed for each target peak wavelength. For the 186Å mirror, the optimum design from substrate upward is 40 layer pairs, each 74Å Si and 31Å Mo, followed by 2 layer pairs, each 55Å Si and 10Å Mo. Calculations predict this design will have a peak reflectivity at 186Å of 35 percent and a 304Å reflectivity less than le, if available optical constants are correct and the multilayer can be fabricated without difficulty. We will present details of the calculations and laboratory measurements of the reflectivity performance attained with prototype mirrors.

A tunable double crystal x-ray monochromator using matched pairs of multilayer-coated mirrors has been designed and constructed at the CfA. Each set of mirrors is usable over a factor of three range of wavelengths and by changing the mirrors the mechanism can be used at wavelengths of ~10 to >300 Å (40ev to 1.2kev). The mechanism maintains a fixed entrance and exit beam and is controlled by a single stepping motor; a simple mechanical linkage provides the additional motions which arc necessary to move the mirrors to the required positions. The novel features of this design are the simplicity of the mechanism and the use of narrow-band multilayer mirrors in place of crystal elements. Details of the design are presented as well as results of preliminary throughput and resolution tests using a pair of multilayer mirrors made to be particularly narrow band in order to be used in this type of instrument.

A spherical grating monochromator (SGM) has been designed and installed in beamline 48913 at Beijing Electron Positron Collider (BEPC) for synchrotron radiation soft x-ray photoemission experiments. There are four laminar gratings in this monochromator to covering the region of 10 -1100ev. On three of them, which covering the soft x-ray range, a supersmooth blank surface with large radial (57M) and high figuring accuracy (>λ/50) is required to suit the monochromator high resolving power desgn (>2000) and reduce the beam power loss. In this paper, the methods of fabrication and metrology has been described, the test results of this plank using WYKO and ZYGO show that the surface roughness of this blank is about 2Å RMS with 0.014 figure tolerance.

In multilayer assemblies consisting of alternating high and low absorption index materials the strongly absorbing (metal) component layer is usually microcrystalline. The crystallite size influences the soft X-ray reflectivity of the stack by determining the effective reflecting area of the stack and the diffuse scattering contribution. The influence of the deposition parameters on the structure of ion-beam sputtered Ni and a-C films is described together with the associated multilayer soft X-ray reflectivity spectra as a function of sputtering energy, d-spacing and film thickness ratio.

We report on the design and the theoretical ray trace analysis of the optical systems which will comprise the primary imaging components for the Stanford/MSFC Multi-Spectral Solar Telescope Array (MSSTA). This instrument is being developed for ultra-high resolution investigations of the Sun from a sounding rocket. We have analyzed doubly reflecting systems of sphere-sphere, ellipsoid-sphere (Dail-Kirkham), paraboloid-hyperboloid (Cassegrain), and hyperboloid-hyperboloid (Ritchey-Chretien) configurations. For these mirror systems, we have performed ray trace analysis and generated through-focus spot diagrams, point spread function plots, and geometrical and diffraction MTFs. The results of these studies will be presented along with the parameters of the Ritchey-Chretien optical system selected for the MSSTA flight. The payload, which incorporates seven of these Ritchey-Chretien systems, is now being prepared for launch in late September 1989.

The enhanced reflectance achieved by recent developments in X-ray optics multilayer technology have made normal incidence X-ray/EUV telescopes feasible for many applications of interest. Conventional optical designs with obvious advantages over the somewhat cumbersome grazing incidence designs of Kirkpatrick, Baez, and Wolter can thus be utilized even at X-ray wavelengths. Preliminary results of actual flight data from such systems suggests great promise of scientific achievement from this new technology. It is widely recognized that "supersmooth" substrates are required since microroughness can seriously reduce the reflectance obtained from the multilayer. The (spectral) reflectance has thus become the most common measure of performance in the evaluation of X-ray multilayers. This ability to collect radiation and direct it toward a focal plane is a necessary but not sufficient condition for producing high quality images. The second and equally important condition is the ability to concentrate that radiation in a very small region in the focal plane. It is this condition that allows high spatial resolution images to be obtained. Conventional optical figure requirements are tolerable since these systems are usually far from diffraction-limited at their operational wavelengths. Optical substrates with satisfactory "figure" and "finish" for X-ray/EUV applications have been successfully demonstrated. However, image quality degradation due to "mid spatial frequency" optical fabrication errors which bridge the gap between figure and finish is not nearly so well understood. It is the small angle scatter produced from these mid spatial frequency optical fabrication errors that will limit the practical resolution attainable from this promising new technology. Parametric optical performance predictions illustrating the capabilities and limitations of X-ray multilayers will be presented. The results of these calculations indicate that sub arc second resolution is indeed possible provided sufficiently smooth layer interfaces are maintained; however, image degradation occurs in a rather non-intuitive manner with varying interface PSD slope.

It is well known that the presence of optical fabrication errors on the optical surfaces of an imaging system will degrade image quality. Theoretical treatments of these effects covering any wavelength domain can be found in the literature, and include the conventional grazing incidence X-ray/EUV optical systems. However, very little work has been done toward extending image quality analysis into the new and promising field of normal-incidence X-ray/EUV multilayer optical imaging systems. In this paper, a detailed physical optics (interference and diffraction) treatment of surface scatter phenomena due to optical fabrication errors in X-ray/EUV multilayers over the entire relevant range of spatial frequencies will be described. The effects on the scattered radiation field of a variety of assumptions concerning the statistical correlation of interface roughness will be explored. It is well known that, at soft X-ray wavelengths, substrate figure errors blur the image. In this paper, it will be shown that uncorrelated interface microroughness reduces the reflectance of multilayers in addition to causing wide angle scatter, and that small-angle scatter from mid spatial frequency optical fabrication errors limits the achievable image quality (fractional encircled energy.)

Laser Raman spectroscopy has been found to he useful for characterizing amorphous semi-conductor niultilayers especially the interfaces of multilayers. We have extended this technique to the characterization of W/C niultilayers used in soft x-ray optics and ultrathin sputtered carbon films. Unlike the multilayers previously studied which contained only semiconductors and di-electrics, these are semiconductor/metal multilayers. The dominate Raman feature is due to a-C and consists of a broad peak at about 1580 cm-1 (G-peak) and a shoulder at about 1400 cm ^-1 (D-peak). This was deconvoluted with Gaussians to yield two peaks (one at 1570 cm' and the other at 1420 cim 1). Among the multilayer samples peak positions and relative magnitudes changed little. The intensity ratio of the D-peak to G-peak was much larger for multilayer sample, however , than for the single layer pair samples. This may due to different. forms (amorphous or crystalline) of tungsten layer in the samples and indicate the differences in the structure of carbon layers and tor bonding structure at interfaces.

Multilayer coatings have been designed for peak reflectivity at 182.2Å and 45° angle of incidence. An optimizing computer code was used to find the best layer thicknesses and total number of layers in the structure. Silicon was chosen as the spacer material and molybdenum for the absorber. Mirrors were produced both by sputtering and by electron-beam evaporation in ultra-high vacuum (UHV). The mirrors fabricated by sputtering were made from high-purity source materials by moving a substrate table over the sources. The UHV evaporated samples were produced in a silicon/metals MBE system with a base pressure of 5X10-11 torr. The layers were formed by alternately opening shutters over the two electron-beam evaporators. The deposition rates were feedback stabilized and the shutter timing was computer controlled. The substrate was rotated to produce uniform layers and heated to 200°C for one sample. Rutherford Backscattering Spectroscopy (RBS), x-ray diffraction (XRD), and scanning tunneling. microscopy (STM) were used for characterization. Synchrotron radiation from SURF-II was used to measure the reflectivity as a function of wavelength in the design region. All of the mirrors have amorphous Si layers and polycrystalline Mo layers. The measured reflectivity at 45°, scaled for 10096 S-polarized light, ranges from 29% for a sputter-deposited mirror to 47% for the mirror produced in the MBE system at a substrate temperature of 200°C.

An imaging-based experimental technique is proposed for measuring the spatial distribution of the absolute soft x-ray characterization of a flat multilayered x-ray optic. The six components in this calibration technique are these: (1) a nearly monochromatic, point-like soft x-ray source, sufficiently bright; (2) the flat multilayered x-ray optic under test; (3) some position-sensitive soft x-ray photon-counting detector assembly; (4) vacuum chamber with theta-two theta drive, goniometers, stepper motors, etc; (5) a micro/mini computer with image-processing/frame-grabber board; (6) a bookeeping algorithm implemented in software to process the images being accumulated and to successively step the vacuum chamber to the next theta-two theta detent. At the Lawrence Livermore National Laboratory, position-sensitive detectors are the subject of experimental and theoretical studies for their suitability in novel, imaging-based technique anticipated to have substantially higher daily throughput ( wafers/day ) than is possible from the prevailing non-imaging facilities. A recent design, and the computaional model behind it, will be presented.

The measured XUV reflectance versus incidence angle is presented for several multilayer reflectors having various periods, fabricated from W/C, Mo/Si, and Cr₃ C₂ /C. These measurements are compared with calculations using recently derived optical constants, which are also presented. We find that the agreement between the measured and calculated reflectance is best for non-zero values of the interface roughness parameter.

Metal oxide multilayers provide reflecting coatings in the 15-50 nm range with exceptionnal properties. We discuss filters featuring narrow band-passes and/or very sharp cut-offs. Possible effects of degraded manufacturing processes are also evaluated.

Precision non-contact flow polishing of exotic optical materials(i.e. Beryllium, Zerrodur,Sapphire, & Electroless nickel) will be discussed. Roughness measurements of surfaces and interferometric results will be shown.Examples of Aspheric contours polished to 1 Angstrom RMS are presented with discussion of the flow polish technique applied to finishing of optical systems.

The performance of multilayer x-ray mirrors is improved by smoothing the boundaries within the multilayer stack with ion bombardment at grazing angles of incidence. The process is applied to Co-C and to RhRu-C mirrors for normal incidence telescopes at λ = 64 and λ = 114Å and the reflectivity is increased by a factor of two in both cases. Accumulation of roughness during deposition is eliminated.

Holographic lithography was used to produce a 0.36 μm spatial period grating on top of a Mo/C layered synthetic microstructure. The pattern was transferred to the multilayer mirror by reactive ion etching. The performance of the device has been evaluated at the Cu.Lα,β3 wavelength ( 1.33 nm ). A simple theoretical model explains the main features of the diffraction efficiency of the soft X-ray highly dispersive multilayer mirror.

EUV telescopes are typically Wolter Type telescopes. Made with glancing incidence mirrors. Recent developments in miltilayer caotings have opened up the possiblitity of using normal incidence mirrors in a Cassegrain configuration for EUV telescopes. Each of these approaches has advantages and disadvantages. Glancing incidence mirrors have a higher reflectivity with a braod bandwidth, but the sufaces are dificult to make. Normal incidence mirrors are easier to fabricate to the necessary sufcae requirments, but require caotings with acceptable reflectivity only in a narrow bandpass. In this paper we will discuss the technical tradeoffs of using glancing incidence and normal incidence mirrors for EUV telescopes.

The reflectivity of grazing incidence W/C multilayer mirrors can be optimized by progressively refining structural features through sputter deposition parameter optimization. Beyond the configuration of system geometry, the deposition rate, substrate temperature and working gas pressure significantly affect the multilayer structure morphology. Of these parameters, working gas pressure has an overwhelming effect. The energy and distribution of sputtered adatoms, directly influenced by the sputtering gas pressure, affects the reactivity at and the reconstruction of vapor deposited surfaces. The interface abruptness is therefore affected by working gas pressure. The reduction in interfacial atomic intermixing (hence roughness) generally follows with decreased gas pressure. Correspondingly, the improved reflective efficiency becomes increasingly noticeable from hard to soft x-rays. Structural and reflectivity improvements in the W/C multilayer mirror system, characterized qualitatively using cross-section electron microscopy and quantitatively using x-ray diffraction, will be correlated to an optimization of the sputter deposition parameter - working gas pressure.

Atomic layer epitaxy is a new deposition technique which is ideally suited to producing multilayer x-ray optics with very small d-spacings. ALE allows monolayer control of film thickness, produces sharp interfaces and results in high crystalline perfection of multilayers. We have established criteria for selecting pairs of materials which can be deposited by ALE and have experimentally measured these criteria. We have also developed computer codes which predict x-ray reflectivity from multilayers deposited by ALE.

A grazing incidence solar X-ray telescope, SXT, will be flown on the Solar-A satellite in 1991. Measurements have been conducted to determine the focal length, PSF (Point Spread Function), and effective area of the SXT mirror. The measurements were made with pinholes, knife edges, a CCD, and a proportional counter. The results show the 1/7. character of the PSF, and indicate a half power diameter of 4.9 arc-sec and an effective area of 1.33 cm² at 13.3 Å (.93 keV). The mirror was found to provide a high contrast image with very little X-ray scattering.

This paper describes and illustrates a simple method of predicting the imaging performance of synchrotron mirrors from laboratory measurements of their profiles. It discusses the important role of the transverse coherence length of the incident radiation, the fractal-like form of the mirror roughness, mirror characterization, and the use of closed-form expressions for the predicted image intensities

Two types of grazing incidence ring resonators for use with free-electron lasers have been investigated. These cavities utilize off-axis conical and flat mirrors and have been designed to operate in the extreme ultraviolet region of the spectrum. In this paper, a design algorithm which calculates the mirror parameters for propagation of Gaussian TEMP mode beams in the two cavity types is presented.

Grazing incidence systems, such as extreme ultra-violet and X-ray telescopes, produce images which differ qualitatively from those of conventional normal incidence systems. Some of the more well known effects are increased scatter due to the short radiation wavelength, and pronounced diffraction patterns due to the high obscuration ratio of the system. However, a much less well known effect is the rapidly increasing intensity very near the center of the image. Within a substantial part of the image core, the intensity can be shown to increase inversely with the image radius ("1/r" behavior). This gives rise to an inherently minute Full-Width-Half-Maximum (FWHM) for the image. The measured FWHM in fact depends critically on the detector, all of which suggests that the FWHM is not a suitable image descriptor for grazing incidence systems. In this paper, we first review the well known scatter and diffraction effects. We then give some intuitive explanations for the less well known "1/r" behavior of the intensity, derive the mathematics to define the effect quantitatively, and give some examples.

Background in x-ray to in near-Earth orbits from low-energy electrons (<100 keV) has long been a source of concern. Recent data on low-energy electron populations and improvements in the modelling of the propagation of low-energy electrons through grazing-incidence optical systems now allows better quantitative estimates of the electron throughput of such systems to be made. The modelling which has recently been done with respect to the U.K. soft x-ray to (WFC) on ROSAT will be described. The results from the modelling will then be applied to several other missions using grazing-incidence optics and the implications discussed.

Orthonormal polynomials have long been used to describe optic surface errors. Previously, the product of Fourier and Legendre polynomials has been used to describe the surface errors of grazing incidence optics. We have applied an alternative set, Fourier-Fourier polynomials, to describe the surface errors. This set functionally differs from the Fourier-Legendre set in that each term has a finite bandwidth frequency spectrum. We discuss the advantages of this difference with respect to predictions of grazing incidence telescope performance based upon measured surface figure errors.

The rigid body motions and low frequency surface errors of grazing incidence Wolter telescopes are studied. The analysis is based on surface error descriptors proposed by Paul Glenn. In his analysis, the alignment and surface errors are expressed in terms of Legendre-Fourier polynomials. Individual terms in the expression correspond to rigid body motions (deCenter and tilt) and low spatial frequency surface errors of mirrors. With the help of the Legendre-Fourier polynomials and the geometry of grazing incidence telescopes, exact and approximated first order equations are derived in this paper for the components of the ray intercepts at the image plane. These equations are then used to calculate the sensitivities of Wolter type I and II telescopes for the rigid body motions and surface deformations. The rms spot diameters calculated from this theory and OSAC ray tracing code agree very well. This theory also provides a tool to predict how rigid body motions and surface errors of the mirrors compensate each other.

The ability to pipe beams of X-rays and energetic particles (protons, ions, and electrons) through thin, flexible, hollow, crystalline fibers has enormous potential as a therapeutic aid in the treatment of certain types of cancers. This report describes the theory of, and initial experiments with, the first fibers intended for the transmission of ionizing radiation.

We have developed a multi-facet retroreflecting mirror substrate structure which can be coated with a fresh aluminum film in an ultra-high vacuum (UHV) system and subsequently used for in situ reflectance measurements in the extreme ultraviolet (XUV). We utilize a gas discharge XUV source in combination with a 0.2 m Minuteman monochromator to illuminate the 9-facet mirror with a series of XUV wavelengths. The XUV beam is incident on each of the nine facets at 80 degrees (from normal). An imaging microchannel plate detector is utilized to measure both the incident beam and the retroreflected beam in the UHV chamber. Maintenance of an ultra-high vacuum level during the thin film deposition and the subsequent reflectance measurements provides assurance that the fresh aluminum film does not form an oxide surface layer which would adversly affect the XUV reflectance measurements. Results of these reflectance measurements will be discussed.

Accurate prediction of focal plane performance is difficult at x-ray wavelengths for grazing incidence optical systems with very highly obscured apertures like the SXT mirror assembly. For such instruments, geometrical models give way to diffraction based descriptions of performance. Because diffraction heavily influences the imagery of an x-ray system, the traditional image quality parameters of geometrical optics are not always appropriate quality critera. The definition and utility of the traditional image quality parameters have been a subject of recent discussion, along with the methodology of converting measurables into the parameters required by diffraction based theory. This paper describes a modeling approach that was used to set telescope surface specifications in order to achieve a desired encircled energy and spot size at an operating wavelength of 13.3Å. Assumptions that were made before fabrication will be presented first. Next, performance predicted by replacing many of these assumptions with actual parameters obtained from measurement of the as-built surfaces (for example the power spectrum of the mid and high spatial frequency figure errors) was compared to test data taken in the NASA/Marshall x-ray testing facility. Finally, an estimate was made of the rms spot size, from knife edge data. This is discussed in terms of its usefulness as a descriptor of telescope performance.

This paper covers the various techniques that are currently being used and developed to fabricate grazing incidence X-ray optics for the energy range from about 0.2 keV to 20 keV. Included will be diamond turning, thin foils, epoxy/carbon fiber replication, electroforming replication, and float glass/Kirkpatrick-Baez techniques.

For ESA's XMM Telescope three mirror modules, each consisting of 58 thin walled highly nested Wolter I mirrors, a large number of mirror shells are required. The specified performance of the XMM mirror modules require new design concepts and application of new technologies for the production of the lightweight mirror shells. Under ESA contract Zeiss leads an European industrial/scientific con-sortium to develop the technologies which allow production of real size XMM mirror shells by a dedicated metal/epoxy resin replication technique. In late 1988 the first full size XMM mirror shell was successfully replicated having the following characteristics: Total length: 600 mm Max. shell diameter: 400 mm Carrier material/thickness: CFRP/0.8 mm Replication layers: Gold/epoxy Total replicated mirror surface: 7500 cm2 Development, preparation and mirror shell replication are described. First results of the performance of the mirror shell after measurements and X-ray testing are presented.

The design concept of the mirrors for the ESA high throughput x-ray spectroscopy mission XMM is characterized by thin (< 1 mm) graphite epoxy shells as mirror structure and a replication technique to produce the mirror surface. The mirror microroughness is specified to σ < 0.5 nm (r.m.$), profile errors shall not exceed + 2.5 arc sec. An ESA research study has been performed by Zeiss and subcontractors (Dornier GmbH, Max Planck Institut fUr Extraterrestrische Physik/ Garching (MPE), University of Leicester, X-ray Astronomical Group, Dept. of Physics) to clarify whether graphite epoxy mirror structures are able to meet the tight XMM mirror figuring and surface requirements and which measures have to be taken to overcome the typical problems associated with composite materials used as mirror substrates:• Print-through of fibres and inner structure •Short term/long term stability• Water absorption and outgassing. The starting conditions and progress during development are described. The present status of optical and x-ray performance of replicated flat graphite epoxy mirrors is reported and aspects for further improvement of graphite epoxy mirrors will be discussed.

The present paper gives the requirements for the performance of X-ray mirrors at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. It is shown that the efficiency of synchrotron radiation experiments on next generation storage rings is optics-limited rather than source-limited. The effects of microroughness and slope errors as well as thermal and mechanical aspects of mirror cooling are discussed. Finally some ideas for research and development are outlined.

Unique mechanical and optical design features of this solar x-ray telescope were required to survive launch, and to achieve excellent imagery over a large field of view. These design features placed exceptional demands on all of the manufacturing and measurement processes. Survivability dictated use of a monolithic mirror assembly with both optical surfaces generated and polished on the same substrate. Good performance dictated a maximum axial separation of 5 mm between these surfaces (H-1 and H-2), placing difficult restrictions on the generation, polishing, and smoothing operations. The wide field requirements of a solar imager placed unprecedented tolerances on measurement and control of H-1 to H-2 alignment, delta-delta Radius, and absolute axial sag, because of the short axial dimension. An additional portion of the error budget for delta-delta Radius had to be given to large on-orbit thermal variations, tightening this specification even further.

We report on the progress being made on the mirror array telescope for high energies (MARTHE) project. As a first step, we are producing small mirror flats and full-size Wolter I mirrors that are lacquer coated (mandrels) and then coated with gold or palladium. We present the up-to-date results of fabricating and testing these mirrors. Currently, we can provide results on the micro-roughness, macro-figure, X-ray scattering and reflectivity up to 8 keV from flats and Wolter I mirrors as well as optical measurements of the flats. We are also trying to extend the technology to work at energies up to 40 keV.

The first satellite in a planned series of Soviet X- and gamma ray satellites will be equipped with two high throughput telescopes to be delivered by the Danish Space Research Institute. The thin foil tech-nology was originally developed by P. Serlemitsos at Goddard Space Flight Center, U.S.A. Our modification of this design is optimized with respect to high energy throughput of the telescope. The mechanical design and the status of the surface preparation technologies are described. Various X-ray and optical test facilities for the measurement of surface roughness, "orange peel", and figure errors are described. An optical parallel beam has been established and results from the first mounted mirrors are discussed. The design goal is an angular resolution of 2 arcminutes (HEW). The first results seem to indicate that this is feasible and the possibility of going down to 1.5 arcminutes exits.

Grazing incidence x-ray optics for x-ray astronomical applications are used outside the earths atmosphere. These devices require a large collection aperture and the imaging of an x-ray source which is essentially placed at infinity. The ideal testing system for these optical elements has to approximate that encountered under working conditions, however the testing of these optical elements is notoriously difficult with conventional x-ray generators. Synchrotron Radiation (SR) sources are sufficiently brilliant to produce a nearly perfect parallel beam over a large area whilst still retaining a flux considerably higher than that available from conventional x-ray generators. A facility designed for the testing of x-ray optics, particularly in connection with x-ray telescopes is described below. It is proposed that this facility will be accommodated at the Synchrotron Radiation Source at the Daresbury Laboratory in the U.K.

We present X-ray measurements of total reflectivity and scattering from gold coated foils. The foils are two sorts of 0.3 mm thick dip-lacquered aluminum, 0.125 mm thick plastic (Upilex) and 0.5 mm thick dip-lacquered nickel. The analysis of the data show a high reflectivity for all but the plastic foil, and only small microroughness (-10A at lengthscales below -0.1 micron), evidenced by low resolution scat-tering measurements.

The Extreme-Ultraviolet Imaging Telescope (EIT) will be launched on-board the Solar Heliospheric Observatory (SOHO) in 1996. Images in four narrow bandpasses at wavelengths ranging from 17 to 31 nm will be obtained using normal incidence multilayered optics deposited on quadrants of a Ritchey-Chretien Telescope. The design of the telescope is discussed in detail and actual performances measured on a 2/3 scale mock up are reported.

The High Throughput X-ray Spectroscopy Mission XMM is the second cornerstone in ESA's long term space science programme and is due for launch in 1998. This long duration observatory for X-ray astrophysics has at its heart three heavily nested Wolter 1 grazing incidence X-ray mirror modules, which will provide a dramatic increase in collecting area over previous and contempory missions. This large aperture when coupled with an optics spatial resolution of between 15 to 30 arc sec (HEW) and sensitive X-ray cameras and spectrometers will allow a major advance in astrophysics at the turn of the century. The development programme for the X-ray optics is described and recent results presented. A detailed description of the focal plane instrumentation is also provided. The selection of this payload has just been approved by ESA's Science Programme Committee.

The ROSAT project is an international collaboration between W.Germany, the United Kingdom and the USA. The satellite, due to be launched in February 1990, carries a payload of two co-aligned imaging telescopes: the German X-ray Telescope (XRT) which operates in the soft X-ray band (0.1-2 keV or 6-100 Å) and the UK Wide Field Camera (WFC) which operates in the XUV band (0.02-0.2 keV or 60-600 Å). ROSAT will perform two main tasks in its anticipated 2-4 year lifetime: a 6-month all-sky survey in the soft X-ray and XUV bands followed by a programme of pointed observations for detailed studies of thousands of individual targets. In this paper we review the design and performance of the WFC. The instrument is a grazing incidence telescope comprising a set of 3 nested, Wolter-Schwarzschild Type I, gold-coated, aluminium mirrors, with a microchannel plate detector at their common focus. Thin plastic and metal film filters define the wavelength passbands.

The Extreme Ultraviolet Explorer (EUVE) is a NASA funded astronomy mission which will operate in the 70 -760 Å band. The science payload, which has been designed and built by the Space Sciences Laboratory at the University of California, Berkeley, consists of three grazing incidence scanning telescopes and an EUV spectrometer/deep survey instrument. We give details of the planned mission profile together with an overview of the instrumentation which comprises the science payload. Topics such as the thermal design, contamination control and details of the electronics system are discussed. Finally we review the results of the calibration of the various sub-systems that make up the EUVE instrumentation and discuss the calibration plan for the integrated EUVE instruments which began in June 1989 at the Berkeley EUV Calibration Facility.

XMM is a highly nested (58 individual shells) Wolter-I type X-ray telescope with a focal length of 7.5 m. The specified resolution (HEW) is 30 (goal 20) arcsec. In order to qualify single mirror shells and align and assemble the whole mirror module in a reasonable time it is inevitable to apply fast test and strongly converging alignment procedures. By means of two scanning laser beams intra- and extrafocal images of two mirror shells will be registered on a CCD-camera coupled to an image processing PC. One of the mirrors is already glued and serves as a reference while the second one has to be aligned yet. From the data axial and lateral focus positions as well as focus dimensions are calculated. A feed back loop then activates a set of actuators coupled to the mirror to be aligned. In an iterative way the alignment status of this mirror will be optimized. Finally, this mirror is cemented under optical control. First results from a basic test setup with only one mirror will be presented.

Measurements in our laboratory have recently shown that the pulse quantum yield (counts/photon) of CsI X-ray photocathodes, measured near grazing incidence, depends on the linear polarisation state of the incident beam. These results have implications both for the fundamental understanding of the X-ray photoeffect and, since CsI is well-known as a cathode material of high (unpolarised) quantum efficiency in the 0.1-1.0 keV band, for the development of high throughput astronomical X-ray polarimetry. This paper, concentrating on the latter topic, describes the practical accomodation of a Photoemission Polarimeter at (or near) the focus of a satellite X-ray telescope. Problems of device format, instrumental polarisation and data compression are discussed with reference to the Composite X-ray Polarimeter recently proposed for the ESA XMM mission. Examples of the sensitivity of this instrument are given. In the second part of the paper, our most recent laboratory measurements are presented. These concern the variation in the number of X-ray photoelectrons with the polarimetric azimuth of a CsI cathode.