Total absolute photoabsorption cross sections were measured at 1 keV to 40 keV for Fe, Ni, Sn, Ta, Pt, Au, Pb and U. Overall measurement uncertainties were 3%, less than 2% of which were statistical. The measurements tested widely-used theoretical and experimental tables. They favored relativistic Hartree-Slater atomic calculations. Agreement with theory was typically 5% or better, except near the absorption edge energy region with EXAFS peaks. The measured peak and valley magnitudes for the solid samples ranged from 0% to 20% (with an average of 10%) above the atomic calculations for Fe and Ni. Discrepancies with experimental tables, at energies below 6 keV, were 10% to 40%. Authors of widely-used tables have been fraught with problems where there were few or no prior measurements, only interpolations and,theory. The present measurements used samples from a few hundred to a few thousand μg/cm2, such that the mean free path thicknesses, ppx, were 1 and 3 at 1.5 keV. Samples were vapor-deposited 440, and floated off of, optically flat glass slides. Their weights per unit area, μx g/cm4, were determined within 2% or 3%. Thicker samples, of known weights per unit area, were used for the higher energy measurements. The ratio of ppx for thick and thin samples tested px for the thin samples. Back-scattered protons and alpha particles, as well as ion microanalyses, were used to test the samples' purity. Uranium deposits were sandwiched between two beryllium layers to impede surface oxidation. The transmission measurements were taken with a demountable x-ray tube, vacuum crystal monochromator and flow proportional counter, using slits that provided a narrow-beam geometry.

Normal incidence reflection multilayer optics show promise in enabling high spatial resolution (better than 1 arcsec) and low to moderate spectral resolution (λ/▵λ = 8 - 200) imaging in the soft X-ray/XUV spectral regime (40 - 300 Å). In preparation for a Solar X-Ray/XUV Sounding Rocket observation in late 1986 which will utilize normal incidence reflection X-ray optics, several multilayer coatings have been deposited on concave and convex spherical surfaces. The coatings are tungsten-carbon and molybdenum-silicon multilayers and are designed for normal incidence reflection at wavelengths ranging from 44 Å to 304 ⇔. The multilayers havebeen characterized in the laboratory in normal and glancing incidence modes using 1.54 Å to 114 Å radiation. In addition to measuring spectral resolution and absolute reflectivities, multilayer-coated optics have been successfully tested in the imaging mode. This paper will review the measured characteristics of the multilayer coatings and optics and will describe the optical configurations planned for the upcoming solar observation.

High reflectance mirrors are difficult to achieve in the extreme ultraviolet (EUV) and we have found that one of the principle reasons is the presence of contamination layers on the surface of these reflectors.¹ We have begune7study of these contamination layers that form even in an ultra-high vacuum (UHV) system. ' Our initial study consists of monitoring the growth of these contamination layers on various metal surfaces utilizing Auger electron spectroscopy (AES). A principal conclusion from this work is that the rate of growth of oxide and carbon contamination layers on Al, Si, and Rh is greatly enhanced if the ion gauges and Auger filaments are operating. Reflectance measurements on Rh at 11.3 nm also indicate the presence of significant carbon contamination on samples exposed to air. In addition, we find that oxide growth on Ag is negligible and carbon contamination is minimal.

General algorithms have been developed for interpreting X-ray fluorescence (XRF) data from single and multilayer metal films to yield precise values for both thickness and composition. As an example, the relative precision for a replicate analysis of a multilayer Al-Ti-Cu (substrate) sample was measured to be 0.6% (lo) for a 14 micron Al layer and 2.4% (lσ) for a 65OÅR Ti underlayer. Several examples showing the rapid, nondestructive nature of the analysis will be presented.

Multi-Anode Microchannel Array LMAMA) detector systems with formats of 256 x 1024 pixels and active areas of 6 x 26 mm2 are now under evaluation at visible, ultraviolet and soft x-ray wavelengths. Very-large-format version2s of the MAMA detectors with formats of 2048 x 2048 pixels and active areas of 52 x 52 mm are under development for use in the NASA Goddard Space Flight Center's Space Telescope Imaging Spectrograph (STIS). Open-structure versions of these detectors with CsI photocathodes can provide a high-resolution imaging capability at extreme ultraviolet (EUV) and soft x-ray wavelengths and can deliver a maximum count rate from each array in excess of 106 counts s-I. In addition, these detector systems have the unique capability to determine the arrival time of a detected photon to an accuracy of 100 ns or better. The construction, mode-of-operation and performance characteristics of the MAMA detectors are described and the program for the development of the very-large-format detectors is outlined.

Charge coupled device arrays (CCDs) with low noise, small pixel size and high charge storage capacity are available at relatively low cost. Because of this, CCDs are finding increasing use in imaging applications. In this paper we will discuss the performance of a TI-4849 CCD array in an x-ray camera to be used for high-resolution synchrotron radiation tomography. The x-ray image is converted to visible light on a phosphor coated optical face plate which is imaged by a thermoelectrically cooled CCD. The measured modulation transfer function (high-contrast MTF) will be presented for this system. We will describe procedures for choosing and preparing the optimal phosphors for x-ray imaging. Advantages and limitations of CCD arrays over other detectors for tomographic applications will also be discussed.

The development of layered synthetic microstructure x-ray optic arrays to serve two distinct roles in high temperature plasma experimental research will be described. An optic array of large active area (500 cm2) provides the basis for a fusion product-immune x-ray imaging system (XIS) diagnostic that will be experimentally evaluated at the Princeton Plasma Physics Laboratory (PPPL) Tokamak Fusion Test Reactor (TFTR). The array is formed by end-to-end assembly of concave-cylindrical multilayer components along a parabolic trace. Our experience to date in the physics and engineering design of the array will be described.*

The isoangle and isobragg are new concepts used in mapping loci of incident and reflected rays associated with a dispersive reflector. An isoangle is a line joining the points of incidence at which the angle of incidence of rays from a point source is the same. An isobragg is the line joining the points of intersection at any surface by rays of the same wavelength that have been reflected according to Bragg's law. Their patterns provide an understanding of why and where we use dispersive multilayered optics in x-ray monochromators and spectrometers with Rowland circle geometry. They have led to the design of an x-ray focusing ring for electron spectroscopy for chemical analysis (ESCA) instrumentation and the possibility of a design for a scanning x-ray microscope.

Two-dimensional curved surfaces, which may be suitable for X-ray reflective. lenses of the multilayer type, have been produced using polished. single crystal {110} silicon. wafers. The curvature was achieved using stressed thin. films of grown silicon. dioxide and deposited. silicon nitride. In addition to basic experimental studies with planer structures to determine stress values and predictive equations, the paper describes several methods used for stressing a preferentially etched deep, groove silicon structure. The latter structure is needed for non cylindrical surfaces. Effects which limited the predictability and surface quality of the curved surfaces were the thickness variation of the silicon, wafers and the occurrence of dislocation slip lines on the polished. surface- The latter was primarily due. to stress on {1111 'lanes at high temperature.

There is increasing interest in the application of multilayers to figured x-ray optics. Two concepts in design approach are presented. The requirements for image formation with a multilayer device are discussed. A geometrical approach is used. The possible affect of multilayers on image quality are studied. Models for the reflectivity of x rays by multilayers are compared briefly.

An assessment of the imaging properties of multilayer x-ray imaging systems with spherical surfaces has been made. A ray trace analysis was performed to investigate the effects of using spherical substrates (rather than the conventional paraboloidal/ hyperboloidal contours) for doubly reflecting Cassegrain telescopes. These investigations were carried out for mirrors designed to operate at selected soft x-ray/XUV wavelengths that are of significance for studies of the solar corona/transition region fran the Stanford/MSFC Rocket X-Ray Telescope. The effects of changes in separation of the primary and secondary elements were also investigated. These theoretical results will be presented as well as the results of ray trace studies to establish the resolution and vignetting effects as a function of field angle and system parameters.

High resolution x-ray microtomography has been established at the synchrotron radiation source at Daresbury Laboratory, U.K. A high precision mechanical stage with two translational and one rotational degree of freedom has been constructed, and fully characterised by mechanical metrology; overall precision is better than 0.5 μm. Collimation of the incident synchrotron radiation beam through a 4 pm aperture has been obtained, giving 2 μm overall spatial resolution. Results have been obtained using monochromatic radiation at both 1 angstrom and 0.37 angstrom wavelengths, on human bone fragments and on sintered alumina ceramics.

A 2" x 4" ReW-C multilayer mirror (d = 33. Å) is used to reflect a narrow bandwidth x-ray beam from the emission spectrum of a W-anode radiographic tube. Theoretical reflectivity curves and measured reflected spectra are presented. The rejection of most x-ray energies outside of a limited bandwidth permits the x-ray tube to operate at a higher (more efficient) voltage than is possible with conventional radiographic beam filters. A contrast phantom was imaged using a slit scan system with a film-screen x-ray detector. An array of mirrors (multiple slit scanning) is considered as a means of reducing tube heat loading. The ability to select either the Mo K or K characteristic x-ray may offer an alternative to a W-anode Bremsstrahlung spectrum for mammography and soft tissue radiography.

There are problems in the measurement of thickness of field-applied thick polymer coatings on iron and aluminum substrates. New ways are sought to accomplish this. X-ray fluorescence (XRF) offers a potential measurement technique through assessment of the change in x-ray signal peak intensity on the continuum of radiation as a function of energy. Panels with varying thicknesses were tested. In general, the data show that as coating thickness increases so does the XRF intensity. It has also been found that by adding a zinc marker to the coating on an aluminum substrate a broader spread of intensity readings was obtained than with an iron marker. Homogeneity of the marker in the coating appears to be critical to this potential measurement system, Further research is needed to document the use of XRF instrumentation as a tool for coating thickness measurement.

A second generation scanning soft x-ray microscope is under construction, designed to utilize the dramatic increase in source bightness available at the soft x-ray undulator. The new instrument is expected to reduce image acquisition time by a factor of about 100, and to improve resolution, stability, and reproducibility.

A soft X-ray camera and image processing system has been constructed to provide measurements of the internal shape of high temperature tokamak plasmas. The camera consists of a metallic-foil-filtered pinhole aperture and a microchannel plate image intensifier/convertor which produces a visible image for detection by a CCD TV camera. A wide-angle tangential view of the toroidal plasma allows a single compact camera to view the entire plasma cross section. With Be filters 12 to 100 m thick, the signal from the microchannel plate is produced mostly by nickel L-line emissions which originate in the hot plasma core. The measured toroidal image is numerically inverted to produce a cross-sectional soft X-ray image of the plasma. Since the internal magnetic flux surfaces are usually isothermal and the nickel emissivity depends strongly on the local electron temperature, the X-ray emission contours reflect the shape of the magnetic surfaces in the plasma interior. Initial results from the PBX tokamak experiment show clear differences in internal plasma shapes for circular and bean-shaped discharges.

This paper describes a large grazing incidence x-ray telescope that is being prepared for use in a spectrometer for x-ray astronomical observations. The telescope is figured by diamond turning and polished by applying an acrylic lacquer that is overcoated by a thin film of tungsten to provide high x-ray reflectivity. The current status of our research in multilayer deposition is presented and some astronomical applications of multilayer mirrors are described.

An X-ray telescope for the LAMAR instrument has been designed, built and tested at the Smithsonian Astrophysical Observatory. In addition, telescope performance has been verified at the NASA Marshall Space Flight Centers long X-ray beam facility. After X-ray testing and data reduction is complete, the telescope will undergo vibration testing. Post-vibration visible light tests will then verify no change in performance. The design and fabrication of this high-throughout Kirkpatrick-Baez geometry telescope incorporates the use of advanced composite materials (aluminum-graphite/epoxy) to provide a thermally stable structure. A computerized figure formation system is used to attain the approximate parabolic curve of each optic. Each optic is supported by ten titanium flexures to provide the necessary decoupling between the stiff structural support module and the glass mirrors. The design, analysis and fabrication` ofthis module will be described, as well as the numerous problems encounted and the solutions developed, in this protoflight project.

X-ray astronomy, both solar and celestial, requires long focal length optical systems to provide high spatial resolution images and to be used as feeds for spectrometers. In typical experimental situations, the physical size is restricted and grazing angles must be kept at or below one degree. Grazing incidence secondary optics are an alternative to long focal length primary mirrors. We have designed, fabricated and tested a system which employs a secondary with externally polished hyperboloid-hyperboloid surfaces. It is to be used in conjunction with an existing Wolter-I primary. The system has been designed for high resolution imaging of the solar corona with the goal of producing images electronically with the same spatial resolution as achieved at the primary focus with film. The secondary optic is located in front of the primary focus, as in a Galilean telescope, and provides a magnifi1ation of approximately four. The combined system has a plate scale of 26.0 pm (arc sec) , effective focal length 5.4 m, and is contained within an instrument length of 1.9 m. The design, tolerance specification and fabrication techniques are described. The performance of the system at X-ray wavelengths has been determined experimentally and is compared with theoretical results produced by ray tracing.