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This work addresses the issue of X-ray monitoring for astrophysical applications. The proposed wide-field optical system has not been used in space yet. The proposed novel approach is based on the use of 1D "Lobster eye" optics in combination with Timepix X-ray detector in the energy range 3 - 40 keV. The proposed project includes theoretical study and a functional sample of the Timepix X-ray detector with multifoil wide-field X-ray "Lobster eye" optics. Using optics to focus X-rays on a detector is the only solution in cases the intensity of impinging X-ray radiation is below the sensitivity of the detector, e.g. while monitoring astrophysical objects in space, or phenomena in the Earth's atmosphere. The optical system could be used in a student rocket experiment at University of Colorado. Ideal opportunity is to extend the CubeSat of Pennsylvania State University with the hard X-ray telescope demonstrator consisting of an optical module and Timepix detector.

High resolution spectroscopy is the most favored objective of the next X-ray astronomy mission. A longer term goal is the development of a very large area X-ray telescope whose angular resolution and effective area are superior to the Chandra X-Ray Observatory. Adjustable X-ray optics with thin piezoelectric coatings is a methodology that may be capable of accomplishing that goal. It consists of applying piezoelectric coatings to the rear of a mirror substrate, which will be thermally slumped to the approximate figure. The figure is optimized by applying voltages to the piezoelectric coatings. Near term spectroscopy mission can benefit from higher angular resolution and a Kirkpatrick-Baez telescope should be considered as an alternative to the Wolter telescope. Adjustable X-ray optics technology should be very effective in refining the resolution of a KB telescope. When the thermally slumped mirrors of either the front or rear section are assembled and illuminated by a parallel visible light or X-ray beam line, line images formed by individual mirrors can be isolated by a moveable slit. With the piezoelectric controllers acting in only dimension the figure of each mirror can be optimized sequentially completely under computer control. The front and rear sections can be tuned independently and then joined with rather lenient tolerances. Dispersing along the 45 degree direction between the two orthogonal KB axes reduces the effect of scattering and figure errors similar to what is accomplished by using only part of the azimuth of a Wolter mirror.

X-ray astronomy grazing incidence telescopes use the principle of nested shells to maximize the collecting area. Some of the more recent missions, such as XMM-Newton [1], have used an electroformed nickel replication (ENR) process [2] to fabricate the mirror shells. Upcoming missions, such as Spectrum-Rontgen-Gamma [3] and Focusing Optics X-ray Solar Imager [4] , also use the electroforming process to fabricate nested shell grazing incidence X-ray telescopes. We present recent results on fabrication of replicas with multilayer coatings from Wolter-1 mandrels using a new hardcoat release material to simplify and improve this electroforming process.

The soft X-ray band hosts a larger, more diverse range of variable sources than any other region of the electromagnetic spectrum. They are stars, compact binaries, SMBH's, the X-ray components of Gamma-Ray Bursts, their X-ray afterglows, and soft X-ray flares from supernova. We describe a concept for a very wide field (~ 4 ster) modular hybrid X-ray telescope system that can measure positions of bursts and fast transients with as good as arc second accuracy, the precision required to identify fainter and increasingly more distant events. The dimensions and materials of all telescope modules are identical. All but two are part of a cylindrical lobster-eye telescope with flat double sided mirrors that focus in one dimension and utilize a coded mask for resolution in the other. Their positioning accuracy is about an arc minute. The two remaining modules are made from the same materials but configured as a Kirkpatrick-Baez telescope with longer focal length that focuses in two dimensions. When pointed it refines the hybrid telescope's arc minute positions to an arc second and provides larger effective area for spectral and temporal measurements. Above 10 keV the mirrors act as an imaging collimator with positioning capability. For short duration events this hybrid focusing/coded mask system is more sensitive and versatile than either a 2D coded mask or a 2D lobster-eye telescope. Very wide field X-ray telescopes have become feasible as the ability to fabricate large area arrays of CCD and CMOS detectors has improved. This instrument's function in the soft X-ray band is similar to that of Swift in hard X-ray band and there are a greater variety of fast transients in the soft X-ray band. An instrument with considerably more sensitivity than current wide field X-ray detectors would be compatible with a modest NASA Explorer mission., Comment: 15 pages, 5 figures, To be presented at SPIE Conference 8147 "Optics for EUV, X-Ray, and Gamma-Ray Astronomy V", Aug.21-25, 2011

Generation-X is required to be an X-ray observatory with 50 m2 effective collecting area and 0.1 arcsec half-power diameter (HPD) angular resolution at 1 keV. It is conceived that a launch vehicle such as that studied for the Ares V will carry a monolithic 16-m-diameter mirror to the earth-sun L2 point. Even with such a vehicle, the reflectors comprising the ≈ 250 nested shells must be extremely light-weight. Therefore their figure and alignment cannot be achieved on the ground, and likely could not be maintained through the launch environment. We will present a conceptual solution to those constraints: adjustable X-ray optics, as a case of "adaptive" optics where the stability once in orbit should require adjustments no more frequently than yearly. The figure would be adjusted via thin-film actuators deposited directly to the back (non-reflecting) side of each element. This bi-morph configuration would impart in-plane strains via the piezoelectric or electrostrictive effect. Requirements of the adjustment are to the order of a few nanometer precision. Each shell, and each module, must also be aligned, to tolerances of about 0.1 micrometer. We conceive that on-orbit data would be acquired by a built-in Hartmann system for the alignment adjustments and low-order figure, and by ring profile measurements of a very bright celestial X-ray source to correct figure errors up to the mid-frequency range of several hundredths cycles mm −1 .

The use of depth-graded multilayer coatings is foreseen in several future X-ray telescopes (e.g. Hexit-Sat/NHXT, NuSTAR, IXO, NeXT), in order to extend to higher energies (up to 80 keV) the focusing capabilities of present day telescopes, like Chandra and XMM/Newton, that are operative in the soft X-ray band (0.1-10 keV). The deposition of multilayer coatings is a difficult process, in which a good control of the individual layer thickness is required. The process must also be stable for the long time needed (several hours). The main issues are the accuracy of the film (stability of the process), interfacial and surface roughness, the lateral homogeneity and the long-term stability of the film. Physical properties of the film, like the density or the crystallicity are also important. The analysis of reflectivity measurements is an important tool to study the structure of multilayer samples, investigating in a non-destructive way the whole properties of the film down to the deepest layers. Nevertheless the analysis of data is not easy, neither standardized. Two samples were realized using different materials (Pt/C and W/Si). The film structures were designed to be representative of broad angular/energy band multilayer coatings foreseen in hard X-ray focusing telescopes. Their reflectivity was measured for several energies in the 40-130 keV range as a function of the reflection angle. The High energy reflectivity data are compared with the theoretical expectations derived from low-energy (8.04 keV) measures acquired after the deposition.

X-ray astronomy grazing incidence telescopes use the principle of nested shells to maximize the collecting area. Some of the more recent missions, such as XMM-Newton, have used an electroformed nickel replication process to fabricate the mirror shells. We have been developing coatings to simplify and improve this electroforming process. This paper discusses our most recent results from studies using TiN as a mandrel hardcoat in the electroforming process of fabricating nickel shell optics. The results indicate that nickel replicas separate easily from the TiN coated mandrel, and little (if any) degradation of the mandrel occurs after more than 20 replications. AFM characterization of the mandrel and replica surfaces is shown. Preliminary results are also included from studies which use this same process to replicate multilayer coatings; these results indicate no change in the multilayer stack after separation from the mandrel.

Gamma ray bursts have become as important as supernova in astrophysics and cosmology and they should be studied with the same amount of diligence and continuity. Most of the types of telescopes and detectors needed already exist and in fact have already been in space. The addition of a very wide field, high angular resolution X-ray telescope would open a much larger window to bursts whose spectra are soft, either intrinsically or as a result of high redshift. Sensitivity in the X-ray band also benefits from the large number of photons of the X-ray afterglow. To fill that role we describe a telescope that is a lobster-eye optic in one dimension and a coded aperture in the other. It has larger area and bandwidth than a two-dimensional lobster-eye optic but is subject to more background. A permanent site that can accommodate a complete set of instruments that covers the entire energy range from soft X-ray to gamma ray would be preferable to the current practice of launching new spacecraft periodically with instruments that cover only part of the range. Astronomers generally favor free space, over the Moon as an observatory site. However, the architecture of a gamma ray burst observatory is more compatible with a lunar base than is the typical observatory. The instruments can be delivered gradually and perhaps at lower cost to the astrophysics budget through an Earth-Moon transportation system that is supported by the Exploration program.

The 0.5 arcsec angular resolution of the Chandra X-Ray Observatory is likely to be the best that a grazing incidence telescope with substantial collecting area will ever attain. We describe a concept for a telescope composed of diffractive and refractive components that transmit rather than reflect X-rays. Therefore, its angular resolution would be relatively insensitive to figure errors and surface roughness. With appropriately selected values for the two focal lengths the chromatic aberration that is inherent in both the diffractive and refractive components individually would compensate each other within a limited but not insignificant energy band. The system has a focal length of about 10 4 km because the refractive component is rather weak. The long focal length requires a very demanding type of formation flying between an optics spacecraft and a detector spacecraft. We simulate the simplest diffractive/refractive imaging system where chromatic aberration is corrected to first order at 6 keV. The angular resolution is expected to be better than a miliarcsec within a 10 % bandwidth. The energy band could be broadened either by employing an array of smaller systems with the same total area or by modifying the diffractive component in situ. The components are lightweight, not difficult to fabricate and can probably be made in a machine shop. We also consider possible sites for the system.

No future X-ray telescope is likely ever to have angular resolution significantly superior to the Chandra X-Ray Observatory without adopting a new technology. We consider focusing systems based upon diffraction and refraction rather than grazing incidence reflection. The elements are Fresnel zone plates and refractive lenses in configurations where chromatic aberration is corrected over a finite bandwidth. This technique is likely to be especially effective in the intermediate regime between the 0.5 arcsec capability of the Chandra telescope and the one-tenth microarcsec resolution required for the NASA "Vision Mission" entitled the "Black Hole Imager." Diffractive/refractive systems can also be configured as high throughput flux concentrators for third generation X-ray timing studies and non-dispersive spectroscopy. They may also have an important role in very high resolution spectroscopy. Because these elements focus by transmitting X-rays at normal incidence they can be extremely lightweight compared to grazing incidence telescopes. Furthermore the figure accuracy and surface smoothness are much less critical. On the other hand diffractive/refractive optics are characterized by chromatic aberration, which can be corrected only in small wavelength bands. Focal lengths range up to 105 km making the application of diffractive/refractive X-ray optics to astronomy dependent upon the development of technology for formation flying of very widely separated spacecraft.

The NASA's Constellation X-Ray Mission consists of a Soft X-Ray Telescope (SXT) based on large collecting area optics plus a focusing Hard X-Ray Telescope (HXT) operating between 8 and 70 keV and possibly at even higher energy. The Con-X HXT will have a focal length of 10 m and graze angles are small (0.25 - 0.1 deg). The substrates will be coated with multilayers to enhance the reflectivity but single heavy element coatings are an alternative for the small diameter substrates of the set. Twelve copies of the HXT are distributed evenly among the four Con-X spacecrafts. With multiple telescopes it is appropriate to consider electroforming, the replication process used successfully by Beppo-SAX, JET-X/SWIFT, and XMM-Newton, to produce their substrates. The important feature of the technique is that for mirrors with aperture diameters less than 40 cm also with thin substrates it is possible to achieve good angular resolution, which is important for obtaining high signal-to-noise ratios in deep observations and imaging extended sources. We review the main results of our development study devoted to proving the feasibility of the process for the Con-X/HXT, with particular stress on demonstrating, not only by theoretical considerations but also presenting an important experimental proof, that we can satisfy the severe mass constraints of the mission still maintaining good imaging capabilities.

The high rate at which importatn results are emanating formthe Chandra X-ray Observatory heightens our appreciation of the significance of high angular resolution telescopes in x-ray astronomy. However, the Chandra telescope is probably the last member of a line of high resolution telescopes with a conventional architecture. Qualitative improvement upon Chandra's resolution requires a new technology. We discuss a promising approach that is capable potentially of achieving microarcsecond resolution, possibly the highest angular resolution in astronomy of any wavelength band. It is based upon x-ray optics that focus by transmission at normal incidence rather than by reflection at grazing incidence. Its components are refractive lenses and Fresnel zone plantes. Extreme chromatic aberration is intrinsic to these devices but it can be overcome in small wavelength intervals above 2 keV with a technique described by Van Speybroech and by other methods. Like x-ray interferometry these systems have extremely long focal lengths and require 'formation flying' consisting of precise positioning between the optics and detector that be aboard separate spacecraft spaced far apart. However, it is less demanding of accuracy in formation flying than x-ray interferometery. These systems have much lower mass than grazing incidence telescopes with comparable collecting area.

There is broad interest in a next generation timing mission to succeed the PCA of RXTE which will provide more effective area than its 0.6 square meters and much better energy resolution. Currently prospective missions are, like the PCA, based upon large area detectors. Serious consideration should also be given to a focusing system. The focusing system would be a modular array of relatively small diameter imaging telescopes or concentrators with solid state detectors in their focal planes. For areas exceeding a square meter a focusing system could actually be less complex, more reliable, and for one particular optical design perhaps not much more massive. The total detector area would be only a few percent of the telescope aperture, which makes the acquisition of detectors much less challenging. Today it is possible to obtain commercially a sufficient number of detectors with good energy resolution for all the focal planes of the focusing array. They require only modest cooling and that could be accomplished passively in space. Several optical designs are possible. The disadvantages of an optical system are larger mass, more difficultly obtaining broad bandwidth, smaller field of view, and larger volume to accommodate the focal length distance and a larger diameter. On the other hand, the focusing system is more sensitive to fainter sources, is much more efficient below 2 keV, is less sensitive to background and is likely to be less costly overall than an array of solid state area detectors with equally good energy resolution.

We report the results obtained during the second phase of a program which consists of comparing the performance of different multilayer material combinations. These coatings will be used to extend the bandpass of current hard X-ray optics toward 100 keV, an order of magnitude higher than present technology. The materials studied here are W/Si, Pt/C, and W/C. A comparison of the performance of depth graded multilayers of these different materials at energies 30-80 keV was undertaken. Specular reflectivity data were acquired at 30-80 keV using the X17B1 beamline of the National Synchrotron Light Source. Reflectivity versus energy plots showed a high enough reflectivity for the bandpass of interest at grazing angles typical for hard x-ray telescope mirror shells. The next phase of our program will continue with similar high-energy pencil beam measurements on multilayer coated telescope prototype shells.

We present the results of a study of the influence of the deposition process parameters on the X-ray reflectivity of multilayer mirrors for applications at energies above 10 keV. The coating process used is DC magnetron sputtering and we have begun an optimization analysis for two material combinations: W/Si and Pt/C. The following process parameters were considered: argon pressure, distance between cathodes and substrate, and sputtering cathode currents. The samples are coated on 2' polished silicon wafers and their X-ray reflectivity is measured by performing a specular scan with an 8.05 keV (Cu K-alpha) X-ray beam. The reflectivity scans were analyzed with the IMD software and the fitted interface roughness values were correlated with the deposition parameters. The analysis of variance (ANOVA) statistical treatment of the data allows the determination of the contribution of each process parameter to the reflectivity and establishes which of the parameters need tighter control.

Estimates of background in CZT detectorsi indicate that even with the beneficial concentration of a focussing telescope measurements in the 20 to 100 keV band of the Constellation X-ray Mission's HXT will become background limited after several thousand seconds of observing. This time is less than the expected exposure of most measurements. Consequently the sensitivity of most if not all observations of the HXT will be background limited. Therefore, the angular resolution should be as good as possible as long as the effective area remains high. We are pursuing a method for fabricating telescopes for thetwelve units of HXT that consists of electroforming integral shell substrates, a process that has been highly developed for XMM. We are attempting to adapt this method to higher energy X-rays by employing multilayer coatings, and smaller graze angles, and also reduce the mass of the telescopes from the XMM prescription by employing stronger, lighter alloys. The resolution that XMM has achieved, 15" HPW is an indication of the resolution we can expect.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In addition to high resolving power in the traditional x-ray band, the Constellation X-ray scientific goals require broad bandpass, with response extending to E >= 40 keV. To achieve this objective, Constellation-X will incorporate a hard x-ray telescope (HXT) based on depth graded multilayer- coated grazing incidence optics and position-sensitive solid state detectors. This paper describes the HXT performance requires, provides an overview of the HXT optics and detector technology development efforts, and present example designs.

The imaging x-ray telescopes in current use mostly have limited field of view. The alternative x-ray optics geometries achieving very large fields of view have been theoretically suggested in the 70's but have been not constructed and used so far. We review the design and basic properties of the wide-field x-ray optical system based on one- and two-dimensional lobster-eye geometry and suggest technologies for their development and construction. First results of the development of replicated x-ray reflecting cells for use in 2D x-ray optics of Angel lobster eye type are presented and discussed.

We describe a method of building and deploying an ultra high throughput x-ray observatory with 2 by 10 5 cm 2 of effective area for the era following the Constellation X-ray Mission and XEUS. It is based upon a single focus telescope. Replacing and adding detectors are possible. Instead of an optical bench, the detector uses electric propulsion with plasma thrusters and ion engines to maintain its station at the focus and repositioning itself for new targets. The preferred site is the L2 point; a high circular orbit is also possible. Additional or replacement detectors equipped with ion/plasma engines are launched on much smaller rockets and rendez-vous with the telescope. We describe how such a telescope with an angular resolution of a few arcseconds could be fabricated. As an example, we consider a 7 m X 7 m aperture, 100 m focal length standard Kirkpatrick-Baez optic. It is segmented into several hundred modules of identical size. A co-aligned group of segments is equipped with a fiducial and a positioning system for alignment to a common focus in space. With subdivided reflector substrates made from light weight advanced composite materials the launch mass of the telescope spacecraft is within the capability of current vehicles.

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

The hard x-ray telescope (HXT) was selected for study as a possible new intermediate size mission for the early 21st century. Its principal attributes are: (1) multiwavelength observing with a system of focusing telescopes that collectively observe from the UV to over 1 MeV, (2) much higher sensitivity and much better angular resolution in the 10 - 100 keV band, and (3) higher sensitivity for detecting gamma ray lines of known energy in the 100 keV to 1 MeV band. The institutions collaborating in the study are: Smithsonian Astrophysical Observatory, Marshall Space Flight Center, Naval Research Laboratory, Goddard Space Flight Center, Argonne National Laboratory, Danish Space Research Institute, Osservatorio Astronomica di Brera (Merate), and Centre d'Etudes Spatiale des Rayonnements (Toulouse). This paper emphasizes the instrumentation development aspects of the concept study which is also of interest to other possible missions observing hard x rays. The instrumentation includes several grazing incidence double conical telescopes with multilayer coatings that focus up to 100 keV and a single Laue crystal telescope that functions to 1 MeV. The detectors which are relatively small thanks to focusing include CCDs, and germanium, and/or CdZnTe position sensitive arrays.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Wide field x-ray telescopes based upon the 'lobster eye' geometry can play an important role in future astronomical investigations. Our approach is based upon the geometry of Schmidt, 1975 in which a telescope is composed of two similar orthogonal stacks, each made from equally spaced identical flats that reflect on both faces. Its advantages are compatibility with large aperture and large field of view. Construction of a mirror reduces to two tasks, (1) mass producing thin, smooth, two sided flats and (2) securing them along two edges by a method that preserves their flatness. We are investigating both tasks in parallel. To address the first problem we are attempting to improve the flatness and reflectivity of an inexpensive, thin, commercial glass by replicating a smoother, flatter, gold coated surface on both faces. To address the second task, a small, 1D mirror assembly covering a 5 degree field of view was constructed from inexpensive, thin commercial glass that was coated on two sides with nickel. X-ray testing indicated that its resolution was consistent with theory and the approximately two arcminute deviation from flatness of the glass.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Multilayers as coatings for grazing incidence telescopes have the potential of effectively improving the performance of telescopes coated with high-Z elements. For broad-band high energy (+10 keV) applications the multilayers, called supermirrors, are ideal. In this presentation we present the preliminary results of a feasibility study of a multifocus Kirkpatrick-Baez telescope. We conclude that high quality multilayers can be performed on relevant thin large flat substrate with adequate uniformity, and that existing deposition chambers can produce the multilayers at a rate of 0.42 m2 per day, so that a coating reflectors for a 1200 cm2 aperture telescope would take 8.5 months. The only remaining unanswered question is whether these thin supermirror-coated reflected can be configured to a 2 - 3' tolerance.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Supermirrors are multilayer structures where the thickness of the layers down through the structure changes so that wide-band reflection occurs. The principles were developed in the mid-70s and have been used extensively for neutron optics. Absorption in the upper layers limits the attainable reflectivity for x rays. For hard x rays (>= 15 keV), the absorption, however, is low enough that it is possible to design supermirrors with 10 - 70% reflectivity in a band approximately equals 3 times the width of the total reflection regime. Supermirrors of W/Si and Ni/C have been successfully fabricated and characterized. The measured x-ray reflectivities are well accounted for by the standard dynamical theories of multilayer reflection. Hard x ray applications that could benefit from x-ray supermirror coatings include focusing and imaging instrumentation for astrophysics, collimating and focusing devices for synchrotron radiation, and particle filtering in plasma diagnostics.

By varying the thickness of the layers in a multilayer down through the structure, it is possible to produce wide-band reflectors. We report measurements and modeling of the reflectivity of Ni/C, Mo/Si and W/Si supermirrors, at energies ranging from 8 to 130 keV, and discuss the performance of two possible applications: a Kirkpatrick-Baez telescope, and a multiwavelength hard X-ray focusing reflector. The supermirrors perform as expected, and model-fits over the full range have been attempted with some success. We conclude that the supermirror coatings do indeed look very promising as hard x-ray optics for synchrotron applications, while some work on highly nested structures and supermirror coatings on very thin large substrates is necessary, before the feasibility of employing large-area supermirrors for hard X-ray astronomy is determined.

Traditional high-Z coated X-ray telescopes for the >= 1 keV range all have a loss of throughput with higher energies, owing to the inverse proportionality between the critical angle and energy. We have shown that this can, to some degree, be countered by employing multilayers on the outermost reflectors. A W/B4C multilayer has been fabricated and its 8 keV X-ray reflectivity measured and modeled, yielding an interface-roughness of 3.6 angstroms. This measurement and the resulting model-fit form the basis for computing the performance of `AXAF-S'-sized conical and Kirkpatrick-Baez telescopes. Depending on the specifics of the design, a factor 3 - 5 increased throughput was obtained in a narrow energy band, or a 30 - 100% increase in a wider-band. This throughput ia gained at the expense of the throughput at 2 - 4 keV, which is reduced by 20 - 30%.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

All focussing x-ray telescopes that have been in orbit (Einstein, EXOSAT, and ROSAT) or are currently being developed (e.g., ASTRO-D, SAX, AXAF, and XMM) are based upon the same type of optics, the Wolter Type I system or a conical approximation of it. With funding, weight, and volume now being severely limited, new investigations in x-ray astronomy will have to specialize on a particular study, e.g., wide field surveys, spectroscopy, broad band measurements, and should have significantly more capability than the current missions in that study. Several novel approaches to broad band and wide field optics have been described in the literature that may be able to satisfy certain specific objectives better than the Wolter I.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We present a concept of continuously graded multilayer structures for medium-sized x-ray telescopes which is based on several material combinations. We show that the theoretical reflectivity characteristics of these structures make them very advantageous when applied to high energy x-ray grazing incidence telescopes. We consider the performance of continuously graded Ni/C multilayers in a multi-focus, Kirkpatrick-Baez geometry and show a significant improvement when compared to standard coatings of gold. For a total length of 3.3 m, a total aperture of 48 cm by 48 cm, and 64 foci, we obtain an effective area of 250 cm2 at 60 keV and a FWHM field of view of 6 feet. We also show that a modular array of conical telescopes (conical approximation to a Wolter-I geometry), with the same length and aperture provides similar effective areas. Energy-dispersive x-ray reflectivity data (15 - 70 keV) is presented for the first continuously graded multilayer of this kind.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The development of glass microcapillary arrays by Kumakhov and co-workers in the Soviet Union suggests that it is possible to construct novel devices for concentrating and focussing X-ray beams. Hypothetical focussing concentrators made up of capillary arrays have been configured to operate over a broad range of X-ray energy and its characteristics have been studied with a Monte Carlo ray tracing code. These modeling results indicate that the concentrators would have significant effective area up to 100 keV while their dimensions are similar to conventional grazing incidence telescopes that operate in the soft X-ray band.

The paper surveys the Large Area Modular Array of Reflectors (LAMAR), the concept of which is based on meeting two major requirements in X-ray astronomy, large collecting area and moderately good or better angular resolution for avoiding source confusion and imaging source fields. It is shown that the LAMAR provides the same sensitivity and signal to noise in imaging as a single large telescope having the same area and angular resolution but is a great deal less costly to develop, construct, and integrate into a space mission. Attention is also given to the LAMAR modular nature which will allow for an evolutionary development from a modest size array on Spacelab to a Shuttle launched free flyer. Finally, consideration is given to manufacturing methods which show promise of making LAMAR meet the criteria of good angular resolution, relatively low cost, and capability for fast volume production.

The first of eight X-ray telescopes is under construction for the LAMAR experiment. Each consists of two orthogonal sets of nested confocal one-dimensional parabolic plates of gold-coated float glass, selected for flatness from commercial stock. Each is initially bent to a cylinder by bonding a thin, highly curved titanium sheet to its inactive surface. The final parabolic figure is produced by an automated system which includes seven diode arrays that detect a visible-light line image. Eight precise motorized linear translators operating under the control of a computer, tune the plate to the optimum figure. The plate is then fixed in position by epoxy bonds. The precision of the system is several arcsec, but the intrinsic flatness of the glass is expected to limit the half-power diameter (HPD) of the telescope to about 25 arcsec.

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.

An automated figure formation system for Kirkpatrick-Baez geometry grazing incidence X-ray mirrors is described. The system is based on an IBM PC/XT microcomputer and utilizes primarily commercially available equipment. The mirror assemblies currently being manufactured for the LAMAR experiment attain an angular resolution of ~30" (50% power diameter) on axis. The angular resolution is limited by the float glass used for the mirror plates, not the figure formation process.