We present an overview of currently available EUV multilayer coatings that can be used for the construction of solar physics instrumentation utilizing normal-incidence optics. We describe the performance of a variety of Si-based multilayers, including Si/B₄C and new Si/SiC films that provide improved performance in the wavelength range from 25 n 35 nm, as well as traditional Si/Mo multilayers, including broad-band coatings recently developed for the Solar-B/EIS instrument. We also outline prospects for operation at both longer and shorter EUV wavelengths, and also the potential of ultra-short-period multilayers that work near normal incidence in the soft X-ray region.

The measured efficiencies of two flight gratings and the reflectances of two flight mirrors developed for the Extreme-Ultraviolet Imaging Spectrometer (EIS) for the Japanese Solar-B mission are presented. Each optic has two sectors with Mo/Si multilayers that refelct the 17 - 21 nm and 25 - 29 nm wavebands at normal incidence. The efficiencies that were measured using monochromatic synchrotron radiation are in good agreement with the calculated efficiencies.

APEX is a proposed mission for a Small Explorer (SMEX) satellite. The instrument is a suite of 8 near-normal incidence EUV spectrometers and is the outgrowth of 17 years of research at NRL on multilayer coatings and holographic ion-etched diffraction gratings. A prototype spectrometer has been flown successfully on a sounding rocket. We have examined different multilayer and gratings designs and produced a configuration optimized for the proposed science. APEX will achieve a peak effective area of at least 30-50 cm² in the range 90-275 Å with resolution ~10,000, significant improvements on Chandra and EUVE.

The design of Mo/Si and Mo/Y multilayers as EUV polarizers is presented. The polarization performance of these multilayers was calculated based on their optical properties at around Brewster angles. The polarization results of a silicon photodiode that was coated with an interface-engineered Mo/Si multilayer are described. The sensitivity of this specially-coated photodiode and its polarization responses were determined from both reflectance and transmittance of the multilayer coating, using synchrotron radiation. The multilayer reflected 69.8% of s-polarized light and only 2.4% of p-polarized light, therefore transmitted about 0.2% s-polarized light and 8.4% p-polarized light at 13.5 nm to the underlying photodiode substrate. A polarization ratio based on transmittance values, (Tp-Ts)/(Tp+Ts), of 95% was achieved with sufficiently high sensitivity. This result demonstrates the usefulness of Mo/Si multilayer-coated photodiodes as future EUV polarimeters.

We have determined experimentally optical constants for eight thin film materials that can be used in hard X-ray multilayer coatings. Thin film samples of Ni_.97V_.03, Mo, W, Pt, C, B₄C, Si and SiC were deposited by magnetron sputtering onto superpolished optical flats. Optical constants were determined from fits to reflectance-vs-incidence angle measurements made using synchrotron radiation over the energy range E=35-180 keV. We have also measured the X-ray reflectance of a prototype W/SiC multilayer coating over the energy range E=35-100 keV, and we compare the measured reflectance with a calculation using the newly derived optical constants.

This paper outlines an in-depth study of the W/Si coated mirrors for the High Energy Focusing Telescope (HEFT). We present data taken at 8, 40 and 60 keV obtained at the Danish Space Research Institute and the European Synchrotron Radiation Facility in Grenoble. The set of samples were chosen to cover the parameter space of sample type, sample size and coating type. The investigation includes a study of the interfacial roughness across the sample surface, as substrates and later as coated, and an analysis of the roughness correlation in the W/Si coatings for N = 10 deposited bilayers. The powerlaw graded flight coating for the HEFT mirrors is studied for uniformity and scatter, as well as its performance at high energies.

The XEUS X-ray mission is currently being studied by ESA. It will be based on a huge (10 m of aperture diameter) grazing-incidence mirror unit with 50 m focal length, realized by a two separate satellites system, one dedicated to host the mirror module and the other for the detector. The current baseline foresees a single reflecting layer of Gold for the full set of 562 mirror shells of the XEUS telescope (296 shells of the first stage of the project, named XEUS I, with a maximum diameter of ~ 4 m, plus 266 shells of the second phase, named XEUS II, that will be activated after about 5 years). However, the use of multilayer mirrors instead of Au for XEUS-I (i.e. where the incidence angles of the mirror shells series are smaller) is an interesting alternative, already recently proposed by other authors, to extend the XEUS operative range in the hard X-ray region (up to 80 keV). In this work we applied a global optimization approach based on an “Iteraded Simplex Procedure” to optimize the sequence of bi-layers of depth-graded multilayer films, in order to get the best achievable response by the XEUS-I mirrors in the hard X-ray region. In addition, we theoretically evaluated the performances of the XEUS-II mirrors after the introduction of constant d-spacing multilayers with a thin (100 Å) overcoating of Carbon instead of Au. In this case the main advantage is given by an enhancement of the telescope effective area in the soft X-ray region (0.1-10 keV). The role of the Carbon top layer is to reduce the photoelectric absorption effect in the total-reflection regime, with an important improvement of the reflection efficiency with respect the usual mirrors based on high density materials like, e.g., Au, W, Ir and Pt.

Next Japanese X-ray mission after AstroE2 will be dedicated to the exploration of non-thermal phenomena in the Universe by the hard X-ray imaging, high resolution spectroscopy and broad band coverage. The objectives are the non-thermal X-ray components in cluster of galaxies and SNR, hidden AGN and their contribution to the cosmic X-ray background. Such non-thermal energy is considerable amount of the total energy in the Universe. Multilayer supermirror hard X-ray telescopes (50 cm diameter and 12 m focal length) will focus hard X-rays up to 60 keV or higher. Hybrid X-ray imaging system consisted of CCD cameras for soft X-ray imaging and a hard X-ray imaging detector will be placed at the focal points of four multilayer telescopes. A micro-calorimeter array detector is prepared for a soft X-ray telescope to perform imaging spectrometry (60 cm diameter and 8 m focal length). A soft gamma-ray detector will cover up to several hundred keV. It will provide extremely low background by imaging capability. This X-ray mission is now named "NeXT", which stands for "New X-ray Telescope mission" or "Non-thermal Energy eXpring Telescope mission." It will be launched in 2010 by an M-V rocket.

We report on the fabrication and performance of prototype optics for the Constellation-X hard X-ray telescope (HXT). The prototypes utilize segmented-glass optics. Multiple glass segments are combined to produce telescope shells. The shells are separated by and epoxied to graphite rods, and each layer of rods is precisely machined to match the required optical geometry of the corresponding glass shell. This error-compensating, monolithic assembly and alignment (EMAAL) procedure is novel. Two prototypes are described. The first used 10cm long thermally-slumped glass pieces produced by slumping into a concave mandrel with no subsequent replication. This prototype obtained 45" (2-bounce HPD). The second prototype was the first attempt to mount epoxy-replicated, thermally-slumped glass optics using EMAAL. The latter prototype demonstrated our ability to produce and mount glass shells whose figure and performance are faithful representations of the original replication mandrel. The average performance was 45", with the best replicated segment providing 33" (2-bounce HPD) performance, consistent with the ~30" measured with laser reflectometry and interferometry prior to mounting. Both these prototypes substantially exceeded the HXT requirement of 60".

Complete hard X-ray optics modules are currently being produced for the High Energy Focusing Telescope (HEFT), a balloon born mission that will observe a wide range of objects including young supernova remnants, active galactic nuclei, and galaxy clusters at energies between 20 and 70 keV. Large collecting areas are achieved by tightly nesting layers of grazing incidence mirrors in a conic approximation Wolter-I design. The segmented layers are made of thermally-formed glass substrates coated with depth-graded multilayer films for enhanced reflectivity. Our novel mounting technique involves constraining these mirror segments to successive layers of precisely machined graphite spacers. We report the production and calibration of the first HEFT optics module.

The Constellation-X mission, planned for launch in 2013, will feature an array of hard-x-ray telescopes (HXT) with a total collecting area of greater than 1500 cm² at 40 keV. Two technologies are currently being investigated for the optics of these telescopes including multilayer-coated Eletroformed-Nickel-Replicated (ENR) shells. The attraction of the ENR process is that the resulting full-shell optics are inherently stable and offer the prospect of better angular resolution which results in lower background and higher instrument sensitivity. The challenge for this process is to meet a relatively tight weight budget with a relatively dense material (ρ_nickel = 9 g/cm³.) To demonstrate the viability of the ENR process we are fabricating a prototype HXT mirror module to be tested against a competing segmented-glass-shell optic. The ENR prototype will consist of 5 shells of diameters from 150 mm to 280 mm with a length of 426 mm. To meet the stringent weight budget for Con-X, the shells will range in thickness from 100 microns to 150 microns. The innermost of these will be coated with Iridium, while the remainder will be coated with graded-dspaced W/Si multilayers. Mandrels for these shells are in the fabrication stage, the first test shells have been produced and are currently undergoing tests for figure and microroughness. A tentative date of June '04 has been set for the prototype X-ray testing at MSFC. Issues currently being addressed are the control of stresses in the multiplayer coating and ways of mitigating their effects on the figure of the necessarily thin shells. The fabrication, handling and mounting of these shells must be accomplished without inducing permanent figure distortions. A full status report on the prototype optic will be presented along with test results as available.

We have been developing the hard X-ray telescope for balloon borne experiment named InFOCμS. The first InFOCμS flight was carried out on July, 2001. In this flight, we obtained hard X-ray image of Cygnus X-1 above 20 keV. This is first observation with hard X-ray telescope using multilayers. In this mission, the platinum-carbon depth graded multilayers (supermirror) are used as X-ray reflectors combining multi nested thin foil optics to obtain enough efficiency in the hard X-ray region. They make us possible to obtain 40 cm³ effective area at 30 keV with 40 cm diameter of the telescope. After the first flight, the hard X-ray telescope was recovered without any damages, we measured performances of the telescope in synchrotron radiation facility SPring-8. We obtained the results, the half power diameter (HPD) is 2.4 arcmin and effective area is 38 cm² at 30 keV. These results show that no degradation of the performances of the hard X-ray telescope was observed in this measurement. Furthermore, we begin to fabricate new hard X-ray telescope for future InFOCμS flight. The design of the multilayer supermirrors are improved to widen the energy band. The performances of this telescope including effective area and spatial resolution are measured using synchrotron radiation facility SPring-8 and ISAS 30 m X-ray beam line. The measured effective area is significantly larger than the first telescope especially above 30 keV.

We have developed the electroformed-nickel replication process to enable us to fabricate light-weight, high-quality mirrors for the hard-x-ray region. Two projects currently utilizing this technology are the production of 240 mirror shells, of diameters ranging from 50 to 94 mm, for our HERO balloon payload, and 150- and 230-mm-diameter shells for a prototype Constellation-X hard-x-ray telescope module. The challenge for the former is to fabricate, mount, align and fly a large number of high-resolution mirrors within the constraints of a modest budget. For the latter, the challenge is to maintain high angular resolution despite weight-budget-driven mirror shell thicknesses (100 μm) which make the shells extremely sensitive to fabrication and handling stresses, and to ensure that the replication process does not degrade the ultra-smooth surface finish (~3Å) required for eventual multilayer coatings. We present a progress report on these two programs.

The Science Payload and Advance Concepts Office of the Science Directorate of the European Space Agency is responsible for developing and conducting a coherent and strategic technology program so as to ensure the feasibility of innovative advanced concepts for future science missions. These missions cover a wide range of disciplines ranging from astrophysics and fundamental physics to solar and planetary research, including exo-biology. The underpinning technology research and development is being conducted in collaboration with European industry and research institutes. The field of high energy photon optics for space applications has demonstrated substantial progress in the past decades, but continues to face very interesting challenges for the future missions. Low specific mass (mass per effective collecting area) is the driving parameter for most future mission designs, both for space based astrophysics observatories and planetary missions. New technologies have to be explored for future applications, simultaneously achieving good angular resolution and low mass. The next generation of high energy astrophysics missions will require the development of much improved optical systems for the x-ray range, and the introduction of focussing imaging systems in the gamma-ray regime. While adequate detection systems are already available, or in the process of refinement and optimization, the optical systems have posed the main hurdle in the design of new space missions. In this paper one potential alternative to the production of very lightweight X-ray optics, which is being investigated by ESA and its industrial partners, is discussed. First the applicability of the required optical design is addressed, followed by the currently ongoing work on the production facilities. Finally the impact of such optics on mission design is investigated based on the example of the X-ray Evolving Universe Spectroscopy mission XEUS. The cosmology mission XEUS requires very large effective area, 30 m² at 1 keV, X-ray optics with high angular resolution of below 5" with a goal of 2". This implies a large aperture for a single telescope system, which will necessarily require assembly or deployment in space, and which will be formed by basic mirror modules known a petals. The petals must remain compatible with compact ground handling and production tools and will require minimum modifications to existing calibration facilities. Such optics are also envisaged for applications such as astrophysics observatories placed in very deep orbits or in the field of planetary remote sensing. In the latter application there are even stronger mass constraints although a more relaxed angular resolution requirement (e.g. arc minutes compared to arc seconds). Such optics systems have as a single common feature a dramatically reduced mirror thickness and therefore mass.

For the next generation of X-ray observatories (CONSTELLATION-X and XEUS) a mass production of glass mirror segments is considered. The mirror substrates (SCHOTT D263 and SCHOTT BOROFLOAT 33) will be pre-shaped in a high temperature slumping process by use of precision forming mandrels. SCHOTT GLAS developed the glass ceramic material ZERODUR K20 to meet the requirements of these mandrels. The new material is a modification of the well-known ZERODUR. A heat driven transformation thereby changes the crystalline phase from high-quartz to keatite structure. The resulting ZERODUR K20 exhibits an increased stability at high temperatures of up to 850°C and a low thermal expansion coefficient (CTE) of approximately 20•10^-7 K^-1 (20°-700°C). Numerical simulations of the slumping process based on experimental parameters of Zerodur K20 and the mirror substrate materials are presented.

Constellation-X is NASA’s next major X-ray observatory, planned to be launched in 2012-2013. Each of the four identical satellites contains a large diameter (1.6 m) spectroscopic X-ray telescope (SXT). The mirror assembly consists of many densely nested Wolter type 1 mirrors with segment angles of 30 and 60 degrees. The mirror segments will be made of thin, accurately shaped glass substrates onto which the reflective mirror surface is replicated from high precision, super polished mandrels. In this paper we report about design, fabrication, metrology and analyses of the optical performance of three prototype mandrels to be used by NASA in the constellation-X mirror development program. The prototype mandrels are characterized by the following features: Material: Zerodur; overall length: 1100 mm; segment angles: > 30°; radius at paraboloid-hyperboloid intersection: 800 mm, 600 mm and 500 mm; focal length: 10 000 mm.

The Constellation-X observatory is planned to have four identical satellites, each of which carries, among other instruments, a Spectroscopic X-ray Telescope (SXT). The SXT has a 10m focal length and 1.6 m diameter aperture. It has a total effective X-ray collection area of ~7,500 cm² at 1 keV. Mission science requirements call for an angular resolution of 15" half-power diameter (HPD) at the observatory level. Combining the large collection area requirement, the angular resolution requirement, and a mass requirement, we are faced with an unprecedented task of fabricating X-ray mirror segments with an areal density of only 1 kg/m² which is typically called gossamer optics. We have adopted at two-step process for fabricating the mirror segments: (1) first slump a flat sheet of glass onto a forming mandrel to create a substrate, and then (2) epoxy-replicate the substrate off a precision replication mandrel to eliminate any defects or errors on its surface. As of the writing of this paper in late August 2003, we have demonstrated a process for reliably making excellent substrates. Best mirror segments fabricated so far, if aligned and mounted without error, have an angular resolution in the vicinity of 20" HPD, close to, but not quite, meeting requirements. We expect that in the next year, when forming mandrels that meet requirements are procured, we will be able to fabricate mirror segments that actually meet and even possibly exceed the SXT requirements. In this paper, we report on the baseline mirror fabrication method and the status of its development as of August 2003.

The XEUS mission (X-ray Evolving-Universe Spectroscopy Mission) is a future ESA project currently under study. With a mirror collecting area of up to 30 m² @ 1 keV and 3 m² @ 8 keV it will outperform the x-ray space observatories like XMM-Newton. In fact it will have a source flux sensitivity and angular resolution respectively 250 times and 7.5 times better if compared to that mission. This huge collecting area is obtained with a 10 m diameter telescope of 50 m focal length. It is foreseen that the whole telescope will be formed by two free flying satellites, one for the mirror assembly and the other for the detectors. The two satellites will be kept aligned by an active tracking/orbit control system. The angular resolution of the optics is set to 5 arcsec with a goal of 2 arcsec. Of course the requirement of high resolution and large diameter of the optics create new technological problems which have to be overcome. First of all the impossibility to create closed Wolter I shells (due to the large diameter) means that the optics will be assembled using rectangular segments of ~1 m x ~0.5 m size. A set of these segments will form a petal. The petals will be assembled to form the whole mirror assembly. Another difficulty arises from the fact that the current design foresees a mass/geometric-area ratio of 0.08 kg/cm², which is very small and much lower compared with XMM-Newton. Hence the use of materials that can offer both low weight and high stiffness is mandatory. The impossibility to have a thermal control for the huge area of the optics means also that the mirrors have to operate at temperatures between -30 and -40°C. This requirement excludes the epoxy-replication method as option for their manufacturing (CTE mismatch between resin and substrate). Considering all these constrains a possible solution for the realization of the XEUS mirrors has been found that foresees the use of glass or ceramics materials. In this paper we will describe an investigation currently on-going aimed at the development of a procedure to produce large mirror segments from thin Borofloat glass and the preliminary results obtained, that corroborate the viability of the proposed approach. A previous article has introduced the basic ideas and concepts behind this investigation.

The Constellation X-ray Observatory consists of four identical spacecraft, each carrying a complement of high sensitivity X-ray instrumentation. At the heart of each is the grazing incidence mirror of the Spectroscopy X-ray Telescope (SXT). This mirror has a diameter of 1.6 m, a focal length of 10 m, mass not exceeding ~650 kg. The required angular resolution is 15 arc seconds and the effective area at 1 keV must exceed 7,500 cm². Achieving these performance requirements in a cost effective way within the allocated mass is accomplished via a modular design, incorporating lightweight, multiply-nested, segmented Wolter Type I X-ray mirrors. The reflecting elements are composed of thin, thermally formed glass sheets, with epoxy-replicated X-ray reflecting surfaces. Co-alignment of groups of reflectors to the required sub-micron accuracy is assisted by precision silicon microstructures. Optical alignment incorporates the Centroid Detector Assembly (CDA) originally developed for aligning the Chandra mirror. In this talk we present an overview of recent progress in the SXT technology development program. Recent efforts have concentrated on producing an engineering unit that demonstrates all the key fabrication and alignment processes, and meets the angular resolution performance goal. Additionally, we describe the initial steps toward flight mirror production, anticipating a Constellation-X launch early in the next decade.

We present the metrology requirements and metrology implementation necessary to prove out the mirror technology for the Constellation-X (C-X) soft x-ray telescope (SXT). This segmented, 1.6m diameter highly nested Wolter-1 telescope presents many metrology and alignment challenges. A variety of contact and non-contact optical shape measurement, profiling and interferometric methods are combined to test the forming mandrels, some of the replication mandrels, the formed glass substrates before replication and the replicated mirror segments. The mirror segments are tested both stand-alone and in-situ in mirror assemblies. Some of these methods have not been used on prior x-ray telescopes and some are feasible only because of the segmented approach used on the SXT. Methods to be discussed include axial interferometric profiling, azimuthal circularity profiling, midfrequency error profiling, and axial roughness profiling. The most critical measurement is axial profiling, and we compare the method in use to previous methods such as the long trace profilometer (LTP). A companion paper discusses the method of non-contact 3D profiling using a laser sensor and distance measuring interferometers.

We are reporting our progress in the measurements of thin glass optics under development for the soft X-ray telescope for the Constellation-X space observatory. We are using a Non-Contact laser probe (which uses triangulation techniques to measure displacement) to determine the surface shape of our ultra-lightweight mirrors. If this technique meets technical specifications we will for the first time have mapped the 3 dimensional surfaces of ultra-lightweight optics. As a secondary project, we are also automating this entire process which will give us better repeatability.

We are developing grazing incidence x-ray optics for a balloon-borne hard-x-ray telescope (HERO). The HERO mirror shells are fabricated using electroform-nickel replication off super-polished cylindrical mandrels. One of the sources for mirror resolution error is departure of the shell figure from prescription. We have modified a Vertical-scan Long Trace Profilometer (VLTP) in order to measure the figure of the inner surface of the HERO mirror shells for diameters as small as 74 mm. Metrology of the figure, the microroughness, tilt angle, the circularity for the shell mirrors and the mandrels, as well as alignment procedures are discussed. Comparison of metrology of the mandrel and the shells is presented together with results from x-ray tests.

This paper describes optical metrology and an alignment/integration sequence which has the potential to secure sub arc second accuracy for a single focus Wolter type I telescope like XEUS. The same basic principle could be used for any grazing incidence Wolter type I design in which the aperture is divided into sectors and the Wolter surfaces are manufactured as sector plates rather than continuous surfaces of revolution. If such a scheme could be implemented then the performance of XEUS would be limited by the quality of the mirror plates and the plate mounting rather than the integration and alignment procedure.

The Constellation-X SXT mirrors and housings continue to evolve toward a flight-like design. Our second-generation alignment housing, the Optical Alignment Pathfinder 2 (OAP2), is a monolithic titanium structure that is nested inside the OAP1 alignment jig, described in a previous paper (J. Hair, et. al., SPIE 2002). In order to perform x-ray tests in a configuration where the optical axis is horizontal, and continue to develop more flight-like structures, we needed to design a strong, but lightweight housing that would impart minimal deformations on the thin segmented mirrors when it is rotated from the vertical orientation used for optical alignment to the horizontal orientation that is used for x-ray testing. This paper will focus on the design of the OAP2 housing, and the assembly and alignment of the optics within the OAP1 plus OAP2 combination using the Centroid Detector Assembly (CDA). The CDA is an optical alignment tool that was successfully used for the HRMA alignment on the Chandra X-ray Observatory. In addition, since the glass we are using is so thin and flexible, we will present the response of the optical alignment quality of a Wolter-I segment to known deformations introduced in by the OAP1 alignment housing.

Cosmic soft X-ray spectroscopy exploits principal transitions of astrophysically abundant elements to infer physical properties of objects in the sky. Most of these transitions, however, fall well below 2 keV, or 6 Angstroms. Consquently, grating spectrometers offer the current, best means by which to analyze soft X-rays from such sources, where throughput and resolving power must be maximized together. We describe grating spectrometer design candidates for the future mission Constellation-X, and how the grating array on board (~1000 gratings in a 1600mm diameter, each for 4 instruments) may be implemented. Grating fabrication and grating alignment approaches require special consideration (over the XMM-Newton RGS experience), because of grating replication fidelity and instrument mass constraints.

Both classical (in-plane) and conical (off-plane) grating configurations can be used in the spectrometer being developed for the Spectroscopy X-ray Telescope (SXT), which is assigned for the Constellation-X mission. Rigorous absolute efficiency calculations of gold-coated diffraction gratings with ideal triangular, trapezoidal, and polygonal profiles have been carried out for both possible spectrometer mountings by the PCGrate-SX program based on a modified integral method, with due account of random roughness. Optimum grating parameters and spectrometer configuration providing maximum theoretical efficiency were determined. Rigorous calculations performed with optimization showed that blazed grating absolute efficiency for the in-plane configuration similar to that employed in the XMM-Newton X-ray telescope cannot exceed 0.2-0.3 at the maxima in the minus first diffraction order within the relevant range of grazing angles, frequencies, and blaze angles. By contrast, using a grazing off-plane mounting permits one to compute gratings with a few times higher theoretical absolute efficiency in first diffraction orders, both at the maxima and on the average, for much higher grating frequencies and blazing angles. Unlike the classical mount, conical diffraction gives rise to noticeable polarization effects and Rayleigh anomalies in TM polarization. In view of the possibility of fabricating almost ideal triangular grooves by anisotropic etching of smooth graze-cut (111) silicon wafers by interference lithography and of compensating aberrations by properly modifying the frequency and/or grating groove curvature, the off-plane grating configuration may turn out preferable, particularly if a high spectral resolving power can be reached. A comparison with efficiency calculations and measurements is presented.

The Reflection Grating Spectrometer (RGS) on Constellation-X will require thousands of large gratings with very exacting tolerances. Two types of grating geometries have been proposed. In-plane gratings have low ruling densities (~500 l/mm) and very tight flatness and assembly tolerances. Off-plane gratings require much higher ruling densities (~5000 l/mm), but have somewhat relaxed flatness and assembly tolerances and offer the potential of higher resolution and efficiency. The trade-offs between these designs are complex and are currently being studied. To help address critical issues of manufacturability we are developing a number of novel technologies for shaping, assembling, and patterning large-area reflection gratings that are amenable to low-cost manufacturing. In particular, we report results of improved methods for patterning the sawtooth grating lines that are required for efficient blazing, including the use of anisotropic etching of specially-cut silicon wafers to pattern atomically smooth grating facets. We also report on the results of using nanoimprint lithography as a potential means for replicating sawtooth grating masters. Our Nanoruler scanning beam interference lithography tool allows us to pattern large area gratings up to 300 mm in diameter. We also report on developments in grating assembly technology utilizing lithographically patterned and micromachined silicon metrology structures ("microcombs") that have achieved submicron assembly repeatability.

The Max-Planck-Institut fuer extraterrestrische Physik (MPE) in Garching, Germany, operates the large X-ray beam line facility PANTER for testing astronomical systems. At PANTER a number of telescopes like EXOSAT, ROSAT, SAX, JET-X, ABRIXAS, XMM and SWIFT operating in the soft energy range (0.02 - 15 keV) have been successfully calibrated. In the present paper we report on an important upgrade recently implemented that enables the calibration of hard X-ray optics (from 15 up to 50 keV). Currently hard X-ray optics based on single and multilayer coating are being developed for several future X-ray missions. The hard X-ray calibrations at PANTER are carried out by a high energy source based on an electron gun and several anodes, able to cover the energy range from 4.5 up to 50 keV. It provides fluxes up to 10⁴ counts/sec/cm² at the instrument chamber with a stability better than 1%. As detector a pn-CCD camera operating between 0.2 and 50 keV and a collecting area of 36 cm² is used. Taking into account the high energy resolution of the CCD (145 eV at 6 keV), a very easy way to operate the facility in hard X-ray is in energy-dispersive mode (i.e. with a broad-band beam). A double crystal monochromator is also available providing energies up to 20 keV. In this paper we present the first results obtained by using PANTER for hard X-ray characterizations, performed on prototype multilayer optics developed by the Osservatorio Astronomico di Brera (OAB), Milano, Italy, and the Harvard-Smithsonian Center for Astrophysics (CfA), Cambridge, MA, USA.

Astro-E2, to be launched in early 2005, will carry five X-ray Telescopes (XRT). The design of the XRT is the same as the previous original mission Astro-E, that is a conical approximation of Wolter Type-I optics, where about 170 thin-foil reflectors are nested confocally. Some modifications from Astro-E are adopted within the severe constraints due to the policy of "re-build" instruments. One of the major changes is the addition of pre-collimators for the stray light protection. Several modifications on the fabrication processes are also made. The replication glass mandrels are screened carefully, which is expected to reduce the figure error of replicated reflectors. We thus expect better performance than Astro-E especially in imaging capability. In order to qualify the performance of the Astro-E2 XRT, we have started ground calibration program of XRT at 30 meter X-ray beam facility of the Institute of Space and Astronautical Science (ISAS). We have found positive improvements on the telescope performance from the Astro-E, which probably arise from the applied modifications. The on-axis half-power diameter (HPD) has been evaluated to be 1.6-1.7 arcmin, which is improved from the Astro-E (2.0 ~ 2.1 arcmin HPD). The on-axis effective areas of quadrants are larger than the average of Astro-E by about 5%. The on-axis effective areas of the XRT for X-ray Imaging Spectrometers (XIS) are approximately 460, 340, 260, and 190 cm² at energies of 1.49, 4.51, 8.04, and 9.44 keV, respectively. The present paper describes the recent results of the performance of the first flight assembly of the Astro-E2 XRT.

As NASA’s next facility-class x-ray mission, Constellation X will provide high-throughput, high-resolution spectroscopy for addressing fundamental astrophysical and cosmological questions. Key to the Constellation-X mission is the development of lightweight grazing-incidence optics for its Spectroscopy X-ray Telescopes (SXT) and for its Hard X-ray Telescopes (HXT). In preparation for x-ray testing Constellation-X SXT and HXT development and demonstration optics, Marshall Space Flight Center (MSFC) is upgrading its 100-m x-ray test facility, including development of a five degree-of-freedom (5-DoF) mount for translating and tilting test articles within the facility’s large vacuum chamber. To support development of alignment and assembly procedures for lightweight x-ray optics, Goddard Space Flight Center (GSFC) has prepared the Optical Alignment Pathfinder Two (OAP2), which will serve as a surrogate optic for developing and rehearsing x-ray test procedures. In order to minimize thermal distortion of the mirrors during x-ray testing, the Harvard-Smithsonian Center for Astrophysics (CfA) has designed and implemented a thermal control and monitoring system for the OAP2. CfA has also built an aperture wheel for masking and sub-aperture sampling of the OAP2 to aid in characterizing x-ray performance of test optics.

The Constellation-X mission is a follow-on to the current Chandra and XMM missions. It will place in orbit an array of four X-ray telescopes that will work in unison, having a substantial increase in effective area, energy resolution, and energy bandpass over current missions. To accomplish these ambitious increases new optics technologies must be exploited. The primary instrument for the mission is the Spectroscopy X-Ray Telescope (SXT), which covers the 0.21 to 10 keV band with a combination of two x-ray detectors: a reflection grating spectrometer with CCD readout and a micro-calorimeter. Mission requirements are an effective area of 15,000 cm² near 1 keV and a 15 arc-sec (HPD) image resolution with a goal of 5 arc-sec. The Constellation-X SXT uses a segmented design with lightweight replicated optics. A technology development program is being pursued with the intent of demonstrating technical readiness prior to the program new start. Key elements of the program include the replication of the optical elements, assembly and alignment of the optics into a complete mirror assembly and demonstration of production techniques needed for fabrication of multiple units. These elements will be demonstrated in a series of engineering development and prototype optical assemblies which are increasingly flight-like. In this paper we present an image angular resolution error budgets for the SXT and for the Optical Assembly Pathfinder #2 (OAP2), the first of engineering development units intended to be tested in x-rays. We describe OAP2 image error sources and performance analyses made to assess error sensitivities. Finally we present an overall prediction of as-tested imaging performance in the x-ray test facility.

It is well known that the Wolter I design for focusing X-ray telescopes provides perfect on-axis images, while, despite the absence of spherical aberration, the off-axis angular resolution rapidly degrades because of coma, field curvature and astigmatism. However, more general mirror designs than Wolter's exist in which primary and secondary mirror profiles can be described by polynomial equations. These power series solutions are particularly well indicated to be optimized, in order to achieve high imaging performances even at large off-axis incidence angles, despite a small degradation of the on-axis response. The concept, derived from the Ritchey-Chretien telescope widely used in optical astronomy, has already been experimentally proven for X-ray astronomical applications at the Brera Astronomical Observatory (Italy), in the context of the feasibility study of the Wide Field X-ray Telescope mission. Here we present a new design (including a model for slope errors and mechanical tolerances) for a X-ray telescope of medium-size class assuming monolithic mirror shells made of glass, optimized to have a Half Energy Width better than 5 arcsec over a 30 arcmin field of view (radius) and an effective area almost twice that one of Chandra. The use of polynomial mirrors seems extremely well suited also for the case of the XEUS optics. Indeed, the small aspect-ratio between the large focal length of the XEUS telescope (50 m) and the total mirror height (1 m) makes it very favorable to diminish the aberration effects due to the field curvature. With the assumption of mirror shells with polynomial profile it would be possible to achieve for XEUS an imaging response almost constant up to a field of view of 20 arcmin in radius.

We study grazing incidence equal-curvature telescope designs for the Constellation-X mission. These telescopes have nearly spherical axial surfaces. The telescopes are designed so that the axial curvature is the same on the primary and secondary. The optical performance of these telescopes is for all practical purposes identical to the equivalent Wolter telescopes.

Astro-E2 XRTs adopt Wolter Type-I optics and have nested thin foil structure to enhance their throughput. But this structure allows stray X-rays to come from the sky outside of the XRT field of view. Stray lights contaminate focal plane images, especially in the case of extended source observations. We intend to mount pre-collimators on top of the ASTRO-E2 XRTs to intercept stray lights. According to the success for the engineering model pre-collimator to protect the stray lights efficiently, we proceeded to product flight model pre-collimators. Some improements are made for the flight model (FM) pre-collimator: the introduction of heat forming to make slats accurate cylindrical shape, the change of the groove shape of alignment plates and the change of the housing design. We also established the method of pre-collimator mounting. In X-ray measurements, stray light images and the flux of each stray component at any off-axis angles are measured with/without FM pre-collimator. The secondary only reflection component is reduced down to 3% at a larger off-axis angle than 30', and the backside reflection component becomes more remarkable. On the other hand, X-ray measurement of the effective area at on-axis with/without FM pre-collimator verifies that pre-collimator does not interfere the telescope aperture. In addition, the decrease of XRT field of view is ≤8%, which is the same as the ray-tracing simulations.

X-Ray Spectrometer (XRS) is the microcalorimeter onboard the X-ray astronomy satellite Astro-E2 which is scheduled to be launched early in 2005. For the XRS to achieve its best energy resolution of 6 eV at 6 keV, X-ray intensity should be limited up to several c s^-1 pixel^-1. The filter wheel (FW) is the instrument to reduce incident X-ray intensity on the XRS using extinction filters. The FW consists of a stepping motor, extinction filters, and a filter disk which has six mounting positions for the extinction filters. Among the six mounting points, two are used for Neutral Density (ND) filters, another two are for Beryllium (Be) filters, and the other two are remained open. The biggest modification from Astro-E is that we attach radioisotopes of ⁵⁵Fe and ⁴¹Ca on the filter disk, which illuminate the XRS pixels to monitor the gain in orbit. We present here the mechanical design of the FW especially on improvements from Astro-E, and the results of our calibration measurements on X-ray transmission of the extinction filters.

We measured optical and soft X-ray transmission of Optical Blocking Filters (OBFs) for Charge Coupled Device (CCD) cameras, which will be launched as focal plane detectors of X-ray telescopes onboard the Japanese 5th X-ray astronomical satellite, Astro-E 2. The filters were made from polyimide coated with Al. The X-ray absorption fine structures (XAFSs) at the K edges of C, N, O and K and L edges of Al were measured. The depth of the absorption edge of O was deep, compared to the other elements of polyimide. This is evidence of the oxidation of Al. The optical transmission is roughly less than 10^-6 except for a peak around the wave length of 550 nm. Long term change of the soft X-ray transmission was measured. No significant change of the thickness of the oxidation layer was found during half year.

We are developing the new type of X-ray telescope with short focal length for small satellite to perform the fine spectroscopic study of diffus soft X-rays with very low surface brightness. Point of the design of such system is to use four-stage reflection to reduce focal length. For this purpose, techniques developed for the fabrication of high throughput X-ray telescope for ASTRO-E/E2 satellite can be applied. Though the energy range is restricted below 1 keV, a combination with X-ray micro-calorimeter can provide us powerful tool for the study such as the detection of warm-hot intergalactic medium with the temperature of several millions degree, which should exist in the peripheral region around clusters of galaxies. We will report on the the design of such system, results of performance estimation by ray tracing program.

The wide field Lobster Eye telescopes are expected to play an important role in future X-ray astrophysics missions and analyses. The advanced prototypes of Lobster Eye optics modules of various sizes and various arrangements confirm the justification of space applications of theses innovative devices. Recently, both very small LE Schmidt prototypes (3x3 mm based on 0.03 mm foils spaced at 0.07 mm) as well as large (300 x 300 mm based on 0.75 mm foils spaced at 10.8 mm) have been designed, developed and tested. Advanced technologies for additional surface layers have been also investigated. The extended computer simulations confirm the high performance and scientific justification of the space born Lobster Eye telescope experiment. Emphasis was given on the alternative approach for the future ESA projects. We describe and discuss here the recent progress in the design, simulations, development and tests of advanced multifoil X-ray telescope prototypes.

Imaging at hard X-ray energies (~10-600 keV) over very large fields of view (~60° per telescope) is required to conduct a high sensitivity all-sky and all-time survey for black holes. The proposed Energetic X-ray Imaging Survey Telescope (EXIST) could achieve the high sensitivity required for the mission science objectives by scanning an array of wide-field coded aperture telescopes with aperture mask holes radially aligned to minimize auto-collimation by the thick (~7mm) masks required for high energy imaging. Simulation results from a preliminary design study are reported which quantify the improvement in off-axis imaging sensitivity vs. the conventional case with mask holes all perpendicular to the mask. Such masks can be readily constructed from a stacked laminate of thin (1mm) laser-etched W sheets. An even more dramatic increase in coded aperture imaging sensitivity, and dynamic range, for a realistic telescope and imaging detector with typical systematic errors can be achieved by continuously scanning the field of view of the telescope over the source region to be imaged. Simulation results are reported for detectors with systematic errors 1-10%, randomly distributed but unknown in each detector pixel. For the simplified case of a 1-D coded aperture telescope scanning along its pattern, the systematics are removed identically. Results are also presented for the 2-D case with both 1-D and partial 2-D scanning which demonstrate the feasibility of a coded aperture scanning telescope with systematic errors achieving nearly Poisson-limited sensitivity for signal/background ratios S/B ~ 10^-4, in constrast to limits typically ~10-100X worse that have been actually achieved by pointed or dithered coded aperture telescopes flown (or proposed) previously.

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 MicroArcsecond Imaging Mission (MAXIM) will resolve the event horizons of black holes with 0.1 microarcsecond imaging in the X-ray bandpass. In the NASA "Beyond Einstein" roadmap, MAXIM takes it place as the "Black hole Imager." In this paper, we will outline the scientific goals for this mission. We will describe the current state of the technology -- including a discussion of several laboratory demonstrations of X-ray interferometry. We will describe some engineering studies we have performed over the past two years.

The x-ray band of the spectrum is the natural place to perform super-high resolution imaging of astronomical objects. Because x-ray sources can have very intense surface brightness and interferometers can be made with very short baselines, x-ray interferometry has great potential. We will discuss MAXIM, the Micro-Arcsecond X-ray Imaging Mission and, in particular, MAXIM Pathfinder, a coordinated pair of x-ray astronomy missions designed to exploit the potential of x-ray interferometry. We will show how it is possible to achieve huge gains in resolution using today's technology. The Pathfinder mission will achieve resolution of 100 micro-arcseconds and will image the coronae of the nearby stars. MAXIM, with a design specification of 0.1 micro-arcseconds, has the goal of imaging the event horizons of massive black holes. We will explain the architecture of a possible Pathfinder mission and describe the activities NASA is supporting in the area of x-ray interferometry.

This paper discusses X-ray interferometer designs with milli-arcsecond resolution. The goal of this work was to derive interferometer designs that can be built and operated within the budget of a NASA mission. The current interferometer mission designs we propose use separate spacecraft for the optics and detector. Applying design techniques that desensitize the optical performance of the interferometer to spacecraft tip-tilt, and de-center errors was the goal of this work. An interferometer design will be presented with milli-arcsecond resolution. The requirements on relative motion between the spacecraft carrying the interferometer optics and the detector are discussed. Optical performance predictions will be shown.

Phase Fresnel lenses have the same imaging properties as zone plates, but with the possibility of concentrating all of the incident power into the primary focus, increasing the maximum theoretical efficiency from 11% to close to 100%. For X-rays, and in particular for gamma-rays, large, diffraction-limited phase Fresnel lenses can be made relatively easily. The focal length is very long - for example up to a million kms. However, the correspondingly high 'plate-scale' of the image means that the ultra-high (sub-micro-arc-second) angular resolution possible with a diffraction limited gamma-ray lens a few meters in diameter can be exploited with detectors having mm spatial resolution. The potential of such systems for ultra-high angular resolution astronomy, and for attaining the sensitivity improvements desperately needed for certain other studies, are reviewed and the advantages and disadvantages vis-a-vis alternative approaches are discussed. We report on reduced-scale 'proof-of-principle tests' which are planned and on mission studies of the implementation of a Fresnel telescope on a space mission with lens and detector on two spacecraft separated by one million km. Such a telescope would be capable of resolving emission from super-massive black holes on the scale of their event horizons and would have the sensitivity necessary to detect gamma-ray lines from distant supernovae. We show how diffractive/refractive optics leads to a continuum of possible system designs between filled aperture lenses and wideband interferometric arrays.

CLAIRE is a balloon-borne experiment dedicated to validating the concept of a diffraction gamma-ray lens. This new concept for high energy telescopes is very promising and could significantly increase sensitivity and angular resolution in nuclear astrophysics. CLAIRE's lens consists of 556 Ge-Si crystals, focusing 170 keV gamma-ray photons onto a 3x3 matrix of HPGe detectors, each detector element being only 1.4x1.4x4 cm³. On June 14 2001, CLAIRE was launched by the French Space Agency (CNES)from its balloon base at Gap in the French Alps and was recovered near the Atlantic ocean (500 km to the west) after about 5 hours at float altitude. Pointing accuracy and gondola stabilization allowed us to select 1^h12' of "good time intervals" for the data analysis. During this time, 33 diffracted photons have been detected leading to a 3σ detection of the source. Additional measurements made on a ground based 205 meters long test range are also presented. The results of this latter experiment confirm those of the stratospheric flight.

The mission concept MAX is a space borne crystal diffraction telescope, featuring a broad-band Laue lens optimized for the observation of compact sources in two wide energy bands of high astrophysical relevance. For the first time in this domain, gamma-rays will be focused from the large collecting area of a crystal diffraction lens onto a very small detector volume. As a consequence, the background noise is extremely low, making possible unprecedented sensitivities. The primary scientific objective of MAX is the study of type Ia supernovae by measuring intensities, shifts and shapes of their nuclear gamma-ray lines. When finally understood and calibrated, these profoundly radioactive events will be crucial in measuring the size, shape, and age of the Universe. Observing the radioactivities from a substantial sample of supernovae and novae will significantly improve our understanding of explosive nucleosynthesis. Moreover, the sensitive gamma-ray line spectroscopy performed with MAX is expected to clarify the nature of galactic microquasars (e⁺e^- annihilation radiation from the jets), neutrons stars and pulsars, X-ray Binaries, AGN, solar flares and, last but not least, gamma-ray afterglow from gamma-burst counterparts.

High groove density reflection gratings placed at grazing incidence in the extreme off-plane mount offer increased performance over conventional in-plane mounts in the x-ray. We present initial off-plane efficiency test results from the grating evaluation facility at the University of Colorado. The test gratings are holographically ruled, ion-etched gratings with radial groove profiles that were developed and fabricated by Jobin-Yvon Inc.

The University of Colorado maintains a grating evaluation facility to characterize optics from the far ultraviolet to the X-ray. The newest addition to this facility is a novel X-ray monochromator. Light is generated by a Manson electron impact X-ray source and passes through a monochromator which incorporates a grating in the off-plane mount at grazing incidence followed by an aluminum filter. From here, the light enters another vacuum chamber to illuminate the test grating, which disperses light onto a resistive anode MCP. This monochromator is characterized utilizing a variety of source anodes and voltages. Preliminary results from a high density test grating, also in the off-plane mount, display that this system is a highly effective tool for determining grating efficiencies.

High-resolution transmission electron microscopy (HRTEM) studies were performed on Pt/C multilayers fabricated for x-ray mirror optics. The multilayers with d-spacing of about 4 nm were deposited either by dc-magnetron sputtering or by ion-beam sputtering on commercially available Si wafer substrates. Atomic resolution TEM observations and selected area electron diffraction (SAED) of cross-sections of multilayers were made by using several TEM apparatus including an ultra-high-voltage TEM with theoretical point resolution of 0.10 nm. The HRTEM and SAED studies showed that the multilayer consisted of amorphous C layers and polycrystalline Pt layers having a texture with the Pt <111> axes oriented normal to the interface. The Pt grain size perpendicular to the layers was of about the layer thickness, while the grain size along the layers varied in a range up to 10 nm. Detailed analysis of the HRTEM images indicated that the interface of the multilayer was basically defined as surface of the Pt crystal grains, and the interface roughness originated in an arrangement of the grains. Interface broadening observed in the image was primarily attributed to the averaging of the roughness due to Pt grains.

SIMBOL-X is a hard X-ray mission, operating in the 0.5-70 keV range, which is proposed by a consortium of European laboratories for a launch around 2010. Relying on two spacecraft in a formation flying configuration, SIMBOL-X uses a 30 m focal length X-ray mirror to achieve an unprecedented angular resolution (30 arcsec HEW) and sensitivity (100 times better than INTEGRAL below 50 keV) in the hard X-ray range. SIMBOL-X will allow to elucidate fundamental questions in high energy astrophysics, such as the physics of accretion onto Black Holes, of acceleration in quasar jets and in supernovae remnants, or the nature of the hard X-ray diffuse emission. The scientific objectives and the baseline concepts of the mission and hardware design are presented.

A number of hard X-Ray (10 - 100 KeV) astronomical missions of near future will make use of multilayer-coated focusing mirrors. The technology based on Nickel electroformed replication is suitable for the multilayer optics realization, since multi-modular telescopes are foreseen. For example, for the Constellation-X mission there is the need of realizing up to 14 identical modules (12 flight modules plus two spares) which can be replicated by the same series of mandrels. The Ni replication approach is derived from the method already successfully used for making the Au coated soft X-ray mirrors with good imaging performances of the missions BeppoSAX, XMM-Newton and Swift. In the technological extension of the process to the multilayer optics fabrication, it would be convenient to overcoat the external surface of mandrels (normally in Kanigen) with a layer made of a very hard material. This would help to maintain the very low roughness level requested by the application (typically less than a couple of Angstroms for a 1 micrometer scan length with AFM) also after many replications and successive cleaning of the mandrel. Good material candidate are at this regard TiN and SiC, both characterized by a very high hardness. We have proven that flat prototypes with TiN and SiC overcoating can be superpolished at a level comparable to the traditional electroless Nickel coating. In this paper we will present a characterization by topographic measurement (AFM and WYKO) and by X-Ray scattering of two of these samples.