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Adjustable X-ray optics is the technology under study by SAO and PSU for the realization of the proposed X-ray telescope Lynx. The technology is based on thin films of lead-zirconate-titanate (PZT) deposited on the back of thermally formed thin substrates, and represents a potential solution to the challenging trade-off between high-surface quality and low mass, that limits the performance of current generation of X-ray telescopes. The technology enables the correction of mirror fabrication figure, mounting induced distortions, and on-orbit correction for variations in the mirror thermal environment. We describe the current state of development, presenting updated test data, anticipation of performances and expectations.

The combination of the hot slumping and the Ion Beam Figuring (IBF) technologies can be a very competitive solution for the realization of x-ray optics with excellent imaging capabilities and high throughput. While very thin mirrors segments can be realized by slumping with residual figure errors below few hundreds of nanometres, a non-contact and deterministic process (dependent on dwell time), like IBF, is a very effective post facto correction, as it avoids all the problems due to the handling and the supporting system. In the last years, the two processes were proven compatible with very thin sheet of Eagle XG glasses (0.4 mm thickness). Nevertheless, the fast convergence of the process is a key factor to limit the cost of the mirror plate production. A deeper characterization of removal function stability showed that its repeatability between each run has to be improved for a real enhancement of the process convergence factor. A new algorithm based on de-convolution has been implemented and tested, with important advantages in terms of calculation speed, minimum material removal and optimization possibilities. By analysing the metrological data of test slumped glasses, we showed how the IBF is effective in the correction of figure errors on scales above 8 - 10 mm. An overall figuring time of few hours is required with surface error around 100 nm rms. Thanks to the thickness measurement data, which are performed in transmission mode with an interferometric set-up, we demonstrated that it is possible to disentangle the effective amount of the material removed and the deformations introduced during the process.

The future of x-ray astronomy depends upon development of x-ray telescopes with larger aperture areas (approx. = 3 square meters) and fine angular resolution (approx. = 1 inch). Combined with the special requirements of nested grazing-incidence optics, the mass and envelope constraints of space-borne telescopes render such advances technologically and programmatically challenging. Achieving this goal will require precision fabrication, alignment, mounting, and assembly of large areas (approx. = 600 square meters) of lightweight (approx. = 1 kilogram/square meter areal density) high-quality mirrors at an acceptable cost (approx. = 1 million dollars/square meter of mirror surface area). This paper reviews relevant technological and programmatic issues, as well as possible approaches for addressing these issues-including active (in-space adjustable) alignment and figure correction.

Addressing the astrophysical problems of the 2020's requires sub-arcsecond x-ray imaging with square meter effective area. Such requirements can be derived, for example, by considering deep x-ray surveys to find the young black holes in the early universe (large redshifts) which will grow into the first supermassive black holes. We have envisioned a mission based on adjustable x-ray optics technology, in order to achieve the required reduction of mass to collecting area for the mirrors. We are pursuing technology which effects this adjustment via thin film piezoelectric "cells" deposited directly on the non-reflecting sides of thin, slumped glass. While SMARTX will also incorporate state-of-the-art x-ray cameras, the remaining spacecraft systems have no more stringent requirements than those which are well understood and proven on the current Chandra X-ray Observatory.

Post-mounting figure correction is a promising avenue to produce low-mass, high-resolution X-ray telescopes. We have demonstrated the feasibility of this approach using piezoelectrically adjustable glass mirrors. Influence functions for various piezoelectric cells have previously been measured with an optical profilometer, but with significant noise. We have improved on both the speed and accuracy of these measurements using a Shack- Hartmann wavefront sensing system. Additionally, we have altered our wavefront sensing system to investigate the mid frequency roughness of our slumped glass mirrors. We report on initial results for measurements of both influence functions and mid frequency roughness and describe our path forward.

The direct deposition of piezoelectric thin films on thin substrates offers an appealing technology for the realization of lightweight adjustable mirrors capable of sub-arcsecond resolution. This solution will make it possible to realize X-ray telescopes with both large effective area and exceptional angular resolution and, in particular, it will enable the realization of the adjustable optics for the proposed mission Square Meter Arcsecond Resolution X-ray Telescope (SMART-X). In the past years we demonstrated for the first time the possibility of depositing a working piezoelectric thin film (1-5 um) made of lead-zirconate-titanate (PZT) on glass. Here we review the recent progress in film deposition and influence function characterization and comparison with finite element models. The suitability of the deposited films is analyzed and some constrains on the piezoelectric film performances are derived. The future steps in the development of the technology are described.

In the half century since the initial discovery of an astronomical (non-solar) x-ray source, the sensitivity for detection of cosmic x-ray sources has improved by ten orders of magnitude. Largely responsible for this dramatic progress has been the refinement of the (grazing-incidence) focusing x-ray telescope. The future of x-ray astronomy relies upon the development of x-ray telescopes with larger aperture areas (greater than 1 m2) and finer angular resolution (less than 1.). Combined with the special requirements of grazing-incidence optics, the mass and envelope constraints of space-borne telescopes render such advances technologically challenging.requiring precision fabrication, alignment, and assembly of large areas (greater than 100 m2) of lightweight (approximately 1 kg m2 areal density) mirrors. Achieving precise and stable alignment and figure control may entail active (in-space adjustable) x-ray optics. This paper discusses relevant programmatic and technological issues and summarizes progress toward active x-ray telescopes.

The next generation of large X-ray telescopes with sub-arcsecond resolution will require very thin, highly nested grazing incidence optics. To correct the low order figure errors resulting from initial manufacture, the mounting process, and the effects of going from 1 g during ground alignment to zero g on-orbit, we plan to adjust the shapes via piezoelectric “cells” deposited on the backs of the reflecting surfaces. This presentation investigates how well the corrections might be made. We take a benchmark conical glass element, 410×205 mm, with a 20×20 array of piezoelectric cells 19×9 mm in size. We use finite element analysis to calculate the influence function of each cell. We then simulate the correction via pseudo matrix inversion to calculate the stress to be applied by each cell, considering distortion due to gravity as calculated by finite element analysis, and by putative low order manufacturing distortions described by Legendre polynomials. We describe our algorithm and its performance, and the implications for the sensitivity of the resulting slope errors to the optimization strategy.

We report on technical progress made over the past year developing thin film piezoelectric adjustable grazing incidence optics. We believe such mirror technology represents a solution to the problem of developing lightweight, sub-arc second imaging resolution X-ray optics. Such optics will be critical to the development next decade of astronomical X-ray observatories such as SMART-X, the Square Meter Arc Second Resolution X-ray Telescope. SMART-X is the logical heir to Chandra, with 30 times the collecting area and Chandra-like imaging resolution, and will greatly expand the discovery space opened by Chandra’s exquisite imaging resolution. In this paper we discuss deposition of thin film piezoelectric material on flat glass mirrors. For the first time, we measured the local figure change produced by energizing a piezo cell – the influence function, and showed it is in good agreement with finite element modeled predictions. We determined that at least one mirror substrate material is suitably resistant to piezoelectric deposition processing temperatures, meaning the amplitude of the deformations introduced is significantly smaller than the adjuster correction dynamic range. Also, using modeled influence functions and IXO-based mirror figure errors, the residual figure error was predicted post-correction. The impact of the residual figure error on imaging performance, including any mid-frequency ripple introduced by the corrections, was modeled. These, and other, results are discussed, as well as future technology development plans.

Adjustable x-ray optics offer the promise of much higher imaging resolution with lightweight optics, providing the key technology for the development of the next generation of astronomical x-ray telescopes such as Generation-X. These adjustable grazing incidence optics might be adjusted only once, on-orbit. To produce theses optics will require the development of several component technologies along with their integration into a new mirror concept. In this paper we define a number of the key technologies necessary for adjustable x-ray optics for astronomy, give a brief description of the issues involved, and some status of these activities being developed as part of our adjustable optics development program at the Smithsonian Astrophysical Observatory.

The Chandra X-ray Observatory , with its sub-arc second resolution, has revolutionized X-ray astronomy by revealing an extremely complex X-ray sky and demonstrating the power of the X-ray window in exploring fundamental astrophysical problems. Larger area telescopes of still higher angular resolution promise further advances. We are engaged in the development of a mission concept, Generation-X, a 0.1 arc second resolution x-ray telescope with tens of square meters of collecting area, 500 times that of Chandra . To achieve these two requirements of imaging and area, we are developing a grazing incidence telescope comprised of many mirror segments. Each segment is an adjustable mirror that is a section of a paraboloid or hyperboloid, aligned and figure corrected in situ on-orbit. To that end, finite element analyses of thin glass mirrors are performed to determine influence functions for each actuator on the mirrors, in order to develop algorithms for correction of mirror deformations. The effects of several mirror mounting schemes are also studied. The finite element analysis results, combined with measurements made on prototype mirrors, will be used to further refine the correction algorithms.

The next large x-ray astrophysics mission launched will likely include soft x-ray spectroscopy as a primary capability. A requirement to fulfill the science goals of such a mission is a large-area x-ray telescope focusing sufficient x-ray flux to perform high-resolution spectroscopy with reasonable observing times. The IXO soft x-ray telescope effort in the US is focused on a tightly nested, thin glass, segmented mirror design. Fabrication of the glass segments with the required surface accuracy is a fundamental challenge; equally challenging will be the alignment of the ~7000 secondary mirror segments with their corresponding primary mirrors, and co-alignment of the mirror pairs. We have developed a system to perform this alignment using a combination of a coordinate measuring machine (CMM) and a double-pass Hartmann test alignment system. We discuss the technique, its ability to correct low-order mirror errors, and results of a recent pair alignment including progress toward the required alignment accuracy of < 2 arcseconds, and discuss the influence of the alignment process on mirror figure. We then look forward toward its scalability to the task of building the IXO telescope.

High-energy astrophysics is a relatively young scientific field, made possible by space-borne telescopes. During the half-century history of x-ray astronomy, the sensitivity of focusing x-ray telescopes-through finer angular resolution and increased effective area-has improved by a factor of a 100 million. This technological advance has enabled numerous exciting discoveries and increasingly detailed study of the high-energy universe-including accreting (stellar-mass and super-massive) black holes, accreting and isolated neutron stars, pulsar-wind nebulae, shocked plasma in supernova remnants, and hot thermal plasma in clusters of galaxies. As the largest structures in the universe, galaxy clusters constitute a unique laboratory for measuring the gravitational effects of dark matter and of dark energy. Here, we review the history of high-resolution x-ray telescopes and highlight some of the scientific results enabled by these telescopes. Next, we describe the planned next-generation x-ray-astronomy facility-the International X-ray Observatory (IXO). We conclude with an overview of a concept for the next next-generation facility-Generation X. The scientific objectives of such a mission will require very large areas (about 10000 m2) of highly-nested lightweight grazing-incidence mirrors with exceptional (about 0.1-arcsecond) angular resolution. Achieving this angular resolution with lightweight mirrors will likely require on-orbit adjustment of alignment and figure., Comment: 19 pages, 11 figures, SPIE Conference 7803 "Adaptive X-ray Optics", part of SPIE Optics+Photonics 2010, San Diego CA, 2010 August 2-5

The next large x-ray astrophysics mission launched will likely include soft x-ray spectroscopy as a primary capability. A requirement to fulfill the science goals of such a mission is a large-area x-ray telescope focusing sufficient x-ray flux to perform high-resolution spectroscopy with reasonable observing times. The IXO soft x-ray telescope effort in the US is focused on a tightly nested, thin glass, segmented mirror design. Fabrication of the glass segments with the required surface accuracy is a fundamental challenge; equally challenging will be the alignment of the ~7000 secondary mirror segments with their corresponding primary mirrors, and co-alignment of the mirror pairs. We have developed a system to perform this alignment using a combination of a coordinate measuring machine (CMM) and a double-pass Hartmann test alignment system. We discuss the technique, its ability to correct low-order mirror errors, and results of a recent pair alignment including progress toward the required alignment accuracy of < 2 arcseconds. We then look forward toward its scalability to the task of building the IXO telescope.

Generation-X is being studied as an extremely high resolution, very large area grazing incidence x-ray telescope. Under a NASA Advanced Mission Concepts Study, we have developed a technology plan designed to lead to the 0.1 arcsec (HPD) resolution adjustable optics with 50 square meters of effective area necessary to meet Generation-X requirements. We describe our plan in detail. In addition, we report on our development activities of adjustable grazing incidence optics via the fabrication of bimorph mirrors. We have successfully deposited thin-film piezo-electric material on the back surface of thin glass mirrors. We report on the electrical and mechanical properties of the bimorph mirrors. We also report on initial finite element modeling of adjustable grazing incidence mirrors; in particular, we examine the impact of how the mirrors are supported - the boundary conditions - on the deformations which can be achieved.

Generation-X will be an X-ray observatory with 50 m 2 collecting area at 1 keV and 0.1" angular resolution. A key concept to enable such a dramatic improvement in angular resolution is that the mirror figure will be adjusted on-orbit; e.g., via piezo-electric actuators deposited on the back side of very thin glass and imparting strains in a bi-morph configuration. To make local adjustments to the individual mirror shells we must employ an imaging detector far forward of the focal surface, so that rays from the individual shells can be measured as distinct rings. We simulate this process on a few representative shells via ray-traces of perfect optics, perturbed axially by low order Legendre polynomial terms. This elucidates some of the requirements for the on-orbit measurements, and on possible algorithms to perform the on-orbit adjustment with acceptably rapid convergence.

The Constellation-X Spectroscopy X-ray Telescope (SXT) is a segmented, tightly nested Wolter-I telescope with a requirement of approximately 12.5 Ž half-power diameter (HPD) for the mirro r system. The individual mirror segments are 0.4-mm thick, formed glass, making the task of mounting, alignment and bonding extremely challenging. Over the past year we have developed a series of tools to meet these challenges, the latest of which is an upgrade to the 600-meter x-ray beam line at GSFC. The new facilities allow us to perform full-aperture and sub-aperture imaging tests of mirror segment pairs to locate th e source of deformations and correlate them with our optical metrology. We present the optical metrology of the axial figure and Hartmann focus, x-ray imaging performance predictions based on analysis of the optical metrology, and both full-aperture and sub-aperture x-ray imaging performance of test mirror segment pairs at 8.05 keV. Keywords: X-ray optics, x-ray imaging, metrology, performance prediction, integration and test

Each of the four Spectroscopy X-ray Telescopes (SXT) on Constellation-X contain a mirror assembly comprised of 2600 primary and secondary mirror segments. Critical to the performance of the mirror assemblies is the alignment of secondary to primary, and alignment of mirror pairs to one another. Focus errors must be corrected in order to meet imaging error budgets. The use of segmented mirrors enables unique alignment strategies not feasible with mirror shells of a full revolution. We discuss the relative advantages and disadvantages of two Con-X alignment strategies to minimize focus errors between shells. In the first approach, the mirrors are bent azimuthally to adjust the focal length of the mirror pair. In the second approach, coma is used to compensate for the transverse focus error. We examine the limits of applicability of the two approaches, and also discuss alignment error budgets.

For X-ray astronomy, 0.1 arc-second imaging resolution will result in a significant advance in our understanding of the Universe. Similarly, the advent of low cost high performance X-ray mirrors will also increase the likelihood of more X-ray telescopes being funded and built. We discuss the development plans of two different types of adjustable grazing incidence optics: one being a tenth arc-second resolution bimorph mirror approach also suitable for extremely large collecting areas, and the second being a few arc-second radially adjustable mirror approach more suitable for modest sized telescopes. Bimorph mirrors will be developed using thin (0.1 - 0.4 mm) thermally formed glass or electroplated metal mirror segments with thin film piezo-electric actuators deposited directly on the mirror back surface. Mirror figure will be adjusted on-orbit. Radially adjustable mirrors will employ discreet radially electrostrictive actuators for mirror alignment and low spatial error frequency figure correction during assembly and alignment. In this paper we report on. In this paper we describe mirror design and our development plans for both mirror concepts.

We present an overview update of the metrologic approach to be employed for the segmented mirror fabrication for Constellation-X spectroscopy x-ray telescope. We compare results achieved to date with mission requirements. This is discussed in terms of inherent capability versus in-practice capability. We find that all the needed metrics for the mirrors are in hand but that they are currently limited by the mounting of the mirrors themselves.

著者人数：29名, Accepted: 2007-03-08, 資料番号: SA1000202000

One of the key instruments on the Reconnection and Microscale (RAM) Solar-Terrestrial Probe mission is a normal incidence multilayer x-ray telescope designed to provide 10 milli-arc-sec imaging of the solar corona. To achieve this level of imaging it will be necessary to fabricate meter-class reflective optics with diffraction limited performance at 193 Angstroms. Because of the use of multilayer optics, surface micro-roughness must also be maintained at very low levels (a few Angstroms rms) to maintain good reflectance. To ease fabrication constraints and the sometimes competing requirements of micro-roughness and figure, we have explored a number of potential designs and fabrication approaches for RAM. Figure error budgets and optical designs are shown, demonstrating that RAM can be built with existing mirror fabrication technology.

Recent studies and planning for a variety of x-ray astronomy missions (Constellation-X, XEUS, Generation-X) have driven astronomers to explore grazing incidence telescopes with focal lengths of 50 m or greater. One approach to implementing such long focal lengths is to employ formation flying: separate optic and detector spacecraft travel in formation. Formation flying removes the "telescope tube" which was an integral part of shielding the telescope from straylight. We consider the implications of formation flying with respect to straylight, and discuss some design guidelines for baffling the straylight. The Constellation-X mission is used as an example.

Large collecting area x-ray telescopes are designed to study the early Universe, trace the evolution of black holes, starsand galaxies, study the chemical evolution of the Universe, and study matter in extreme environments. TheConstellation-X mission (Con-X), planned for launch in 2016, will provide ~ 10 4 cm 2 collecting area with 15 arc-secresolution, with a goal of 5 arc-sec. Future missions require larger coll ecting area and finer resolution. Generation-X(Gen-X), a NASA Visions Missio n, will achieve 100 m 2 effective area at 1 keV and angular resolution of 0.1 arc-sec, half power diameter. We briefly describe the Con-X flowdown of imaging requ irements to reflector figure error. Tomeet requirements beyond Con-X, Gen-X optics will be thinner and more accurately shaped than has ever beenaccomplished. To meet these challenging goals, we incorporate for the first time active figure control with grazing incidence optics. Piezoelectric material will be deposited in discrete cells directly on the back surface of the optical segments, with the strain directions oriented parallel to the surface. Differential strain between the two layers of the mirror causes localized bending in two directions, enablin g local figure control. Adjusting figure on-orbit eases fabrication and metrology. The ability to make changes to mirro r figure adds margin by mitigating risk due to launch-induced deformations and/or on-orbit degradation. We flow down the Gen-X requirements to mirror figure and fourtelescope designs, and discuss various trades between the designs.Keywords: x-ray optics, active optics, adjustable optics, Con-X, Gen-X

We present the metrology requirements and metrology implementation necessary to optically characterize the reflector technology for the Constellation-X (C-X) spectroscopy x-ray telescope (SXT). This segmented, 1.6m diameter highly nested telescope presents many metrology and alignment challenges. In particular, these mirrors have a stringent imaging error budget as compared to their intrinsic stiffness. The low stiffness is seen to be implied by the required effective area and the required weight. The low mirror stiffness has implications for the metrology that can be used. A variety of contact and non-contact optical profiling and interferometric methods are combined to test the formed glass substrates before replication and the replicated reflector segments. The reflectors are tested both stand-alone and in-situ in an alignment tower. 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 high precision coordinate measurement machines using very low force or optical probes, axial interferometric profiling, azimuthal circularity profiling, and use of advanced null optics such as conical computer generated hologram (CGHs).

The new frontier in astrophysics is the study of the very first stars, galaxies and black holes in the early Universe. These objects are beyond the grasp of the current generation of X-ray telescopes such as Chandra, and so the Generation-X Vision Mission has been proposed as an X-ray observatory which will be capable of detecting these earliest objects. Xray imaging and spectroscopy of such distant objects will require an X-ray telescope with large collecting area and high angular resolution. The Generation-X concept has 100 m2 collecting area at 1 keV (1000 times larger than Chandra) and 0.1 arcsecond angular resolution (several times better than Chandra and 50 times better than the resolution goal for Constellation-X). The baseline mission involves four 8 m diameter telescopes operating at Sun-Earth L2. Such large telescopes will require either robotic or human-assisted in-flight assembly. To achieve the required effective area with launchable mass, very lightweight grazing incidence X-ray optics must be developed, having an areal density 100 times lower than in Chandra, with perhaps 0.1 mm thick mirrors requiring on-orbit figure control. The suite of available detectors for Generation-X should include a large-area high resolution imager, a cryogenic imaging spectrometer and a grating spectrometer.

The Constellation-X Spectroscopy X-ray telescope (SXT) is designed to be built from X-ray optic segments. The X-ray segments will be fabricated from the segmented mandrels using a replication process. The purpose of the incoming metrology is to map the surface of the mandrels, so the performance of the X-ray optics produced can be predicted. Three Constellation-X segmented mandrels have been delivered to MSFC for incoming metrology. The segmented mandrels are 30-degree sections of a cylindrical surface and have diameters of 1.0 m, 1.2 m and 1.6 m. The maximum dimensions of the optical surface are 1.0 m axial length and 0.5 m azimuthal segment length. The metrology of the mandrels consists of the measurement of their slope differences, roundness, absolute radius, axial profile and microroughness. Accuracy goals for each type of measurement and the accuracy of the instruments used for the measurements will be discussed. The results of the mandrel metrology together with the performance predictions will be presented.

The solar x-ray imager (SXI) is a grazing incidence Wolter Type I X-ray Telescope to be fabricated and flown on the National Oceanic and Atmospheric Administration's (NOAA) Geo-Stationary Operational Environmental Satellite. The SXI will image the full sun at wavelengths between approximately 6 and 60 angstroms with a detector having 5 arc sec pixels. The goal for SXI is to forecast 'space weather', i.e., effects of charged particles that are produced at the Sun as they interact at the earth. Major contributors to space weather include: variations in the Sun's solar wind, solar flares, and solar mass ejections. Effects of space weather include: radiation damage and particle events in high- inclination orbit spacecraft, disruption of various kinds of communications equipment, degradation of navigational tools such as GPS, potential health hazard during space walks, and power blackouts the SXI and the resulting optical design for the grazing incidence telescope. Parametric performance predictions of image quality as degraded by diffraction, geometrical aberrations, and surface scattering effects due to residual optical fabrication errors are presented that establish realistic optical fabrication tolerances necessary to satisfy top-level image quality requirements.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Orthonormal polynomials have long been used as a convenient tool to describe optic surface errors. Previously, the products of Fourier and Legendre polynomials have been employed to describe the surface errors for grazing incidence optics. We have applied an alternate set of polynomials, Fourier-Fourier polynomials, to describe the surface errors. This new set differs functionally from the Fourier Legendre set in that each term has a finite bandwidth frequency spectrum. The advantages of this difference with respect to predictions of grazing incidence telescope performance based on measured surface figure errors are discussed.

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