This PDF file contains the Front Matter associated with SPIE Proceedings Volume 7803, including the Title page, Copyright information, Table of Contents, Conference Committee listing, and Introduction.

We report on the design and performances of a test prototype active X-ray mirror developed for the French national synchrotron radiation facility SOLEIL in collaboration with a French company ISP System. The active mirror uses 11 mechanical actuators: one actuator for the main curvature and 10 actuators along the mirror surface for correction of the residual shape errors. Its radius of curvature can be adjusted from infinity down to 50 m, with residual slope errors in correction less than 0.6 μrad RMS over a 300 mm useful length. A dedicated X-ray Hartmann wavefront sensor, based on YAG:Ce wavelength conversion to visible light, was developed for feedback control of the mirror. Closed-loop experiments were performed at 10 keV on the Metrology and Tests Beamline at SOLEIL.

We present the design, fabrication and characterization of a novel adaptive X-ray optic by bringing together bimorph adaptive technology and the novel Elastic Emission Machining "super-polishing" technique. This super-polished adaptive mirror provides variable focal distance and local figure control in the sub-nm range. The optic has the potential to generate distortion-free beams, and enable wavefront control.

In the hard X-ray region, to obtain the theoretical resolution or diffraction limited focusing size in an imaging optical system, both ultraprecise optics and highly accurate alignment are necessary. An adaptive optical system is used for the compensation of aberrations in various optical systems, such as optical microscopes and space telescopes. In situ wavefront control of hard X-rays is also effective for realizing ideal performance. The aim of this paper is to develop an adaptive optical system for sub-10nm hard X-ray focusing. The adaptive optical system performs the wavefront measurement using a phase retrieval algorithm and wavefront control using grazing incidence deformable mirrors. Several results of experiments using the developed system are reported.

The Smart X-Ray Optics (SXO) project comprises a U.K.-based consortium developing active/adaptive micro-structured optical arrays (MOAs). These devices are designed to focus X-rays using grazing incidence reflection through consecutive aligned arrays of microscopic channels etched in silicon. Adaptability is achieved using a combination of piezoelectric actuators, which bend the edges of the silicon chip, and a spider structure, which forms a series of levers connecting the edges of the chip with the active area at the centre, effectively amplifying the bend radius. Test spider structures, have been bent to a radius of curvature smaller than 5 cm, indicating that in complete devices a suitable focal length using a tandem pair configuration could be achieved. Finite Element Analysis (FEA) modelling has been carried out for the optimization of the spider MOA device design. Prototype devices have been manufactured using a Viscous Plastic Processing technique for the PZT piezoelectric actuators, and a single wet etch step using {111} planes in a (110) silicon wafer for both the silicon channels and the spider structure. A surface roughness of 1.2 nm was achieved on the silicon channel walls. Characterisation techniques have been developed in order to evaluate the device performance in terms of the bending of the MOA channels produced by the actuators. This paper evaluates the progress to date on the development of spider MOA's comparing FEA modelling with the results obtained for prototype structures.

Adaptive angular control of reflecting crystals is crucial for reliable operation of high-resolution x-ray optics at synchrotron radiation facilities. An anglular compensation with nanoradian tolerance is required for some advanced applications. We present a working solution, a null-detection feedback system which was successfully applied for stabilization of an x-ray monochromator with energy resolution of ΔE/E ≈ 10⁻⁸(E = 23.7 keV). Another possible application of the feedback system, stabilization of optical cavity for x-ray free electron laser oscillator (XFELO) is discussed.

Adaptive X-ray optics offer significant potential for new optical systems. An analysis and design tool for the optomechanical design of adaptive X-ray optics is presented. The key issues addressed are: 1) The processing of finite element nodal displacements for optical surface characterization is illustrated. 2) The fitting of Fourier-Legendre polynomials to the radial sag or surface normal displacements of near cylindrical optics is presented. 3) The use of 2D Legendre polynomials are presented as an alternative representation of mechanical displacements. 4) The analysis of adaptive X-ray optics requires the solution of actuator strokes required to minimize surface RMS. Issues include stroke limits and surface slope error minimization. 5) The number and placement of actuators can be optimized by using an embedded genetic selection algorithm. 6) The mirror structure and mounts may be optimized to minimize the adaptively corrected surface error while still satisfying all structural requirements. 7) The implementation of a Monte Carlo technique to predict the impact of random factors in the system such as actuator resolution or mount strain forces.

We discuss a technique of shape modification that can be applied to thin walled (~100-400 micron thickness) electroformed replicated optics or slumped glass optics to improve the near net shape of the mirror as well as the midfrequency ripple. The process involves sputter deposition of a magnetic smart material (MSM) film onto a permanently magnetic material. The MSM material exhibits strains about 400 times stronger than ordinary ferromagnetic materials. The deformation process involves a magnetic write head which traverses the surface, and under the guidance of active metrology feedback, locally magnetizes the surface to impart strain where needed. Designs and basic concepts as applied to space borne X-ray optics will be described.

This review on Active Optics Methods presents various concepts of deformable uv, visible and ir telescope optics which have been mainly developed at the Marseille Observatory - for now 40 years - and other institutes. An optical surface generated by active optics and spherical figuring is free from high spatial frequency errors i.e. ripple errors. Active Optics allows applications of new concepts as: stress figuring aspherization processes, variable curvature mirrors, in situ stressing aspherization processes, under stress replications to generate corrected diffraction gratings, multimode deformable compensators, and situ control of large telescope optics. X-ray telescope mirrors could also benefit soon from the enhanced imaging performances of active optics. The 0.5- 1 arcsec spatial resolution of Chandra should be followed up by increased resolution space telescopes. This requires constructing new grazing-incidence telescopes which will strictly satisfy Abbe's sine condition, i.e. a Chase-VanSpeybroeck design for the two-mirror case. The recent elaboration of an elasticity theory of weakly conical shells allows reviewing some potential innovative concepts for the active figuring and in situ control of either monolithic or segmented telescope mirrors for x-ray astronomy.

We report experimental results of our normal-incident EUV telescope tuned to a 13.5 nm band, with an adaptive optics. The optics consists of a spherical primary mirror and a secondary deformable mirror. A laser plasma source irradiates optical and EUV lights to the system. The system also equips a reference laser, optical light from which are nearly spherical and reflected by mirrors through the light path along the objective light. We controlled the deformable mirror to correct the wave form by referring that of the reference laser. At first, we attempted a normal AO control, where we controlled deformable mirror so that the wave form of the reference laser becomes spherical. Although we verified an improvement of angular resolution with this method, the resolution is not good enough comparing with the diffraction limit. The degradation is due to the difference between the paths of objective light and the reference laser. Then we modify the target wave form to control the deformable mirror, as the EUV image becomes best. We confirmed the validity of this control and performed a 2.1 arcsec resolution in both optical and EUV lights.

The Naval Prototype Optical Interferometer (NPOI) is the longest baseline interferometer operating at visible wavelengths in the world. The astronomical capabilities of such an instrument are being exploited and recent results will be presented. NPOI is also the largest optical telescope belonging to the US Department of Defense with a maximum baseline of 435 meter has a resolution that is approximately 181 times the resolution attainable by the Hubble Space Telescope (HST) and 118 times the resolution attainable by the Advanced Electro-Optical System (AEOS). It is also the only optical interferometer capable of recombining up to six apertures simultaneously. The NPOI is a sparse aperture and its sensitivity is limited by the size of the unit aperture, currently that size is 0.5 meters. In order to increase the overall sensitivity of the instrument a program was started to manufacture larger, 1.4 meter, ultra-light telescopes. The lightness of the telescopes requirement is due to the fact that telescopes have to be easily transportable in order to reconfigure the array. For this reason a program was started three years ago to investigate the feasibility of manufacturing Carbon Fiber Reinforced Polymer (CFRP) telescopes, including the optics. Furthermore, since the unit apertures are now much larger than r0 there is a need to compensate the aperture with adaptive optics (AO). Since the need for mobility of the telescopes, compact AO systems, based on Micro-Electro-Mechanical-Systems (MEMS), have been developed. This paper will present the status of our adaptive optics system and some of the results attained so far with it.

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 (stellarmass 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.

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.

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.

In the context of the AHEAD project of the FP7 European call, a group of UK and Italian Institutions is proposing a research on X-ray optics that can provide large collecting areas (a few decades of m²) combined with a high angular resolution (0.1-1 arcsec). This requires the development of Active X-ray Optics in which the reflecting surfaces can be adjusted-manipulated in order to achieve and maintain the correct shape. In the context of an international collaboration with UK institutes, the Astronomical Observatory of Brera (INAF-OAB) is in charge of the production of thin (0.4 mm or less) glass mirror segments for the demonstration of a 2-reflection active X-ray system including piezoelectric actuators to improve the angular resolution, For the shell segments production the hot slumping approach of glass foils, already under investigation for the realization of IXO mirrors, is adopted. In this paper, a detailed description of the method is presented, reporting also on the metrological data of produced samples.

In this paper we present the "Characterization Universal Profilometer" (CUP), a new metrological instrument developed at the Brera Observatory for the 3D surface figure mapping of X-ray segmented mirrors. The CUP working principle is based on the measure of the the distance between the surface under test from a rigid reference dish. This approach is made possible by the coupled use of two sensors, the CHRocodile® optical device and the SIOS triple beam interferometer, mounted onto a proper system of x-y-z stage of translators. In this paper we describe the working principle of the new instrument. We will also present the results of the commissioning performed for a CUP breadboard developed at the Brera Observatory. The CUP offers the possibility to perform an high accuracy metrology of thin glass segments produced via hot slumping, to be used in future segmented X-ray mirrors like those foreseen aboard IXO or other projects that will make use of active X-ray mirrors.

The design of current X-ray telescope systems needs to reach a compromise between the resolution and sensitivity. A new area of interest of adaptive optics is the development of actively controlled thin X-ray mirrors, where aberrations would be corrected. Their assembly on an X-ray telescope would provide an instrument with both high resolution and sensitivity. The Smart X-Ray Optics (SXO) project comprises a U.K.-based consortium developing prototypes for the next generation of X-ray telescopes. The overall aim is to produce X-ray mirrors using thin, below 1mm, structures, comprising Ni mirror shells with bonded piezoelectric unimorph actuators, and with a target resolution of ~0.1 arcs. Such an optic would enable the design of an X-ray telescope with both a greater resolution and collective area than the best currently available by Chandra (0.5arcs) and XMM Newton (1650cm²) respectively. Lead zirconate titanate, PZT-based piezoelectric actuators are being developed in this programme to fit precisely the curved Ni mirror shell prototypes (100×300×0.4mm, radius of curvature 167mm). Viscous plastic processing has been chosen for the fabrication of net-shaped piezoelectric unimorph actuators 75×32×0.18mm, with radius of curvature conforming to those of the X-ray optic. Laser machining has been used for precisely controlling the actuator shape and for the definition of the multi-segment electrodes. Accurate control of the thickness, surface finish and curvature are the key factors to delivering satisfactory actuators. Results are presented concerning the fabrication and characterisation of the piezoelectric actuators, and the integration procedure on the nickel optic.

The Smart X-ray Optics project is a UK based consortium of five institutions investigating active/adaptive X-ray optics for both large and small scale applications. The large scale application is aimed towards future X-ray telescopes for X-ray astronomy. The work presented here includes the modelling and the testing of the new large scale prototype thin shell optic which incorporates piezoelectric devices to enable the surface to be actively deformed aiming to achieve an angular resolution better than that currently available (e.g. Chandra 0.5"). As the shell is thin, a high degree of nesting is possible such that very large collecting areas can be provided in combination with the high angular resolution. The results from the testing campaign for this prototype in the X-ray beam line at the University of Leicester will be presented. The effect of the actuated piezoelectric devices on the detected image and software development for control of the system are discussed. Improvement of the Full width Half Maximum of the focus spot of up to 25% was seen but as yet this has not been completed in a controlled way. The surface figure achieved with a given set of voltages is stable, but an apparent interaction or coupling between the piezoelectric devices was detected and is still unexplained.

The proposed adaptive optics system for the Gen-X telescope uses piezoelectric lead zirconate titanate (PZT) films deposited on flexible glass substrates. The low softening transition of the glass substrates imposes several processing challenges that require the development of new approaches to deposit high quality PZT thin films. Synthesis and optimization of chemical solution deposited 1 μm thick films of PbZr_0.52Ti_0.48O₃ on small area (1 in²) and large area (16 in²) Pt/Ti/glass substrates has been performed. In order to avoid warping of the glass at temperatures typically used to crystallize PZT films (~700°C), a lower temperature, two-step crystallization process was employed. An ~80 nm thick seed layer of PbZr_0.30Ti_0.70O₃ was deposited to promote the growth of the perovskite phase. After the deposition of the seed layer, the films were annealed in a rapid thermal annealing (RTA) furnace at 550°C for 3 minutes to nucleate the perovskite phase. This was followed by isothermal annealing at 550°C for 1 hour to complete crystallization. For the subsequent PbZr_0.52Ti_0.48O₃ layers, the same RTA protocol was performed, with the isothermal crystallization implemented following the deposition of three PbZr_0.52Ti_0.48O₃ spin-coated layers. Over the frequency range of 1 kHz to 100 kHz, films exhibit relative permittivity values near 800 with loss tangents below 0.07. Hysteresis loops show low levels of imprint with coercive fields of 40-50 kV/cm in the forward direction and 50-70 kV/cm in the reverse direction. The remanent polarization varied from 25-35 μC/cm² and e_31,f values were approximately -5.0 C/m². In scaling up the growth procedure to large area films, where warping becomes more pronounced due to the increased size of the substrate, the pyrolysis and crystallization conditions were performed in a box furnace to improve the temperature uniformity. By depositing films on both sides of the glass substrate, the tensile stresses are balanced, providing a sufficiently flat surface to continue PZT deposition. The properties of the large area film are comparable to those obtained on small substrates. While sol-gel processing is a viable approach to the deposition of high quality PZT thin films on glass substrates, preliminary results using RF magnetron sputter deposition demonstrate comparable properties with a significantly simpler process that offers a superior route for large scale production.

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.

Advances in X-ray astronomy require high spatial resolution and large collecting area. Unfortunately, X-ray telescopes with grazing incidence mirrors require hundreds of concentric mirror pairs to obtain the necessary collecting area, and these mirrors must be thin shells packed tightly together... They must also be light enough to be placed in orbit with existing launch vehicles, and able to be fabricated by the thousands for an affordable cost. The current state of the art in X-ray observatories is represented by NASA's Chandra X-ray observatory with 0.5 arc-second resolution, but only 400 cm² of collecting area, and by ESA's XMM-Newton observatory with 4,300 cm² of collecting area but only 15 arc-second resolution. The joint NASA/ESA/JAXA International X-ray Observatory (IXO), with ~15,000 cm² of collecting area and 5 arc-second resolution which is currently in the early study phase, is pushing the limits of passive mirror technology. The Generation-X mission is one of the Advanced Strategic Mission Concepts that NASA is considering for development in the post-2020 period. As currently conceived, Gen-X would be a follow-on to IXO with a collecting area ≥ 50 m², a 60-m focal length and 0.1 arc-second spatial resolution. Gen-X would be launched in ~2030 with a heavy lift Launch Vehicle to an L2 orbit. Active figure control will be necessary to meet the challenging requirements of the Gen-X optics. In this paper we present our adaptive grazing incidence mirror design and the results from laboratory tests of a prototype mirror.