This PDF file contains the front matter associated with SPIE Proceedings Volume 7437, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

The International X-ray Observatory (IXO) is a candidate mission in the ESA Space Science Programme Cosmic Visions 2015-2025. IXO is being studied as a joint mission with NASA and JAXA. The mission concept and X-ray telescope accommodation have both been studied in the ESA Concurrent Design Facility. Competitive industrial studies will now further investigate the issues raised, and will elaborate mission concepts. In parallel the required technologies are being developed, with the main emphasis under ESA responsibility being focused on Silicon Pore Optics (SPO). A technology development plan has been made and its implementation is progressing well. The paper presents a summary of the ESA system studies of IXO and provides an overview of the related ESA led technology preparation activities.

Astro-H mission is the new Japanese X-ray mission following Suzaku. One of the unique features of the mission is an imaging spectroscopy in a unprecedentedly wide energy region from 0.3 to 60 keV. The X-Ray Telescope (XRT) system covers the energy region by means of grazing incidence reflective optics. In the current baseline specification, the XRT system consists of two hard X-ray telescopes (HXTs) which cover 5 to 60 keV, and two soft X-ray telescopes (SXT-S and SXT-I) which cover 0.3 to about 10 keV. Both of HXT and SXT-S mirrors employ tightly-nested, conicallyapproximated thin-foil Wolter-I optics. The HXTs employ Pt/C depth-graded multilayers (supermirrors), while the SXTS employ a single layer of gold. We measured test reflectors for Astro-H HXT at SPring-8, and obtained the roughness of the test reflectors of < 4 A and the image blur after two reflections of 0.8'-1.1'. International collaboration has been formed for the project, and basic and design studies have been carried out. Based on the basic study, detailed studies of the flight design are in progress, and production facilities for the Astro-H XRT system are close to complete.

The New Hard X-ray Mission (NHXM) Italian project will be operated by 2016. It is based on 4 hard X-ray optics modules, each formed by 60 evenly spaced multilayer coated Wolter I mirror shells. For the achievement of a long focal length (10 m) an extensible bench is used. The pseudo-cylindrical Wolter I monolithic substrates where the multilayer coating is applied will be produced using the Ni electroforming replica approach. For three of the four mirror modules the focal plane will host a hybrid a detector system, consisting in the combination of a Si-based low energy detector (efficient from 0.5 up to ~ 15 keV) , on top of a high energy CdTe pixellated detector (efficient from 10 keV up to ~ 80 keV); the two cameras will be surrounded by both a passive shield and an anticoincidence shield. The total on axis effective area of the three telescopes at 1 keV and at 30 kev is of 1500 cm² and 350 cm² respectively. The angular resolution requirement is better than 20 arcsec HEW at 30 keV, while the Field of View at 50% vignetting is 12 arcmin (diameter). The payload is finally completed with the fourth telescope module, that will have as a focal plane detector a high sensitivity imaging photoelectric polarimetric system, operating from 2 up to 35 keV. In this paper, after an overview of the mission configuration and its scientific goals, we report on the design and development of the multilayer optics of the mission, based on thin replicated Ni mirror shells.

The Focusing Optics x-ray Solar Imager (FOXSI) is a sounding rocket payload funded under the NASA Low Cost Access to Space program to test hard x-ray focusing optics and position-sensitive solid state detectors for solar observations. Today's leading solar hard x-ray instrument, the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) provides excellent spatial (2 arcseconds) and spectral (1 keV) resolution. Yet, due to its use of indirect imaging, the derived images have a low dynamic range (<30) and sensitivity. These limitations make it difficult to study faint x-ray sources in the solar corona which are crucial for understanding the solar flare acceleration process. Grazing-incidence x-ray focusing optics combined with position-sensitive solid state detectors can overcome both of these limitations enabling the next breakthrough in understanding particle acceleration in solar flares. The FOXSI project is led by the Space Science Laboratory at the University of California. The NASA Marshall Space Flight Center, with experience from the HERO balloon project, is responsible for the grazing-incidence optics, while the Astro H team (JAXA/ISAS) will provide double-sided silicon strip detectors. FOXSI will be a pathfinder for the next generation of solar hard x-ray spectroscopic imagers. Such observatories will be able to image the non-thermal electrons within the solar flare acceleration region, trace their paths through the corona, and provide essential quantitative measurements such as energy spectra, density, and energy content in accelerated electrons.

The Energetic X-ray Imaging Survey Telescope (EXIST) is a mission that has been studied for the NASA Physics of the Cosmos Program. EXIST will continuously survey the full sky by scanning for 2-years (with 2-3 interruptions per day for GRB follow-up) followed by a 3-years pointing phase. The mission includes three instruments: a High Energy coded mask Telescope; a 1.1m aperture optical-IR Telescope; and a Soft X-ray Imager (SXI), sensitive in the 0.1-10 keV band. SXI is proposed as a contribution of ASI-Italy, fully developed by Italian institutes. The current optical design foresees 26 shells providing an effective area comparable to one XMM-Newton mirror module up to 3 keV and somewhat lower from 3 to 10 keV. The realization of these shells is based on the well-proven Nichel replication-process technology. Here we will present the optical design of the SXI mirror module and describe its characteristics in term of effective area and imaging capability, summarizing also the characteristics of the full SXI telescope.

The Spectrum-Roentgen-Gamma mission will be launched in the 2012 year into a L2 orbit with Soyuz launcher and Fregat buster from Baikonur. The mission will conduct all-sky survey with X-ray mirror telescopes eROSITA and ART-XC up to 11 keV. It will allow detection of about 100 thousand clusters of galaxies and discovery large scale Universe structure. It will also discover all obscured accreting Black Holes in nearby galaxies and many (about 3 millions) new distant AGN. Then it is planned to observe dedicated sky regions with high sensitivity and thereafter to perform follow-up pointed observations of selected sources.

We present the current state of the development system of the hard ray telescope onboard ASTRO-H satellite. Japan's 6th X-ray satellite mission ASTRO-H, which is planed to be launched in fiscal year 2013, will carry four X-ray telescopes (XRT). Two of four XRTs are hard X-ray telescopes (HXT) using depth-graded multilayer reflector which provide us the capability of hard X-ray imaging observation up to 80 keV. ASTRO-H/HXT is the light-weight hard X-ray telescope using Pt/C depth-graded multilayer and high-throughput thin-foil optics. The basic technology for fabricating the ASTRO-H/HXT has been established through the balloon borne experiments, "InFOCμS" (US-Japan international joint experiment) and "SUMIT" missions. (Nagoya University, Osaka University and JAXA). Major changes from XRTs onboard InFOCμS and SUMIT missions are large aperture size of 45 cm in diameter, the length of reflectors of 20 cm and the focal length of 12 m (XRTs onboard the balloon missions above have the aperture size of 40 cm in diameter, 13 cm long reflectors and 8 m focal length). Now we have almost finished to establish the mirror production facility dedicated to the ASTRO-H/HXT and are starting to produce foil reflectors for performance verification of 200 mm long reflector. We report the current status of the development facilities and test foil production.

The Flight Mirror Assembly (FMA) preliminary mechanical design for NASA's next major X-ray telescope mission, the International X-Ray Observatory (IXO), has been developed at NASA Goddard Space Flight Center (GSFC). The design addresses some unique engineering challenges presented by the unprecedented combination of high angular resolution and large effective area required to achieve the desired scientific objectives. To meet these requirements, the Wolter-I Soft X-Ray Telescope (SXT) optical design consists of about 14,000 0.4 mm thick glass mirror segments densely packed into a 3.4 m diameter FMA and supported with micron level accuracy and stability. Key engineering challenges addressed include ensuring positive stress margins for the glass segments with a high Factor of Safety, keeping the structure light enough to launch, providing a large effective area, and preventing unacceptable thermal distortion. Standard mechanical design techniques such as FEM modeling and optimization, integrated optomechanical analysis, and development testing were applied to this unique problem. The thin mirror segments are mounted into 60 intermediate wedge shaped structures called modules. Modules are kinematically mounted to the FMA primary structure which is optimized for minimum mass and obscuration of the clear aperture. The preliminary design demonstrates the feasibility of building and launching a large space-based SXT using slumped glass mirrors which meets the IXO effective area, mass, structural, and thermal requirements.

A method of constructing a large aperture grazing incidence X-ray telescope utilizing the Kirkpatrick-Baez (K-B) geometry is described. Two crossed stacks of flat, wedged Silicon plates comprise a single optical unit which provides focusing to a angular resolution limit set by the plate separation within the stacks. If high precision Silicon wafers are used and the focal length is large, an angular resolution of a few arc seconds is achievable. As a refinement an angular resolution at the limit imposed by the K-B geometry could be met if the plates were very slightly curved to the correct parabolic profile along the axial direction. A tessellation of a large number of identical or nearly identical stacks over a spherical aperture plane can provide a very large collecting area and high angular resolution suitable for the International X-ray Observatory (IXO) or similar X-ray astronomy applications. The optical design operates in a similar way to the lobster eye geometry and unlimited extension of the aperture coverage (tessellation) can provide a very large field of view suitable for all-sky monitoring.

The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA satellite mission scheduled for launch in 2011. Using focusing optics with multilayer coating for enhanced reflectivity of hard X-rays (6-79 keV), NuSTAR will provide a combination of clarity, sensitivity and spectral resolution surpassing the largest observatories in this band by orders of magnitude. This advance will allow NuSTAR to test theories of how heavy elements are born, discover collapsed stars and black holes on all scales and explore the most extreme physical environments. We will present an overview of the NuSTAR optics design and production process and detail the optics performance.

X-ray mirrors are usually built in the Wolter I (paraboloid-hyperboloid) configuration which provides, in principle, perfect on-axis images. This design exhibits no spherical aberration on-axis but suffers from field curvature, coma and astigmatism, therefore the angular resolution degrades rapidly with increasing off-axis angles. Different mirror designs exist in which the primary and secondary mirror profiles are expanded as a power series in order to increase the angular resolution at large off-axis positions. Here we present the design and global trade off study of an X-ray mirror systems based on polynomial optics in view of the Wide Field X-ray Telescope (WFXT) mission. WFXT aims at performing an extended cosmological survey in the soft X-ray band with unprecedented flux sensitivity. To achieve these goals the angular resolution required for the mission is very demanding, of 5 arcsec HEW resolution goal to be achieved across a 1-deg field of view, in addition an effective area of 5-9000 cm² at 1 keV is needed.

In a X-ray telescope in formation flight configuration, the optics and the focal-plane detectors reside in two different spacecraft. The dynamics of the detector spacecraft (DSC) with respect to the mirror spacecraft (MSC, carrying the mirrors of the telescope) changes continuously the arrival positions of the photons on the detectors. In this paper we analyze this issue for the case of the SIMBOL-X hard X-ray mission, extensively studied by CNES and ASI until 2009 spring. Due to the existing gaps between pixels and between detector modules, the dynamics of the system may produce a relevant photometric effect. The aim of this work is to present the optimization study of the control-law algorithm with respect to the detector's geometry. As the photometric effect may vary depending upon position of the source image on the detector, the analysis-carried out using the simuLOS (INAF, CNES, CEA) simulation tool-is extended over the entire SIMBOL-X field of view.

X-ray telescopes having a relatively wide field-of-view and spatial resolution vs. polar off-axis angle curves much flatter than the parabolic dependence characteristic of Wolter I designs are of great interest for surveys of the X-ray sky and potentially for study of the Sun's X-ray emission. We discuss the various considerations affecting the design of such telescopes, including the possible use of polynomial mirror surface prescriptions, a method of optimizing the polynomial coefficients, scaling laws for mirror segment length vs. intersection radius, the loss of on-axis spatial resolution, and the positioning of focal plane detectors.

We present a high-resolution soft x-ray grating spectrometer concept for the International X-Ray Observatory (IXO) that meets or exceeds the minimum requirements for effective area (> 1, 000 cm² for E < 1 keV) and spectral resolution (E/▵E > 3, 000). At the heart of the spectrometer is an array of recently developed highefficiency blazed transmission gratings, the so-called critical-angle transmission (CAT) gratings. They combine the advantages of traditional transmission gratings (very low mass, extremely relaxed alignment and flatness tolerances) with those of x-ray reflection gratings (high efficiency due to blazing in the direction of grazing-incidence reflection). In addition, a CAT grating spectrometer is well-suited for co-existence with energy-dispersive highenergy focal plane detectors, since most high-energy x rays are neither absorbed, nor diffracted, and contribute to the effective area at the telescope focus. Since our initial successful x-ray demonstrations of the CAT grating concept with large-period and lower aspect-ratio prototypes, we have now microfabricated 200 nm-period silicon CAT gratings comprised of grating bars with the required dimensions (6 micron tall, 40 nm wide, aspect ratio 150), optimized for the 0.3 to 1.0 keV energy band. Preliminary analysis of recent x-ray tests show blazing behavior up to 1.28 keV in accordance with predictions.

A dispersive spectrometer onboard the International X-ray Observatory (IXO) provides a method for high throughput and high spectral resolution at X-ray energies below 1 keV. An off-plane reflection grating array maximizes these capabilities. We present here a mature mechanical design that places the grating array on the spacecraft avionics bus 13.5 m away from the focal plane. In addition, we present the technology development plan for advancing the Technology Readiness Level to 6 for the Off-Plane X-ray Grating Spectrometer.

We present an overview of the Extended X-ray Off-Plane Spectrometer (EXOS) Sounding Rocket Payload based at the University of Colorado, Boulder. The program includes a total of four launches over the next four years on various x-ray sources. The payload utilizes off-plane reflection gratings and Gaseous Electron Multiplier (GEM) detectors in order to achieve both high throughput and resolution (R~100).

X-ray Phase Fresnel lenses (PFLs) can be considered as diffraction gratings with rotational (axial) symmetry and radially-varying pitch. The achromatic combinations of refractive and diffractive lenses that have been proposed for applications in X-ray and gamma-ray astronomy may then be regarded as grisms, again with variable pitch and axial symmetry. This way of looking at optics for very high angular resolution high-energy astronomy leads to the consideration of systems that bridge the gap between focusing and interferometry. X-ray diffractive Axicons and PFLs are shown to be limiting cases of a family of designs that are the X-ray equivalents of "Axilenses", offering different combinations of effective area and bandpass. It is shown that linear gratings can be used as diffractive alternatives to the grazing incidence mirror "periscopes" that have been investigated as beam combiners in an interferometer. The gratings form achromatic fringes in a process related to the Talbot effect. The results of simulations and of a laboratory demonstration-of-principle experiment are presented.

Laue lenses are an emerging technology based on diffraction in crystals that allows the concentration of soft gamma rays. This kind of optics that works in the 100 keV - 1.5 MeV band can be used to realize an highsensitivity and high-angular resolution telescope (in a narrow field of view). This paper reviews the recent progresses that have been done in the development of efficient crystals, in the design study and in the modelisation of the answer of Laue lenses. Through the example of a new concept of 20 m focal length lens focusing in the 100 keV - 600 keV band, the performance of a telescope based on a Laue lens is presented. This lens, uses the most efficient mosaic crystals in each sub-energy range in order to yield the maximum reflectivity. Imaging capabilities are investigated and shows promising results.

In a Laue lens a large number of crystals are disposed on concentric rings such as they diffract via Braggdiffraction the incident gamma-rays onto a common focal spot. Compact structured high-Z mosaic-crystals are among the most efficient diffraction media for the domain of nuclear astrophysics (i.e. 300 keV ≤ E ≤ 1.5 MeV). We have studied the potential of various high-Z crystals such as Ir, W, Au, Ag, Pt, Rh and AsGa for a Laue lens application. The diffraction performance of gold, silver and platinum crystals have been measured during runs at the European Synchrotron Radiation Facility and in a reactor-beamline at the Institut Laue Langevin, Grenoble in France. Several of the tested high-Z materials show outstanding performances with reflectivities reaching the theoretical limits for mosaic-crystals, and hence open the way towards efficient focusing optics at MeV energies.

We report on new results on the development activity of broad band Laue lenses for hard X-/gamma-ray astronomy (70/100-600 keV). After the development of a first prototype, whose performance was presented at the SPIE conference on Astronomical Telescopes held last year in Marseille (Frontera et al. 2008), we have improved the lens assembling technology. We present the the development status of the new lens prototype that is on the way to be assembled.

The NuSTAR (Nuclear Spectroscopy Telescope Array) observatory (Harrison et al. 2009), expected to be launched into an equatorial low earth orbit in 2011, will have two mirror assemblies capable of imaging X-rays in the hard X-ray band between 5 keV and 80 keV. It will be the first X-ray observatory using multilayer coatings to significantly expand the bandwidth of the typical X-ray telescope of 0.1 keV to 10 keV. The mirror assemblies use a segmented design to simplify the construction process, as such they require 4,680 mirror substrates coated with appropriately designed multilayers to enhance reflectivity for hard X-rays. These substrates are produced by slumping commercially available thin glass sheets. In this paper we report on our work of manufacturing these substrates at NASA Goddard Space Flight Center.

As for all space missions, the limit imposed on the payload mass budget by the launcher is the main driver that forces the use of very lightweight optics. Considering the International X-ray Observatory (IXO) mission the present configuration has a mirror collecting area in the order of 3 m² at 1.25 keV, 0.65 m² at 6 keV, and 150 cm² at 30 keV. These large collecting areas could be obtained with a mirror assembly composed of a large number of high quality glass segments each being able to deliver the required angular resolution better or equal to 5 arcsec. These segments will form a X-Ray Optical Unit (XOU), an optical subunit of the telescope, and the XOUs will be assembled to form the whole mirror system. Based on the INAF-OAB experience in the thermal slumping of thin glass optics, a possible approach for the realization of large size and lightweight X-ray mirrors is described in this paper. Moulds made in a suitable material (as for example Silicon Carbide or Fused Silica) and having the suitable (parabolic and hyperbolic) profile are used for the realization of thin glass Mirror Plates (MP), with dimensions in the range of 200- 400 mm. After a thermal cycle the slumped MPs are characterized for acceptation and handled by means of an active support using vacuum suction for the integration phase. In this phase an active optical feedback is used to ensure the correct alignment of the MPs within the XOU. The MPs are then glued in its proper position in the XOU using also suitable glass ribs for the stiffening of the whole module. An investigation in the problems and possible solutions to the slumping, measurement, integration and testing of the glass MPs into the XOU will be given, particularly with respect to a XOU scaled prototype that will be manufactured and used to assess the technology.

The International X-ray Observatory mission is a collaborative effort of NASA, ESA, and JAXA. It will have unprecedented capabilities in spectroscopy, imaging, timing and polarization measurement. A key enabling element of the mission is a flight mirror assembly providing unprecedented large effective area (3 m²) and high angular resolution of (5 arcseconds half-power diameter). In this paper we outline the conceptual design of the mirror assembly and development of technology to enable its construction.

We present an overview update of the metrologic approach to be employed for the segmented mirror fabrication for the IXO soft 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 metrology equipment are in hand but that a number of the needed quantities remain too uncertain relative to mission requirements. This is driven by the mounting of the mirrors themselves. We then discuss some plans for addressing the mirror mounting issues. Finally, we also briefly discuss some promising mandrel metrology techniques.

We report on the continuation of the development of test samples of astronomical x-ray optics based on thermally formed glass foils and on bent Si wafers. Experiments with thermal glass forming have continued adding wider range of evaluated and optimized parameters including viscosity and internal stress analyses, as well as investigation of mounting influences. Experiments with Si wafers focused on their quality improvements such as flatness and thickness uniformity in order to better meet the requirements of future X-ray astronomy projects applications, as well as on study of their surface quality, defects analysis, and methods for its reproducible measurement.

Future X-ray astrophysics missions, such as the International X-ray Observatory, IXO, require the development of novel optics in order to deliver the mission's large aperture, high angular resolution and low mass requirements. A series of activities have been pursued by ESA, leading a consortium of European industries to develop Silicon Pore Optics for use as an x-ray mirror technology. A novel process takes as the base mirror material commercially available silicon wafers, which have been shown to possess excellent x-ray reflecting qualities. These are ribbed, curved and stacked concentrically in layers that have the desired shape at a given radii of the x-ray aperture. Pairs of stacks are aligned and mounted into doubly reflecting mirror modules that can be aligned into the x-ray aperture without the very high angular and position alignment requirements that need to be achieved for mirror plates within the mirror module. The use of this silicon pore optics design substantially reduces mirror assembly time, equipment and costs in comparison to alternative IXO mirror designs. This paper will report the current technology development status of the silicon pore optics and the roadmap expected for developments to meet an IXO schedule. Test results from measurements performed at the PTB lab of the Bessy synchrotron facility and from full illumination at the Panter x-ray facility will be presented.

Silicon pore optics are currently under development for missions such as the International X-ray Observatory (IXO) as an alternative to the glass or nickel shell mirrors that were used in previous generation X-ray telescopes. The unprecedented effective area requirement of the IXO requires a modular optics design suitable for mass production. In this paper we discuss the current state-of-the-art in plate manufacturing technology. We provide examples of process innovations that have directly impacted the cost per mirror plate and have reduced the manufacturing cost of a mirror module. We show how a switch from silicon to silica as the reflective surface results in a simplified process flow without a corresponding change in the optical performance. We demonstrate how standard photolithographic techniques, applied in the semiconductor industry, can be used to pattern a reflective layer. The 5 arc-second angular resolution requirement of the IXO has stimulated a theoretical analysis of engineering tolerances in relation to angular resolution. We prove that improved control of the wedge angle by means of etch rate monitoring results in improved angular resolution. The results of this investigation will be used as the basis for future development in design for mass production.

The ESA's invitation to participate in the innovative technology developments for the new space mission represents the natural continuation of the efforts of the Czech team in development of innovative X-ray telescopes, focusing on particular demands and requirements of a concrete project, with emphasis on fully new and light-weight technologies. In this paper we focus on studying of other alternative materials such as SiC or glassy carbon, which could be considered as suitable materials for the producing of precise light weight X-ray optics due to their physical and chemical properties and so far successfully compete with more common materials (like glass or Si) as well as on Si wafers with improved surface quality and analysis and evaluation of measured data.

High throughput lightweight Hard X-ray Optics manufactured via electroforming replication process from supersmooth mandrels are the primary candidate for some of future New Hard X-ray missions. Media Lario Technologies (MLT) is the industrial enabler exploiting the electroforming technology initially applied for the ESA XMM-Newton mission and further developed in cooperation with Brera Astronomical Observatory (INAF/OAB). The current and ongoing development activities in Media Lario Technologies complement the electroforming technology with a suite of critical manufacturing and assembly of the Mirror Module Unit. In this paper, the progress on mandrels manufacturing, mirror shell replication, multilayer coating deposition, mirror module integration, and relevant metrology is reported in view of the upcoming production phase. Mandrel production is a key point in terms of performances and schedule; the results from of NiP prototype mandrels fabricated using a proprietary multistep surface finishing process are reported. The progress in the replication of ultrathin Nickel and Nickel-Cobalt substrates gold coated mirror shells is reported together with the results of MLT Magnetron Sputtering multilayer coating technology for the hard x-ray waveband and its application to W/Si. Due to the criticality of low thickness mirror handling, the integration concept has been refined and tested on prototype mechanical structures under full illumination UV vertical optical bench.

Focusing mirrors manufactured via galvanic replication process from negative shape mandrels is the candidate solution for some of next future X-ray missions. Media Lario Technologies (MLT) is the industrial enabler developing, in collaboration with Brera Astronomical Observatory (INAF/OAB), the Optical Payload for future Hard X-ray mission. Concerning mandrel technology, MLT is engaged in a development programme aiming at improving the mandrels performance and their production rate. The angular resolution and the reflectivity of the mirrors replicated from the mandrels are strongly dependent on the mandrel performances and their stability. High throughput X-ray missions, require the massive production of mandrels in a short time, with angular resolution better than 7 arcsec Half Energy Width (HEW) and a surface micro-roughness in the order of 0.3 nm RMS. In order to achieve these results, several technological aspects are under investigation using a proprietary multistep surface finishing process. In particular, the metrology and the estimated optical performances of the mandrel are computed by means of dedicated post-processing and herein reported. Microroughness, medium scale errors, azimuthal slope error, axial slope errors, and mechanical dimensions are the quantities that have been measured by using atomic force microscope, high resolution optical profiler, contactless rotondimeter and high accuracy axial profilometer.

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

We have fabricated a precision full-cylinder stainless-steel mandrel at NASA Marshall Space Flight Center. The mandrel is figured for a 30-cm-diameter primary (paraboloid) mirror of an 840-cm focal-length Wolter-1 telescope. We have developed this mandrel for experiments in slumping-thermal forming at about 600°C-of glass mirror segments at NASA Goddard Space Flight Center, in support of NASA's participation in the International X-ray Observatory (IXO). Precision turning of stainless-steel mandrels may offer a low-cost alternative to conventional figuring of fusedsilica or other glassy forming mandrels. We report on the fabrication, metrology, and performance of this first mandrel; then we discuss plans and goals for stainless-steel mandrel technology.

Future X-ray observatory missions require grazing-incidence X-ray optics with angular resolution of < 5 arcsec half power diameter. For X-ray mirrors fabricated using replication processes, the achievable resolution depends ultimately on the quality of the polished replication mandrels. With an aim to fabricate better mirror shells, and also to reduce the cost/time of mandrel production, a computer-controlled machine is being developed for deterministic and localized polishing of mandrels. A key component in this is software that predicts the surface residual errors under a given set of operating parameters and lap configuration. Design considerations of the polishing lap are discussed and the effects of nonconformance of the lap and the mandrel are presented.

In the last decade Very High Energy (VHE) gamma-ray astronomy has improved rapidly opening a new window for ground-based astronomy with surprising implications in the theoretical models. Nowadays, it is possible to make imaging, photometry and spectroscopy of sources with good sensitivity and angular resolution using new facilities as MAGIC, HESS and VERITAS. The latest results of astronomy in the TeV band obtained using such facilities demonstrate the essential role of this window for high energy astrophysics. For this reason new projects (e.g. CTA and AGIS) have been started with the aim to increase the sensitivity and expand the energy band coverage. For such telescopes arrays probably tens of thousands of optical mirror panels must be manufactured with an adequate industrial process, then tested and mounted into the telescopes. Because of the high number of mirrors it is mandatory to perform feasibility studies to test various techniques to meet the technical and cost-effectiveness requirements for the next generation TeV telescopes as CTA and AGIS. In this context at the Astronomical Observatory of Brera (INAF-OAB) we have started the investigation of different techniques for the manufacturing of stiff and lightweight optical glass mirror panels. These panels show a sandwich-like structure with two thin glass skins on both sides, the reflective one being optically shaped using an ad-hoc slumping procedure. The technologies here presented can be addressed both for primary or secondary mirrors for the next generation of Cherenkov telescopes. In this paper we present and discuss the different techniques we are investigating with some preliminary results obtained from test panels realized.

The Cherenkov Telescope Array (CTA), currently in its early design phase, is a proposed new project for groundbased gamma-ray astronomy with at least 10 times higher sensitivity than current instruments. CTA is planned to consist of several tens of large Imaging Atmospheric Cherenkov Telescopes (IACTs) with a combined reflective surface of up to 10,000 m². The challenge for the future CTA array is to develop lightweight and cost efficient mirrors with high production rates, good longterm durability and adequate optical properties. The technologies currently under investigation comprise different methods of carbon fibre/epoxy based substrates, sandwich concepts with cold-slumped surfaces made of thin float glass and different structural materials like aluminum honeycomb, glass foam or PU foam inside, and aluminum sandwich structures with either diamond milled surfaces or reflective foils. The current status of the mirror development for CTA will be summarized together with investigations on the improvement of the reflective surfaces and their protection against degradation.

For the International X-ray observatory (IXO), a mirror module with an effective area of 3 m² at 1.25 keV and at least 0.65 m² at 6 keV has to be realized. To achieve this goal, coated silicon pore optics has been developed over the last years. One of the challenges is to coat the Si plates and still to realize Si-Si bonding. It has been demonstrated that ribbed silicon plates can be produced and assembled into stacks. All previously work has been done using uncoated Si plates. In this paper we describe how to coat the ribbed Si plates with an Ir coating and a top C coating through a mask so that there will be coating only between the ribs and not in the area where bonding takes place. The paper includes description of the mounting jig and how to align the mask on top of the plate. We will also present energy scans from Si plates coated through a mask.

We have investigated the performance, structure and stability of periodic multilayer films containing silicon carbide (SiC) and aluminum (Al) layers designed for use as reflective coatings in the extreme ultraviolet (EUV). We find that SiC/Al multilayers prepared by magnetron sputtering have low stress, good temporal and thermal stability, and provide good performance in the EUV, particularly for applications requiring a narrow spectral bandpass such as monochromatic solar imaging. Transmission electron microscopy reveals amorphous SiC layers and polycrystalline Al layers having a strong <111> texture, and relatively large roughness associated with the Al crystallites. Fits to EUV reflectance measurements also indicate large interface widths, consistent with the electron microscopy results. SiC/Al multilayers deposited by reactive sputtering with nitrogen comprise Al layers that are nearly amorphous and considerably smoother than films deposited non-reactively, but no improvements in EUV reflectance were obtained.

We have used reactive sputtering with nitrogen to deposit both periodic and depth-graded Co/C X-ray multilayers intended for use at grazing incidence for astronomical applications. In comparison to Co/C films deposited nonreactively, reactively-sputtered films show lower stress and lower roughness. Consequently we have been able to fabricate Co/C multilayers that have much smaller periods relative to what can be achieved using non-reactive sputtering. We have thus far produced several prototype Co/C multilayers, including a depth-graded film containing 500 bilayers for use below 10 keV, and a depth-graded film containing 1100 bilayers for use up to 100 keV. Both of these films show excellent X-ray performance, low film stress, and excellent temporal stability.

The Nuclear Spectroscopic Telescope Array, NuSTAR, is a NASA funded Small Explorer Mission, SMEX, scheduled for launch in mid 2011. The spacecraft will fly two co-aligned conical approximation Wolter-I optics with a focal length of 10 meters. The mirrors will be deposited with Pt/SiC and W/Si multilayers to provide a broad band reflectivity from 6 keV up to 78.4 keV. To optimize the mirror coating we use a Figure of Merit procedure developed for gazing incidence optics, which averages the effective area over the energy range, and combines an energy weighting function with an angular weighting function to control the shape of the desired effective area. The NuSTAR multilayers are depth graded with a power-law, di = a/(b + i)^c, and we optimize over the total number of bi-layers, N, c, and the maximum bi-layer thickness, dmax. The result is a 10 mirror group design optimized for a flat even energy response both on and off-axis.

The design of the next generation of hard-X-ray focusing telescopes requires highly optimized reflecting coatings, with the maximum efficiency over a broad energy band and a relatively large field of view. Multilayer coatings based on layer thicknesses with power-law distribution are often considered as a convenient solution to achieve angular and energetic broad band reflection of X-ray at grazing incidence, being also particularly suitable for numerical optimization. In this work we consider the optimization of the telescope for the New Hard X-ray Mission, an Italian project based on four optical modules with multilayer-coated Nickel-replicated Wolter optics, able to focus high-energy X-ray radiation (up to 80 keV) with good imaging resolution (20 arcsec HEW). The optimization of the telescope was studied from the point of view of shell sizes, coating materials and multilayer structures. In particular, the best structure of the coating is determined by means of numerical optimization methods introducing also the number of layers as optimization parameters. Very effective solutions are found even with a low number of bilayers (~100).

Mandrel replication by Nickel electroforming is a well-suited process to manufacture X-ray mirrors, making use of Gold layer playing the twofold role of release agent and reflective coating. To increase the optical performances of mirrors it is crucial to minimize the impact of X-ray scattering effects related to surface microroughness, especially when the mirror is intended to operate in hard X-rays. In this case, the Gold layer simply acts as release agent because the reflection is demanded to interferential over-coatings. Even though the replicated optical surface is usually believed to reproduce the smooth topography of the master, a surface degradation is commonly observed. Such a worsening can also suffer from a contribution from the spontaneous roughness growth of the Gold layer itself: if this is the case, the mirror's optical quality could potentially benefit from the utilization of a thin Gold layer (< 100 nm) instead of the traditional thick gold layer (> 100 nm). To prove the effectiveness of the Gold thickness reduction, a microroughness characterization of replicated thin gold layers has been achieved. We report here a preliminary roughness study of 3 electroformed Ni samples replicated from a super-polished Zerodur flat master with various Gold layer thicknesses, in the spectral range 0.02-1000 μm. The study is organized as follows: (a) characterization of the 3 replicated samples; (b) comparison of the Gold roughness for thin vs. thick layers; (c) comparison of the two sides of Gold layers.

A differential deposition technique is being developed to correct the low- and mid-spatial-frequency deviations in the axial figure profile of Wolter-type grazing-incidence X-ray optics. These deviations arise due to various factors in the fabrication process and they degrade the performance of optics by limiting the achievable angular resolution. In the differential deposition technique, material is selectively deposited in varying thickness along the length of the optic to minimize these deviations, thereby improving the overall figure. The process is being tested on focusing X-ray optics being developed at MSFC for small-animal radionuclide imaging. The required spatial resolution for these optics is 100 μm (30 arc secs), which can be achieved with the electroformnickel- replication fabrication technique regularly employed at MSFC. However, by improving the figure quality of the optics through differential deposition, we aim to significantly improve the resolution beyond this value.

Silicon pore optics is a technology developed to enable future large area X-ray telescopes, such as the International Xray Observatory (IXO), a candidate mission in the ESA Space Science Programme 'Cosmic Visions 2015-2025'. IXO uses nested mirrors in Wolter-I configuration to focus grazing incidence X-ray photons on a detector plane. The IXO mirrors will have to meet stringent performance requirements including an effective area of ~3 m² at 1.25 keV and ~1 m² at 6 keV and angular resolution better than 5 arc seconds. To achieve the collecting area requires a total polished mirror surface area of ~1300 m² with a surface roughness better than 0.5 nm rms. By using commercial high-quality 12" silicon wafers which are diced, structured, wedged, coated, bent and stacked the stringent performance requirements of IXO can be attained without any costly polishing steps. Two of these stacks are then assembled into a co-aligned mirror module, which is a complete X-ray imaging system. Included in the mirror module are the isostatic mounting points, providing a reliable interface to the telescope. Hundreds of such mirror modules are finally integrated into petals, and mounted onto the spacecraft to form an X-ray optic of four meters in diameter. In this paper we will present the silicon pore optics assembly process and latest X-ray results. The required metrology is described in detail and experimental methods are shown, which allow to assess the quality of the HPOs during production and to predict the performance when measured in synchrotron radiation facilities.

X-rays at various energies can be focussed with reflective optics at grazing incidence with a well-known reflectivity achieving a high effective area by means of various designs. On XMM the high collecting area was achieved by means of thin mirror shells which were made by nickel replication combining the parabola and hyperbola sections according to the WOLTER I design in a single element. 58 of these "elements" were combined to build a mirror assembly with an effective area of 1450 cm2 @1.5 keV per mirror assembly. In order to achieve a higher effective area for IXO the density needs to be reduced. This could be achieved by pore optics elements integrated into a set of 8 petals made of Cesic® as an optical bench. This design is fitting into the fairing of Ariane with a diameter of 4.2 m and achieves an effective area of 3.36 m². It will withstand the high launch loads of up to 60 g and provide a negligible degradation to the optical performance due to thermal loads and gravitational relaxation. The design, including the interfaces to the telescope and to the pore optics, will be presented.

The necessity to reduce the mass and to increase the collecting area requires that the thickness of the optics becomes more and more thinner. Simbol-X was a typical example of this trend. Such thickness makes the shells floppy and therefore unable to maintain the correct shape. During the integration of the shells into the mechanical structure, only negligible deformation must be introduced. The low thickness means also that the shells must be glued on both sides to reach a good stiffness of the whole mirror module and this fact introduces a set of mounting problems. In INAF - Osservatorio Astronomico di Brera an integration process has been developed. The use of stiffening rings and of a temporary structure is the key to maintain the right shape of the shell. In this article the results of the integration of the first three prototypes of the Simbol-X optics are presented. The description of the process and the analysis of the degradation of the performances during the integration are shown in detail.

The telescope on the International X-ray Observatory (IXO) comprises nearly 15 thousand thin glass mirror segments, each of them is capable of reflecting board-band soft x-rays at grazing angles. These mirror segments form densely packed, two-staged shells, in a Wolter type I optical design, in which each pair of the mirrors focus x-ray onto the focal plane in two reflections. The requirement in angular resolution of the IXO telescope is 5 arc-seconds. This requirement places severe challenges in forming precisely shaped mirror segments as well as in aligning and mounting these thin mirrors, which are 200 to 400 mm in size and 0.4 mm in thickness. In this paper, we will describe an approach for aligning and mounting the IXO mirror segments, in which no active adjustment is made to correct for any existing figure errors. The approach comprises processes such as suspension of a mirror under gravity to minimize gravity distortion, temporary bonding onto a strongback, alignment and transfer to a permanent structure and release of mirror from the temporary mount. Experimental results and analysis in this development are reported.

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.

The Smart X-ray Optics project is a UK based consortium of six institutions investigating active/adaptive X-ray optics for both large and small scale applications. The large scale application is aimed towards future high angular resolution, large X-ray telescopes for X-ray astronomy. The work presented here includes the modelling and the testing of the large scale prototype optic. The prototype incorporates piezoelectric devices to a standard X-ray shell to enable the surface to be actively deformed, aiming to achieve an angular resolution better than that currently available (e.g. Chandra 0.5"). The initial design is based on a thin nickel ellipsoid segment on the back of which a series of piezoelectric actuators have been bonded. Results from the initial testing of this prototype in the X-ray beam line at the University of Leicester are presented and simulation of the X-ray performance, the effect of the actuated piezoelectric devices on the detected image and further models are discussed.

The next generation of X-ray telescopes will require both high resolution and high sensitivity to target the earliest astronomical objects, to this end the UK based Smart X-ray Optics (SXO) project has been investigating the application of active/adaptive optics to traditional grazing incidence X-ray optics and this has resulted in the fabrication and testing of our first active X-ray prototype in November 2008. Results from these initial tests have proved very encouraging for this advancing technology and have highlighted the prototype's ability to deform its optical surface through piezoelectric actuation. We present a critical analysis of the first prototype system, discussing metrology of the mandrel, the nickel replicated ellipsoidal optics and the prototype. The measured actuator influence functions of the prototype are compared against finite element analysis simulations and the observed characteristics are then described. The advances required in the current technology are then outlined in relation to a second generation of active X-ray prototype, which is scheduled for X-ray testing in 2010.

We report an experimental result 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 mirror. Both are coated by Mo/Si multilayer. The diameter of the primary and the secondary mirrors are 80 mm and 55mm, respectively. The secondary mirror is a deformable mirror with 31 bimorph-piezo electrodes. The EUV from a laser plasma source was exposed to a Ni mesh with 31 micro-m wires. The image of this mesh was obtained by a backilluminated CCD. The reference wave was made by an optical laser source with 1 μm pin-hole. We measure the wave form of this reference wave and control the secondary mirror to get a good EUV image. Since the paths of EUV and the optical light for the reference were different from each other, we modify the target wave from to control the deformable mirror, as the EUV image is best. The higher order Zernike components of the target wave form, as well as the tilts and focus components, were added to the reference wave form made by simply calculated. We confirmed the validity of this control and performed a 2.1 arc-sec resolution.

The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer (SMEX) mission which employs two focusing optics. The optics are composed of stacks of thin mirror shells and spacers. Epoxy is used to bond the mirror shells to the spacers and is a crucial component in determining the structural and optical performance of the telescopes. We describe the epoxy selection for NuSTAR optics, emphasizing those epoxy characteristics essential to obtaining good optical performance.

We have developed a simulation tool for a Wolter I telescope subject to deformations. The aim is to understand and predict the behavior of Simbol-X and other future missions (NuSTAR, Astro-H, IXO, ...). Our code, based on Monte-Carlo ray-tracing, computes the full photon trajectories up to the detector plane, along with the deformations. The degradation of the imaging system is corrected using metrology. This tool allows to perform many analyzes in order to optimize the configuration of any of these telescopes.

Focusing X-ray telescopes with imaging capabilities, like SIMBOL-X, HEXISAT and IXO, are characterized by very long focal lengths, greater than 10m. The constraints posed by the launchers on the maximum dimensions of a payload, make necessary using alternatives to monolithic telescopes. One possibility is that the mirror and the detectors are carried by two separate spacecrafts that fly in formation. Another is placing the detector module on a bench that will be extended once in final orbit. In both the case the system will be subjected to deformation due the relative movement of the mirrors with respect to detectors. In one case the deformation will be due to the correction on the position and attitude of the detector spacecraft to maintain the formation with the mirror spacecraft, while in the other to oscillations of the detectors on the top of the bench. The aim of this work is to compare the behavior of the system in the two different configurations and to evaluate the performances of the on board metrology systems needed not to degrade the telescope angular resolution.

The International X-ray Observatory (IXO) is a very ambitious mission, aimed at the X-ray observation of the early Universe. This makes IXO extremely demanding in terms of effective area and angular resolution. In particular, the HEW requirement below 10 keV is 5 arcsec Half-Energy Width (HEW). At higher photon energies, the HEW is expected to increase, and the angular resolution to be correspondingly degraded, due to the increasing relevance of the X-ray scattering off the reflecting surfaces. Therefore, the HEW up to 40 keV is required to be better than 30 arcsec, even though the IXO goal is to achieve an angular resolution as close as possible to 5 arcsec also at this energy. To this end, the roughness of the reflecting surfaces has to not exceed a tolerance, expressed in terms of a surface roughness PSD (Power-Spectral-Density). In this work we provide such tolerances by simulating the HEW scattering term for IXO, assuming a specific configuration for the optical module and different hypotheses on the PSD of mirrors.