A. Inneman

Advanced x-ray optics with Si wafers and slumped glass

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.

Recent progress with x-ray optics based on Si wafers and glass foils

We report on recent progress with development 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. Recent efforts with Si wafers have been 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. The role of substrates quality in performance of final mirror arrays, as required by large future space X-ray astronomy experiments was also studied. The problem of increasing size of Si wafers, required for some X-ray optics applications, is also addressed. First results of irradiation tests of selected substrates are also reported and discussed.

Novel x-ray optics with Si wafers and formed glass

The thermally formed thin glass foils and optically shaped Si wafers are considered to belong to the most promising technologies for future large space X-ray telescopes. We present and discuss the recent progress in these technologies, as well as properties of test mirrors produced and tested. For both technologies, both flat and curved samples have been produced and tested. The achieved profile accuracy is of order of 1 micrometer or better, while the bending technologies maintain the intrinsic fine surface microroughness of substrates (better than 0.5 nm for glass and around 0.1 nm for Si wafers).

Novel technologies for x-ray multi-foil optics

The future large space X-ray telescopes in study (such as the ESAs XEUS) require novel approaches and innovative lightweight technologies. Although there are several alternative possibilities, in general the shaped thin glass foils and shaped Si wafers are considered to belong to the most promising ones. We present and discuss the recent progress in these technologies, as well as properties of test mirrors produced and tested. For both technologies, both flat and curved samples have been produced and tested. The achieved profile accuracy is of order of 1 micrometer or better, while the bending technologies maintain the intrinsic fine surface microroughness of substrates (better than 0.5 nm).

X-ray Lobster Eye all-sky monitor for rocket experiment

This paper presents a Lobster Eye (LE) X-ray telescope developed for the Water Recovery X-ray Rocket (WRX-R) experiment. The primary payload of the rocket experiment is a soft X-ray spectroscope developed by the Pennsylvania State University (PSU), USA. The Czech team participates by hard LE X-ray telescope as a secondary payload. The astrophysical objective of the rocket experiment is the Vela Supernova of size about 8deg x 8deg. In the center of the nebula is a neutron star with a strong magnetic field, roughly the mass of the Sun and a diameter of about 20 kilometers forming the Vela pulsar. The primary objective of WRX-R is the spectral measurement of the outer part of the nebula in soft X-ray and FOV of 3.25deg x 3.25deg. The secondary objective (hard LE X-ray telescope) is the Vela neutron star observation. The hard LE telescope consists of two X-ray telescopes with the Timepix detector. First telescope uses 2D LE Schmidt optics (2DLE- REX) with focal length over 1m and 4 Timepix detectors (2x2 matrix). The telescope FOV is 1.5deg x 1.5deg with spectral range from 3keV to 60keV. The second telescope uses 1D LE Schmidt optics (1D-LE-REX) with focal length of 25 cm and one Timepix detector. The telescope is made as a wide field with FOV 4.5deg x 3.5deg and spectral range from 3keV to 40keV. The rocket experiment serves as a technology demonstration mission for the payloads. The LE X-ray telescopes can be in the future used as all‐sky monitor/surveyor. The astrophysical observation can cover the hard X-ray observation of astrophysical sources in time-domain, the GRBs surveying or the exploration of the gravitational wave sources.

Slumping monitoring of glass and silicone foils for x-ray space telescopes

We developed a non-contact method for in-situ monitoring of the thermal slumping of glass and silicone foils to optimize this technology for the production of high quality mirrors for large aperture x-ray space telescopes. The telescopes crucial part is a high throughput, heavily nested mirror array with the angular resolution better than 5 arcsec. Its construction requires precise and light-weight segmented optics with surface micro-roughness on the order of 0.1 nm. Promising materials are glass or silicon foils shaped by thermal forming. The desired parameters can be achieved only through optimizing the slumping process. We monitored the slumping by taking the snapshots of the shapes every five minutes at constant temperature and the final shapes we measured with the Taylor Hobson profilometer. The shapes were parabolic and the deviations from a circle had the peak-to-valley values of 20-30 μm. The observed hot plastic deformation of the foils was controlled by viscous flow. We calculated and plotted the relations between the middle part deflection, viscosity, and heat-treatment time. These relations have been utilized for the development of a numerical model enabling computer simulation. By the simulation, we verify the materials properties and generate new data for the thorough optimization of the slumping process.

Lobster eye: technology and imaging properties

Lobster eye optics, as a wide field of view imaging system, is perfectly suited for x-ray astronomy but can be useful also in the lab. This paper presents a brief overview of the technologies developed in our group, where the glass and silicon mirrors are used to built up the Schmidt lobster eye design and mainly discuss the mirror design consequences on the resulting imaging properties of the system. Corrections of various image distortions and imperfections, either geometric, spectral or temporal in case of scanning observations have to be applied in order to get a valuable instrument. Several image processing methods are discussed and its strengths and weaknesses are shown for both astronomy and laboratory experiments.

Applications of lobster eye optics

Applications of wide field Lobster Eye X ray telescopes are presented and discussed. The wide field X ray optics was originally proposed for use in X-ray astronomy, but there are numerous other application areas as well.

Design of novel x-ray optical system for rocket experiment

A novel design of X-ray optical system - concentrator for astrophysical rocket experiment is investigated. The proposed system is based on four modules with Kirkpatrick-Baez (KB) configuration allowing usage of multi-foil mirrors arranged to parabolic profile. The KB modules are supplemented by rotationally symmetrical parabolic segments. This X-ray optical system effectively uses a circular aperture. The KB modules are placed in four quadrants while the segments are set into a Cartesian cross between the KB modules. Studied optical system is under consideration for the student rocket experiment of University of Colorado that should verify function of NIST’s energy-dispersive detector based on Transition Edge Sensors (TES microcalorimeters).

Full-aperture X-ray tests of Kirkpatrick-Baez modules: preliminary results

We report on preliminary results of full aperture X-ray optical tests at the X-ray test facility at the University of Colorado (USA) of four test modules of Kirkpatrick-Baez (KB) X-ray optical systems performed in August 2010. Direct experimental comparisons were made between gold-coated optics of two novel substrates: glass foils and silicon wafers. The preliminary results are promising, with full-width half-maxima of full stacks being of order of 30 arcsec in 2D full arrangement. These results justify further efforts to improve KB optics for use in low-cost, high-performance space-borne astronomical imaging instruments for X-ray wavelengths.