In our ongoing studies of high precision glass slumping we have successfully formed the first Wolter-I X-ray mirror
segments with parabola and hyperbola in one piece. It could be demonstrated that the excellent surface roughness of the
0.55 mm thick display glass chosen is conserved during the slumping process. The influence of several parameters of the
process, such as maximum temperature, heating and cooling rates etc. have to be measured and controlled with adequate
metrology. Currently, we are optimizing the process to reduce the figure errors down to 1 micrometer what will be the
starting point for further, final figure error corrections. We point out that metrology plays an important role in achieving a
high precision optics, i.e. an angular resolution of a few arcsec. In this paper we report on the results of our studies and
discuss them in the context of the requirements for future X-ray telescopes with large apertures.
Future X-ray missions are aiming at large mirror collecting areas of the order of several square meters. This is obtained with mirror assemblies composed of a large number of segments. The angular resolution of each one must be measured separately down to 1 arcsec. The mass limits imposed by the launchers require low weight and high stiffness materials. In this context we have focused our recent studies on the manufacturing of thin glass mirror segments. These mirrors are made from sheet glass which can be shaped in a high-precision slumping process to e.g. a Wolter-I figure. The excellent surface roughness of the sheet glass chosen is conserved during the slumping process and the final figure corrections with non-contacting tools. The influence of several parameters of the process, such as glass and mould material, heating and cooling, has been measured and controlled with adequate metrology. In this paper we describe our current efforts which are aiming at the production of a Wolter-I scaled demonstration model - preferentially with parabola and hyperbola in one piece - made of thin sheet glass.
Next generation lithography is likely to deploy extreme UV (EUV) light at 13.5 nm wavelength for key manufacturing processes. Currently, all promising EUV light source concepts require efficient light collection optics in order to deliver sufficeintly high light power for profitable chip production. With densely nested Wolter-Type 1 reflective optics we designed, and fabricated such optics. In this paper we report on the latest achievements in design, development and on our first at wavelength testing results of such collection optics.
KEYWORDS: Cameras, Mirrors, Charge-coupled devices, Telescopes, X-rays, Sensors, CCD cameras, Galaxy groups and clusters, Electronics, Digital signal processing
What is the nature of the Dark Energy that is driving the universe apart? Clusters of galaxies offer an ideal probe of cosmology because they are the best tracers of Dark Matter and their distribution on very large scales which is dominated by the Dark Energy. DUO will measure 10.000 clusters of galaxies, the power spectrum of density fluctuations of clusters and their number density as a function of cosmic time. Although designed long before the existence of Dark Energy was claimed, the ABRIXAS type X-ray telescope turns out to be ideally suited for this task: DUO is, in essence, a re-flight of the ABRIXAS X-ray telescope which some modifications of the focal plane instrumentation. First of all, we will use new CCDs which are improved versions of the pn-CCDs successfully flown on XMM-Newton. A modular concept having seven individual cameras in the foci of the seven mirror systems allows us to design the orientation of the seven telescopes with respect to each other matching the scientific needs of the DUO mission. Details of the concept including mechanical, electrical and thermal aspects are given.
Constellation-X, NASA's next major X-ray observatory, is planned to be launched in 2012/2013. Each of the four identical spacecraft contains a large diameter, spectroscopic X-ray telescope (SXT). The mirror assembly is compsed of many densely nested Wolter type 1 mirror reflectors, having segment angles of 30 or 60 degrees. The reflectors will be made of thin, accurately shaped glass sheets, onto which the reflective mirror surface is replicated from high precision, super polished Zerodur mandrels.
One key issue for high-performance mirrors is the exact shape of the glass substrates. They are produced at NASA/GSFC by a dedicated hot forming process (slumping) from precision forming mandrels. The hot forming process requires special materials for the glass substrates and the forming mandrels.
In this paper we report on figuring (precision machining), polishing, metrology and performance analyses of Wolter type 1 forming mandrels. The mandrels are characterized by the following features:
Mandrel dimensions: 450 x 640 mm2; radius of curvature: ~800 mm; segment angle: ~40 deg; shape: hyperboloid or paraboloid; material: Zerodur K20 (Keatite) or fused silica (quartz).
Dark Energy dominates the mass-energy content of the universe (about 73%) but we do not understand it. Most of the remainder of the Universe consists of Dark Matter (23%), made of an unknown particle. The problem of the origin of Dark Energy has become the biggest problem in astrophysics and one of the biggest problems in all of science. The major extant X-ray observatories, the Chandra X-ray Observatory and XMM-Newton, do not have the ability to perform large-area surveys of the sky. But Dark Energy is smoothly distributed throughout the universe and the whole universe is needed to study it. There are two basic methods to explore the properties of Dark Energy, viz. geometrical tests (supernovae) and studies of the way in which Dark Energy has influenced the large scale structure of the universe and its evolution. DUO will use the latter method, employing the copious X-ray emission from clusters of galaxies. Clusters of galaxies offer an ideal probe of cosmology because they are the best tracers of Dark Matter and their distribution on very large scales is dominated by the Dark Energy. In order to take the next step in understanding Dark Energy, viz. the measurement of the 'equation of state' parameter 'w', an X-ray telescope following the design of ABRIXAS will be accommodated into a Small Explorer mission in lowearth orbit. The telescope will perform a scan of 6,000 sq. degs. in the area of sky covered by the Sloan Digital Sky Survey (North), together with a deeper, smaller survey in the Southern hemisphere. DUO will detect 10.000 clusters of galaxies, measure the number density of clusters as a function of cosmic time, and the power spectrum of density fluctuations out to a redshift exceeding one. When combined with the spectrum of density fluctuations in the Cosmic Microwave Background from a redshift of 1100, this will provide a powerful lever arm for the crucial measurement of cosmological parameters.
Wilhelm Egle, Wolfgang Hafner, Axel Matthes, Eral Erzin, Bernhard Gaenswein, Herbert Schwarz, Piotr Marczuk, Martin Antoni, Wolfgang Singer, Frank Melzer, Joachim Hainz
EUV sources are designed to emit radiation around 13.5 nm wavelength into a solid angle of up to 2π sr. With a suitable Wolter type 1 grazing incidence optic such EUV photons can be collected with high efficiency and focussed onto a preferred target. Such Wolter type 1 collectors are characterized by densely nested concentric and confocal mirror shells with fixed distance from the source and the intermediate image.
In this paper we will report on optical and mechanical design, development, fabrication and testing of nested Wolter type 1 collectors, capable of collecting and imaging EUV photons at 13.5 nm wavelength with high efficiency.
The radiation emitted from an EUV source is collected and focused by a suitable collector system. A reflective blazed grating is used in -1st diffraction order to select a definite spectral band around 13.5 nm wavelength from the broad-band emission spectrum of the source. The effective grating area is segmented into a set of different plane gratings, mounted on a common base plate. In order to focus the light from the collector system, the grating segments are tilted and form a best-fit polygon surface. A specific groove density variation on the grating segments significantly improves the imaging performance. In this paper, we report on design, fabrication and testing of the grating system.
ESA's XEUS x-ray telescope design asks for segmented Wolter 1 mirror plates with radii up to 5 m and a focal length of 50 m. The mirror plates shall have an excellent optical performance (< 5 arcsec HEW). They shall be made by metal (e.g. Nickel) electroforming. This design approach requires highest quality segmented Wolter 1 mandrel plates, with an on-axis HEW < 2 arcsec and a micro-roughness better than 0.3 nm (rms). We will report about the novel design concept, fabrication approach and verification of the x-ray optical performance of the first XEUS demonstration mandrel.
Since 1974 X-ray optics and optical ground support equipment for various national and international X-ray and EUV- missions have been designed, manufactured, tested and delivered by Carl Zeiss/Oberkochen. The range of X-ray optics includes mirror systems for ASTRO 8, ROSAT and ABRIXAS, as well as mandrels for SAX, JET-X, WFXT, XMM, Constellation-X and XEUS. An example for high quality EUV- systems is the Wolter II mirror system for SOHO-CDS. We will give a retrospect to previous programs, report about recently performed and finished X-ray optics, as well as we will give an outlook for future contributions.
Two identical Wolter type 1 mandrels, with 50 cm diameter and 8.4 meter focal length, to be used by NASA/MSFC for their Constellation-X mirror development program, have been produced and tested by Carl Zeiss. In August 1999, both mandrels have been delivered to MSFC. Key optical performance of both mandrels: On-axis HEW; < 3.2 arc sec and micro-roughness: better than 0.30 nm RMS. We will report about mandrels design, fabrication, test and verification of their X-ray optical performance.
At the July 1998 SPIE Conference, we reported about design and development as well as about fabrication, optical testing and integration of the grazing incidence ABRIXAS mirrors. In this paper we will describe the environmental and x-ray optical testing of the seven flight mirror modules and we will report about their achieved performance.
ABRIXAS stands for 'A Broadband Imaging X-ray All-Sky Survey'. Its launch is scheduled for spring 1999, it shall perform, thanks to its special design, an efficient all-sky survey at high photon energies, thus continuing ROSATs successful work in an extended energy band. We will report here about the design and development activities for the ABRIXAS Mirror System.
The tight ABRIXAS program schedule requires 250 mirror shells to be produced, checked and accepted within one year. This means that the fabrication processes have to be fully understood and kept completely under control. This applies mainly for the major production steps, like gold-coating of the mandrels, Nickel electroforming, mirror shells release from the mandrels and mirror shells testing and acceptance. We will report about the way how we tackled these technical and logistic challenges. Another important step for the optical performance of ABRIXAS Mirror Modules is the integration of the 27 mirror shells in the structural parts. This process requires high skill and good control means, like optical collimator, CCD camera and sophisticated analysis tools in order to achieve optimal-co-alignment of the 27 mirror shells axes and best confocality. This is guaranteed by dedicated test-facilities and sophisticated analyses software. We will report about the results obtained on integrated single mirrors shells as well as on the assembly of all 27 mirror shells.
Each of the three mirror modules of the XMM Wolter-I-type telescope is composed of 58 nested mirror shells. The smallest gap between two adjacent mirror shells measures only 1.6 mm. The fixation and alignment concept has been qualified with the Optical Demonstration Model ODM, which consists of four CFRP mirrors. It has the same entrance diameter (700 mm) as the flight model. The 3D topology of the mirrors was determined for spatial wavelengths ranging from 3 micrometers to 550 mm by three measuring devices. The optical quality of the mirror shells as a function of x-ray energy was predicted by a code developed at Zeiss. During integration roundness and alignment of the mirrors were monitored by a full-aperture Hartmann-type test with visible light. The entire model and single mirrors have been x-ray tested at the MPE long beam facility at photon energies up to 8 KeV. The results of x-ray tests and performance predictions are compared and discussed.
The European Space Agency's high throughput X-ray Telescope XMM (X-ray Multi Mirror Mission) has three modules each consisting of 58 highly nested monolithic Wolter I mirrors. The mirrors have diameters in the range between 300 and 700 mm, an axial length of 600 mm and a focal length of 7.5 m. Due to the high packing density within the mirror module the mirror shells have to be sufficiently thin, and due to the high number of mirrors the shells have to be as light as possible. In order to meet these requirements Carl Zeiss and Dornier have developed the CFRP/EPOXY mirror shell technology under ESA contract. In this paper the development and production of carriers of various sizes will be reported. It will be shown that the CFRP laminate with the lay-up chosen by Dornier is a good substrate for the replication of x-ray mirror shells.
The ESA High Throughput X-ray Spectroscopy Mission (XMM) is a telescope with three modules each consisting of 58 highly nested Wolter I mirrors with a focal length of 7.5 m. Envisaged resolution for an XMM module is 27 arcsec Half Energy Width at 8 keV x-ray energy. Due to the high packing density of the mirror shells within such a telescope, thin walled and light weight mirrors are required. In this paper the results of production, integration and performance tests of XMM CRFP/EPOXY mirror shells of all sizes (diameters from 300 mm to 700 mm; length equals 600 mm; wall thickness from 0.7 mm to 1.3 mm) for the XMM telescope will be reported.
Attention is given to the ESA High Throughput X-ray Spectroscopy Mission (XMM), a telescope with three modules each consisting of 58 highly nested Wolter I mirrors with a focal length of 7.5 m. The envisaged resolution for an XMM module is 27 arcsec half energy width (HEW) at 8 keV X-ray energy. Results are presented of production and performance tests of the medium-size XMM CFRP/EPOXY mirror shell, including: the production of CFRP carriers as the mirror shell substrate with a global ovality PTV(R) of less than 50 microns and HEW contribution due to roundness of less than 10 arcsec; the replication of Wolter I shaped reflecting gold surface on the CFRP substrate; the measurement of optical performance (HEW is less than 17 arcsec at 1.5 keV X-ray energy); and an investigation of long-term stability for the 10-yr mission time. It is shown that the CFRP/EPOXY mirror shell replication technology can meet the XMM mission requirements.
A large number of mirror shells are required for the European Space Agency's XMM telescope three mirror modules, each of which consists of 58 thin walled highly nested Wolter I mirrors. The specified performance of the XMM mirror modules requires new design concepts and application of new technologies for the production of the lightweight mirror shells. Under an ESA contract, Carl Zeiss is leading a European industrial/scientific consortium to develop technologies that allow production of real size XMM mirror shells by a dedicated metal/epoxy resin
replication technique. In late 1988 the first full size XMM mirror shell was successfully replicated, having the following characteristics: total length
600 mm, maximum shell diameter 400 mm, carrier material/thickness graphite-epoxy/0.8 mm, replication layers gold/epoxy, and total replicated mirror surface 7500 cm2. The development, preparation, and mirror shell replication are described, and the first results of the performance of the mirror shell after measurements and x-ray testing are presented.
The design concept of the mirrors for the European Space Agency's high throughput x-ray spectroscopy mission XMM is characterized by thin (1 mm) graphite epoxy shells as the mirror structure and a replication technique to produce the mirror surface. The mirror microroughness is specified to r 0.5 nm (rms); profile errors should not exceed 2.5 arcsec. An ESA research study has been performed by Carl Zeiss
and subcontractors (Dornier GmbH, Max Planck Institut für Extraterrestrische Physik/Garching, University of Leicester, X-ray Astronomical Group, Dept. of Physics) to clarify whether graphite epoxy mirror structures are able to meet the tight XMM mirror figuring and surface requirements and to determine what measures have to be taken to overcome the typical
problems associated with composite materials used as mirror substrates, such as print-through of fibers and inner structure, short term/long term
stability, and water absorption and outgassing. The starting conditions and progress during development are described. The present status of optical and x-ray performance of replicated flat graphite epoxy mirrors is reported, and aspects for further improvement of graphite epoxy mirrors is discussed.
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