Dieter Pauschinger

Hard x-ray mirror fabrication capabilities in Europe

The new properties of third-generation synchrotron radiation beams call for corresponding progress in instrumentation technology. This is particularly true for hard x-ray mirrors, for which new technologies have been implemented to meet outstanding requirements. The transfer of experience from other fields such as high-energy lasers and astronomy has been of major importance in the realization of new designs. The European Synchrotron Radiation Facility, the first third-generation hard x-ray source in Europe, has stimulated R&D programs of four European companies in the field of hard x-ray mirrors. This paper presents the major achievements of these companies.

Optical performance prediction of thin-walled Wolter type I mirror shells for x-rays in the 1- to 8-keV energy range

The study predicts, on the basis of surface topology measurements, the optical performance of thin-walled Wolter type 1 mirror shells over the specified energy range of the XMM telescope (0.3-8 keV). To analyze the effect of deformations which can be treated by geometrical optics, a Monte Carlo code was developed which uses a 3D model of the telescope to trace individual rays through the telescope. The computed point spread functions are found to be in excellent agreement with the ones measured in a full-aperture test at 1.5 keV X-ray energy. At 8 keV, a loss in optical performance was observed. A comparison of the surface data with mirrors that performed efficiently at 8 keV showed deformations with spatial wavelengths below 1 mm to be responsible for the degradation at 8 keV X-ray energy. It is concluded that in the transition region between Rayleigh limit and smooth surface limit, approximate optical predictions can be achieved by applying geometrical optics.

Development and production of lightweight CFRP carriers for the XMM telescope x-ray mirrors

The European Space Agencys 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.

Optical demonstration model for the XMM telescope based on lightweight CFRP/EPOXY x-ray mirrors

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.

Production of thin-walled lightweight CFRP/EPOXY x-ray mirrors for the XMM telescope

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.

Plane grating monochromator system SX700 High Flux: design principle and first results

The x-ray monochromator SX700 High Flux design is based on the successful basic SX700 system which is installed in various beam lines. It consists of a rotatable plane tilting mirror, a rotatable plane grating, and a fixed ellipsoidal focusing mirror. By using two different gratings, the SX700 covers the energy range from 5 eV to 2800 eV. Together with the control software it is possible to move the tilting mirror together with the rotating grating continuously in such a way that a fixed source focus is achieved over a wide energy range (from 38 eV to 2800 eV for 1220 l/mm and from 11.4 eV to 860 eV for 366 l/mm). The most recent software update now includes any user defined angle relation between mirror and grating. To withstand the high heat loads of synchrotron beams without any compromise in optical performance, the SX700 monochromator was upgraded. This is achieved by a proper material selection for the optical components (plane mirror and grating) and by the installation of a respective cooling system for these components. In this paper the development of the chosen design solution and first beam line results are reported.

Assembly, performance prediction, and x-ray test of the optical demonstration model (ODM) for the x-ray telescope XMM

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.