[B._Beckhoff,_et_al.]_Handbook_of_Practical_X-Ray_(b-ok.org).pdf

Xmm was launched from kourou in french guiana on

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XMM was launched from Kourou in French-Guiana on December 10, 1999. Commissioning of the scientific payload was completed in the middle of March 2000. In this overview, the basic instrument features as measured on ground and in orbit will be shown. The Concept of Fully Depleted, Back Illuminated, Radiation Hard pn-CCDs For ESA’s XMM mission, we have developed a 6 × 6 cm 2 large monolithic X-ray CCD [76] with high detection efficiency up to 15 keV, low noise level (ENC 5e (rms) at an operating temperature of 90 C) and an ultrafast readout time of 4.6 ms per 3 × 1 cm 2 large subunit (see Figs. 4.45 and 4.50). A schematic cross-section, already showing some of the advantages of the concept, is displayed in Fig. 4.44. The pn-CCD concept and the fabrication technology allow for an opti- mum adaption of the pixel size to the X-ray optics, varying from 30 µ m up to 300 µ m pixel size. Up to now systems with 50–200 µ m have been produced. The XMM telescope performance of 13 arcsec half energy width (HEW) translates
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X-Ray Detectors and XRF Detection Channels 265 p + Transfer direction + p + p + p + On-chip amplifier (40 cm) W p + p f 3 f 2 f 1 285 m m 12 m m Signal charge n + anode Depletion voltage Entrance window ( p + back diode) Potential minimum Electron potential - Fully depleted detector volume (n-Si, 2 - 5 k W cm) n - epitaxial layer Detector depth Pulses for signal transfer Fig. 4.44. A schematic cross-section through the pn-CCD along a transfer channel. The device is back illuminated and fully depleted over 300 µ m thickness. The electron potential perpendicular to the wafer surface is shown on the right-hand side to 470 µ m position resolution in the focal plane. The FWHM of the point spread function (PSF) is about 7 arcsec. A pixel size of 150 µ m × 150 µ m was chosen, giving a position resolution of 120 µ m, resulting in an equiv- alent spatial resolving capability of 3 . 3 arcsec. This is sufficient to fully conserve the positional information of the X-rays from the mirrors. The energy response is higher than 90% at 10 keV because of the sensitive thickness of 300 µ m according to the wafer thickness. The low energy response is given by the very shallow implant of the p + back contact; the effective “dead” layer is smaller than 200 ˚ A [77]. The excellent time resolution is achieved by the parallel readout of 64 channels per subunit, 768 channels for the entire cam- era. A high radiation hardness is built in by avoiding active MOS structures and by the fast transfer of the charge in a depth of more than 10 µ m. The spatially uniform detector quality over the entire field of view is realized by the monolithic fabrication of the pn-CCD on a single wafer. For redundancy reasons, 12 individually operated 3 × 1 cm 2 large pn-CCDs subunits were defined. Inhomogeneities were not observed over the entire sensitive area in the calibration energy band from 0.5 keV up to 8 keV, within the precision of the measurements limited by Poisson statistics. The insensitive gap in the vertical separation of the pn-CCDs is about 40 µ m, neighboring CCDs in
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