High Resolution Non Dispersive X-Ray Spectroscopy with State of the Art Silicon Detectors

Abstract

For the European X-ray Multi-Mirror mission (XMM) and the German X-ray satellite ABRIXAS fully depleted pn-CCDs have been fabricated, enabling high speed, low noise, position resolving X-ray spectroscopy. The detector was designed and fabricated with a homogeneously sensitive area of 36 cm². At 150 K it has a noise of 5e^- rms only, with a readout time for the total focal plane array of 4 ms. The maximum count rate for single photon counting is 100,000 cps under flat field conditions. Its position resolution is in the order of 100 µm. The quantum efficiency is higher than 90% from carbon K X-rays (272 eV) up to 10keV. In addition, new cylindrical silicon drift detectors have been designed, fabricated and tested. They comprise an integrated on-chip amplifier system with continuous reset, on-chip voltage divider, electron accumulation layer stabilizer, large area, homogeneous radiation entrance window and a drain for surface generated leakage current. At count rates as high as 1,000,000 counts per sec and per cm², they still show excellent spectroscopic behaviour at room temperature operation.

These detector systems were developed for X-ray astronomy, synchrotron light sources and for X-ray fluorescence analysis applications. All systems are fabricated in planar technology having the detector and amplifiers monolithically integrated on high resistivity silicon.