DEPFET based focal plane instrumentation for X-ray imaging spectroscopy in space

Abstract

The combined Detector-Amplifier structure DEPFET (Depleted P-channel FET) is a promising new building block for large area silicon detector devices, e.g. in X-ray astronomy and high energy physics. The DEPFET structure combines excellent energy resolution, high speed readout and low power consumption with the attractive features of random accessibility of pixels and on-demand readout. In addition, it features all advantages of a sideways depleted device in terms of fill factor and quantum efficiency. Finally, the newly introduced combination of a DEPFET structure and a silicon drift diode (SDD) like drift ring structure to form a so-called macropixel device allows for large flexibility in terms of pixel size. Presently, focal plane instrumentation for X-ray imaging spectroscopy based on DEPFET arrays is being developed for a variety of space experiments with very different requirements. The next European X-ray Observatory XEUS is going to have a wide field imager covering the full FOV, which consists of a large-area DEPFET array. The concept for the French-Italian X-ray Astronomy mission SIMBOL-X includes a focal plane array based on DEPFET macropixels, and, finally, the MIXS (Mercury Imaging X-ray Spectrometer) instrument on the European Mercury exploration mission BepiColombo also contains two DEPFET macropixel based focal plane arrays. While for XEUS and SIMBOL-X excellent energy resolution and quantum efficiency in the low energy range are mandatory, radiation hardness is imperative for MIXS. A first production of DEPFET prototype arrays showed very promising results. More sophisticated prototype devices for SIMBOL-X and XEUS with a large sensitive area as well as flight grade devices for the MIXS instrument have been produced at the MPI semiconductor laboratory in Munich/Germany. The strategies to meet the respective requirements by an appropriate design of the focal plane instrumentation are shown as well as first results of the new production.