DEPFET macropixel arrays as focal plane instrumentation for SIMBOL-X and MIXS on BepiColombo

Abstract

Focal plane instrumentation based on the combined Detector-Amplifier structure DEPFET (Depleted P-channel FET) are being considered for the application in a large variety of experiments in X-ray astronomy and high energy physics. DEPFET based detectors show excellent energy resolution and can be read out at high speed. In addition, they combine low power consumption with the attractive features of random accessibility of pixels and on-demand readout. They feature all advantages of a sideways depleted device in terms of fill factor and quantum efficiency, and so-called macropixel devices, being a combination of a DEPFET with a drift ring structure, allow for large flexibility in terms of pixel size. Presently, DEPFET based focal plane instrumentation for X-ray imaging spectroscopy is being developed for a variety of space experiments with very different requirements. The payload of the French-Italian X-ray Astronomy mission SIMBOL-X includes a focal plane array based on DEPFET macropixels, and one of the instruments on board the European Mercury exploration mission BepiColombo, the so-called MIXS (Mercury Imaging X-ray Spectrometer) instrument, also uses DEPFET macropixel based focal plane arrays for the detection of X-rays. In both cases, the performance of the respective X-ray optics demands the use of macropixel matrices due to the large required pixel sizes. The MPI semiconductor laboratory in Munich has produced prototype devices for SIMBOL-X with a large sensitive area as well as the first flight grade devices for the MIXS instrument; and the first large-area detectors have been tested. The devices show excellent performance in terms of energy resolution, peak-to-background ratio and homogeneity. Here, the requirements of the respective experiments on their detectors are outlined, together with the strategies to comply with the requirements by choosing a suitable readout strategy and an appropriate design of the focal plane instrumentation. Finally, the first test results of the large area macropixel prototype devices are shown.