Studies of operation modes for the ATHENA WFI detectors

The Wide Field Imager (WFI) is one of two instruments for ESA’s Athena X-ray observatory. It will employ DEPFET (depleted p-channel field effect transistor) active pixel technology to provide unprecedented spectroscopic and imaging capabilities over a broad energy band from 0.2 keV to 15 keV, with a large field of view of 40′ × 40′ . Using prototype detectors of various sizes we have started first tests of window mode operation, where only a subset of the full sensor array is being read out, leading to a higher frame rate for this area. We also investigated the possibility of operation at room temperature for a basic functionality test when cooling is not possible, e.g. on ground after integration on the satellite.