DEPFET Macropixel detectors, based on the fusion of the combined Detector-Amplifier structure DEPFET with
a silicon drift chamber (SDD) like drift ring structure, combine the excellent properties of the DEPFETs with
the advantages of the drift detectors. As both device concepts rely on the principle of sideways depletion, a
device entrance window with excellent properties is obtained at full depletion of the detector volume.
DEPFET based focal plane arrays have been proposed for the Focal Plane Detectors for the MIXS (Mercury
Imaging X-ray Spectrometer) instrument on BepiColombo, ESAs fifth cornerstone mission, with destination
Mercury. MIXS uses a lightweight Wolter Type 1 mirror system to focus fluorescent radiation from the Mercury
surface on the FPA detector, which yields the spatially resolved relative element abundance in Mercurys crust.
In combination with the reference information from the Solar Intensity X-ray Spectrometer (SIXS), the element
abundance can be measured quantitatively as well. The FPA needs to have an energy resolution better than
200 eV FWHM @ 1 keV and is required to cover an energy range from 0.5 keV to 10 keV, for a pixel size of
300 x 300 μm2. Main challenges for the instrument are the increase in leakage current due to a high level of
radiation damage, and the limited cooling resources due to the difficult thermal environment in the mercury
orbit. By applying an advanced cooling concept, using all available cooling power for the detector itself, and
very high speed readout, the energy resolution requirement can be kept during the entire mission lifetime up to
an end-of-life dose of ~ 3 × 1010 10 MeV p / cm2. The production of the first batch of flight devices has been
finished at the MPI semiconductor laboratory, and first prototype modules have been built. The results of the
first tests will be presented here.