Gaseous detectors with micropattern gas amplification stages and CMOS pixel chip readout

Gas Electron Multipliers (GEMs) and Micromegas have demonstrated a very good performance in many applications. In particular, the spatial resolution has improved significantly compared to wire-based gaseous detectors. Because of the small pitch between the sensitive areas of gas amplification the limiting factor is usually given by the readout structure. To fully exploit the benefits of MPGDs we used a Timepix chip, a CMOS pixel chip with a pixel pitch of 55 mu m, in combination with a GEM stack or aMicromegas realized as an InGrid structure. Both combinations have been tested in a time projection chamber (TPC) with a maximum drift distance of 26 cm. Additionally, various pad sizes have been studied with the GEM setup to investigate their influence on several key parameters. Also, first measurements of an InGrid based X-ray detector are described. In particular, measurements of background events were performed to evaluate a possible application of the detector in low rate dark matter searches.