A Time Projection Chamber with triple GEM and pixel readout

Abstract

Due to many favorable properties it is very attractive to use Micro Pattern Gas Detectors (MPGDs) as gas amplification stages in Time Projection Chambers (TPCs). Especially the high granularity, intrinsic suppression of ion backflow, high rate capability and almost no distortions due to E × B effects are desirable in future particle physics detectors. To fully exploit the potential of combining MPGDs and TPCs the pad size in the readout plane should be adapted to the structure size of the gas amplification stage. The Timepix chip is well suited for the use as readout chip in gaseous detector by providing metalized pads to pick up the charge. We have constructed a test chamber with a triple GEM and Timepix readout and a maximum drift distance of 26 cm. With this setup we have studied the performance of the detector in various operation environments. Different setups for tests with cosmic rays and for tests in high magnetic fields have been realized. In these environments key detector parameters such as spatial resolution have been studied in dependence on different gas mixtures. We have seen strong evidence for observation of individual electrons and a spatial resolution of down to 80 μm has been measured.