Charge protection characterisation and drift time resolution improvement for GridPix

A GridPix detector is a gaseous detector capable of detecting single primary electrons from ionising particles. Such a detector consists of a pixel chip as active anode covered with a thin layer of silicon rich silicon nitride (SiRN) for protection against discharges. A layer of 8 JlIl1 SiRN, and according recent tests even 4 JlIl1, is sufficient to protect against discharges. The effect of the thickness of the SiRN layer on the operation of a detector has been determined. Time walk effects due to pixel electronics response time and gas gain statistics cause errors in drift time measurements thereby worsening the resolution in the drift direction. Simulations and measurements have been performed to determine how much time walk can be compensated for. GridPix detectors are high resolution low mass detectors that measures track segments in 3D. Very recently we performed first tests in a 250 Me V proton beam, in order to investigate the application of GridPix in Proton therapy and results are promising