X-ray Based Methods for 3D Characterization of Charge Collection and Homogeneity of Sensors with the Use of Timepix Chip

AbstraktAbstract

Timepix is a universal readout chip for pixel detectors which can be connected to various semiconductor sensors. The device has a 256x256 matrix of square pixels with a pitch of 55 µm. Every single pixel is able to measure the collected charge. The traditional material used for sensors is monocrystalline silicon (Si). However, other materials such as gallium arsenide (GaAs) or cadmium telluride (CdTe) are applicable as well. To describe the properties of the sensors it is important to probe and evaluate the charge collection efficiency and its homogeneity across sensor area (or if possible even in its volume). A probing technique utilizing X-ray radiation applicable for different sensor materials has been designed. A collimated narrow line beam is applied to perform the 3D characterization of the sensor volume. When the parallel beam hits the sensor at small angles it penetrates the adjacent pixels at different but known depths. This technique enables us to record the charge collection efficiency for different depths in hit pixels. By scanning the beam over the detector area we can characterize all pixels at all depths. In this work we present the 3D charge collection efficiency maps obtained with several sensors: Si (300 μm), GaAs (300μm) and CdTe (1000 μm).

Timepix is a universal readout chip for pixel detectors which can be connected to various semiconductor sensors. The device has a 256x256 matrix of square pixels with a pitch of 55 µm. Every single pixel is able to measure the collected charge. The traditional material used for sensors is monocrystalline silicon (Si). However, other materials such as gallium arsenide (GaAs) or cadmium telluride (CdTe) are applicable as well. To describe the properties of the sensors it is important to probe and evaluate the charge collection efficiency and its homogeneity across sensor area (or if possible even in its volume). A probing technique utilizing X-ray radiation applicable for different sensor materials has been designed. A collimated narrow line beam is applied to perform the 3D characterization of the sensor volume. When the parallel beam hits the sensor at small angles it penetrates the adjacent pixels at different but known depths. This technique enables us to record the charge collection efficiency for different depths in hit pixels. By scanning the beam over the detector area we can characterize all pixels at all depths. In this work we present the 3D charge collection efficiency maps obtained with several sensors: Si (300 μm), GaAs (300μm) and CdTe (1000 μm).