A Method to Detect Charge Sharing Using Pulse Shape of CdTe Detector

X-ray spectral information is important for X-ray imaging. However, under high dose such as medical CT, pile-up is a problem and correct measurement is difficult. One effective measure is to reduce the detector area, but as the electrodes become smaller, charge-sharing becomes a problem. Different charge-sharing measures are taken by different methods depending on the electrode structure. If only the measurement of the X-ray spectrum at a single point, for example, a detector with a structure of a single pixel and an auxiliary electrode for charge-sharing correction around it can be considered. Such a simple structure allows independent measurement and analysis of output waveforms at all electrodes. When there is a large difference in the mobility of electron and hole such as in Cadmium Telluride (CdTe), pulses that are positively or negatively different from the normal waveform (negative pulses) may be generated depending on the position where the electron-hole pairs occur in the detector. This event includes a charge-sharing event. Therefore, detecting and removing this event can reduce the effects of charge-sharing. Two electrodes of the same size (3mm*1.45mm) were mounted on CdTe for confirmation, and spectrum and signals were measured with a digital MCA and an oscilloscope. As a result, it was confirmed that negative pulses sometimes occur at the same time as normal signals and that the energy resolution of the spectrum can be improved by removing events that occur at the same time as the negative pulses.