A prototype Si/CdTe Compton camera and the polarization measurement

A Compton camera is the most promising approach for gamma-ray detection in the energy region from several hundred kiloelectronvolts to megaelectronvolts, especially for application in high energy astrophysics. In order to obtain good angular resolution, semiconductor detectors such as silicon, germanium and cadmium telluride(CdTe) have several advantages over scintillation detectors, which have been used so far. Based on the recent advances of high resolution CdTe and silicon imaging detectors, we are working on a Si/CdTe Compton camera. We have developed 64-pixel CdTe detectors with a pixel size of 2 mm × 2 mm and double- sided Si strip detectors(DSSDs) with a position resolution of 800 μm. As a prototype Si/CdTe Compton camera, we use a DSSD as a scatterer and two CdTe pixel detectors as an absorber. In order to verify its performance, we irradiate the camera with 100% linearly polarized 170 keV γ-rays and demonstrate the system works properly as a Compton camera. The resolution of the reconstructed scattering angle is 22°(full-width at half-maximum). Measurement of polarization is also reported. The polarimetric modulation factor is obtained to be 43%, which is consistent with the prediction of Monte Carlo simulations.