Energy Resolution Contributions in Reach-Through Avalanche Photodiodes

Avalanche photodiodes (APD) are used in the muonic helium Lamb shift experiment for detection of 8 keV X-rays. Reach-through APDs from Hamamatsu Photonics have been investigated for X-ray detection as alternative to conventional APDs. In order to evaluate the different contributions to the energy resolution obtained in a reach-through APD, its response to both 8 keV X-rays and visible light pulses was investigated. The intrinsic resolution was estimated by further measurements of the electronic noise contribution and the gain non-uniformity was assessed. The excess noise factor was determined. Results at different temperatures are presented.