Energy resolution contributions in reach-through avalanche photodiodes

Avalanche photodiodes (APDs) will be used in the muonic helium Lamb shift experiment for detection of 8 keV X-rays. Reach-through APDs (RT-APDs) from Hamamatsu Photonics have been investigated for X-ray detection as an alternative to conventional APDs. In order to understand the behavior of the energy resolution obtained in a RT-APD for 8 keV X-rays, the APD response to visible light pulses from a LED has also been investigated. The gain non-uniformity is determined from the comparison of the energy resolution obtained for X-rays and light pulses. In addition, the measurement of the electronic noise contribution allows the determination of the excess noise factor. Results at different temperatures are shown.