Reach-through APDs for X-ray detection

The performance of two reach-through avalanche photodiodes (RT-APD) manufactured by Hamamatsu Photonics with different active areas, 5×5 and 3×5 mm², has been investigated. In order to evaluate their suitability for the muonic helium Lamb shift experiment already being prepared. The gain was determined as a function of voltage and temperature for the 5×5 RT-APD prototype. The gain non-linearity between X-rays and light was found to be as high as 15% for the 5×5 prototype and 20% for the 3×5 prototype for gains between 70 and 200 at 20 °C. The energy resolution and the minimum detectable energy (MDE) were also determined. The best energy resolution obtained for 8 keV X-rays was 9.3% for a gain of 30 at −20 °C. The MDE achieved was 0.2 keV obtained for a gain of 100 and for a temperature of −20 °C.