Characterization of the Detector Response to Electrons of Silicon Drift Detectors for the TRISTAN Project

Abstract: Right-handed neutrinos are a natural extension of the Standard Model of particle physics. Such particles would only interact through the mixing with the left-handed neutrinos, hence they are called sterile neutrinos. If their mass were in the keV-range they would be Dark Matter candidates. By investigating the electron spectrum of the tritium beta-decay the parameter space with masses up to the endpoint of 18.6 keV can be probed. A sterile neutrino manifests as a kink-like structure in the spectrum. To achieve this goal the TRISTAN project develops a new detector system for the KATRIN experiment that can search for these new particles using the silicon drift detector technology. One major effect on the performance of the detectors is the so called dead layer. Here, a new characterization method for the prototype detectors is presented using the Kr-83m decay conversion electrons. By tilting the detector its effective dead layer increases, which leads to different peak positions. The difference of peak positions between two tilting angles is independent of source effects and is thus suitable for characterization.A dead layer is then extracted by comparing the measurements to Monte-Carlo simulations. A dead layer in the order of 50 nm was found.