Characterizing Gain Suppression in Low-Gain Avalanche Detectors

Low-gain avalanche detectors (LGADs) are thin silicon detectors with a highly doped gain layer. They offer excellent detection efficiency for low ionizing particles. However, gain suppression has been observed corresponding to larger charge deposits, leading to lower signal amplification and angle dependency of the sensor’s response. In order to better characterize this mechanism, we studied 4 LGAD sensors from the Fundazione Bruno Kessler (FBK) of varying thicknesses. By using the Tandem Van de Graaff accelerator of the Center for Experimental Nuclear Physics and Astrophysics (CENPA) at the University of Washington, a proton beam was generated to create charge deposits at the MeV scale within the detectors. The gain was measured for different bias voltages, proton angle of incidence, and energy deposit size. These results are of particular interest to PIONEER, a next generation pion decay experiment. PIONEER anticipates charge deposits over a large scale (keV to MeV); LGADs are a potential detector for PIONEER, thus making it imperative to understand the gain suppression mechanism. In my poster, I will present the results of the 2024 beam campaign, and how they will benefit the PIONEER experiment.