Evaluation of characteristics of Hamamatsu low-gain avalanche detectors

Low-gain avalanche detectors (LGADs) are attractive because of their fast response to realize a 4-dimensional (4D) tracker in future experiments in high energy physics and other applications. We fabricated LGAD diodes and strip sensors. Their responses before and after irradiation to gamma rays or neutrons were evaluated with light-emitting diodes (LEDs) of various wave lengths and with an infrared laser. The sensors showed a gain of more than 10 before irradiation. Little reduction of gain was observed with gamma irradiation. A substantial reduction of gain was observed after neutron irradiation. A gain increase observed in the interstrip region after neutron irradiation, whereas the gain was equal to one before irradiation.