H. Otono

A Pixelized Photon Detector (PPD) is a generic name for the semiconductor devices operated in the Geiger-mode, such as Silicon PhotoMultiplier and Multi-Pixel Photon Counter, which has high photon counting capability. While the internal mechanisms of the PPD have been intensively studied in recent years, the existing models do not include the avalanche process. We have simulated the multiplication and quenching of the avalanche process and have succeeded in reproducing the output waveform of the PPD. Furthermore our model predicts the existence of dead-time in the PPD which has never been numerically predicted. For serching the dead-time, we also have developed waveform analysis method using deconvolution which has the potential to distinguish neibouring pulses precisely. In this paper, we discuss our improved model and waveform analysis method.

In the 1990s, a novel semiconductor photon-sensor operated in Geiger-mode was invented in Russia (Silicon PhotoMultiplier), which consists of many tiny pixels and has a single photon level sensitivity. Since then, various types of the sensor with this scheme, Pixelized Photon Detectors (PPD), have been developed in many places in the world. For instance, Hamamatsu Photonics K.K. in Japan produces the PPD as a Multi-Pixel Photon Counter. While the internal mechanisms of the PPD have been intensively studied in recent years, the existing models do not succeeded to fully reproduce the output characteristic, such as waveforms at low temperature. We have developed a new model with the transient multiplication and quenching of the realistic avalanche process and have succeeded in reproducing the output waveform of the PPD at various temperature. In this paper, we discuss our improved model.

Study of afterpulsing events gives us an information of recovery time of Multi-Pixel Photon Counter (MPPC), which can be obtained by measuring the amplitude and the time interval between an afterpulse and its original pulse. It is important to measure the recovery time for investigating the internal mechanism of MPPC and to design detectors with this device. We have developed a waveform-analysis method to discriminate the pulses. As a result, recovery time and its bias dependency were obtained for three different types of MPPC.