Speaker
Description
The Aerogel Ring Imaging CHerenkov (ARICH) counter of the Belle II spectrometer performs particle identification by detecting Cherenkov ring images from the aerogel radiator using Hybrid Avalanche Photo Detectors (HAPDs). Belle II will operate into the 2040s targeting 50 /ab integrated luminosity. To support extended operation and improve particle identification efficiency, an ARICH upgrade is planned during the long shutdown in the early 2030s.
HAPDs are expected to perform well for about 10 years despite radiation damage but are not suited for longer-term use, and their production has ended. Therefore, we are evaluating alternative photodetectors, such as Multi-Pixel Photon Counters (MPPCs) and Large Area Picosecond Photo Detectors (LAPPDs), for their tolerance to magnetic fields and to high levels of neutron irradiation.
Various MPPC types from Hamamatsu Photonics were assessed, particularly for operation under Belle II’s high-background environment, which increases dark pulses. We irradiated samples and tested them under cooling and annealing, both of which significantly reduced dark count rates. We developed a dedicated readout ASIC, “TF01A64,” for MPPCs and evaluated its performance using MPPC signals. A 64-channel readout system incorporating TF01A64 was constructed, and its basic functionality was confirmed in preparation for an upcoming beam test using Cherenkov ring imaging at an electron beam facility.
LAPPDs from Incom are also under evaluation. Their performance was tested with a TOFPET2 ASIC-based readout, and we are developing a system compatible with LAPPDs for further testing with particle beams and in magnetic fields.
In this presentation, we will introduce the ARICH upgrade plan and report the status of the photodetector and readout system developments toward upcoming beam and magnetic field tests.
