Speaker
Description
The Hyper-Kamiokande experiment aims at various physics research, such as discoveries of the leptonic CP violation and proton decays, using a large water Cherenkov detector. Toward the operation from 2027, a delivery of 50cm diameter photomultiplier tubes (PMTs), Hamamatsu R12860 PMT, is ongoing. We started long-term measurements stably to monitor the quality during the production, where 16 PMTs can be evaluated at once. Due to the large aperture of the PMT, the performance is sensitive to the geomagnetic field. In order to suppress the geomagnetism, a μ-metal shield was attached to each PMT instead of geomagnetic compensation coils planned in Hyper-Kamiokande. Because a residual magnetic field varies at each PMT position in the long-term measurement, I studied the impact on the PMT performance.
I will report the impact on the collection efficiency of the PMT using magnetic field compensation coils along three axes where the magnetic field is applied up to about 1000mG. The signal and dark count rates were taken using laser light pulses. I developed a model based on the relationship between the collection efficiency and the magnetic field in three axes. It can correct the varied performance by a different magnetic field at the long-term measurement.
