Dead-time investigation of SiPMs for application at pulsed muon sources

Until recently a photomultiplier tube (PMT) was the only viable option for photon detection on μSR instruments [1]. A PMT is well suited to this application, as it offers fast rise time, small dead-time (~15ns) and an excellent spectral match to the scintillator emission. They are also low-noise devices and are relatively inexpensive. However, the PMT has certain limitations, such as a strong sensitivity to magnetic fields, prompting this search for new technologies. Specific requirements depend on the measurement technique, the SiSR instrument, and the type of muon source being used. For example, the PSI high field instrument has successfully implemented siliconphotomultiplier technology (SiPM) to construct compact, field-insensitive, fast timing detectors [2]. At PSI the beam timing structure is `continuous' meaning that there is effectively only one muon being measured at a time, negating the need for high count rate capability. While SiPM technology has been used very successfully at the PSI continuous muon source, benefits at a pulsed muon source have yet to be realized.