The new versatile general purpose surface-muon instrument (GPS) based on silicon photomultipliers for ${\mu}$SR measurements on a continuous-wave beam

摘要

We report on the design and commissioning of a new spectrometer for muon-spinrelaxation/rotation studies installed at the Swiss Muon Source (S$\mu$S) of thePaul Scherrer Institute (PSI, Switzerland). This new instrument is essentiallya new design and replaces the old general-purpose surface-muon instrument (GPS)which has been for long the workhorse of the $\mu$SR user facility at PSI. Bymaking use of muon and positron detectors made of plastic scintillators readout by silicon photomultipliers (SiPMs), a time resolution of the completeinstrument of about 160 ps (standard deviation) could be achieved. In addition,the absence of light guides, which are needed in traditionally built $\mu$SRinstrument to deliver the scintillation light to photomultiplier tubes locatedoutside magnetic fields applied, allowed us to design a compact instrument witha detector set covering an increased solid angle compared to the old GPS.