A new detector system for the ALC spectrometer—First experience with G-APDs in μSR instrumentation

Abstract The development of a new detector system for the avoided level crossing (ALC) μ SR -spectrometer, located at the Swiss Muon Source of the Paul Scherrer Institut, is presented. The distinctive feature of the new ALC-detector is the absence of the traditionally used components photomultiplier tubes and light guides. Their functionality is taken over by Geiger-mode avalanche photodiodes (G-APDs) and wavelength-shifting fibers. This approach allows us to build a compact, magnetic field insensitive detector, requiring low operation voltage.