Performance of X-rays crystal detectors with SiPM array readout exposed to the RIKEN-RAL low energy muon beam

Scintillating crystals coupled to SiPM array readout have been proposed to realize compact X-rays detectors for the FAMU experiment, which aims to accurately measure the hyperfine splitting of the ground state of the muonic hydrogen atom. A measurement of the transfer rate of muons from hydrogen to heavier gases is necessary for this purpose. Since 2014, in a series of test runs, a pressurized gas-target was exposed to the pulsed low-energy muon beam at the RIKEN RAL muon facility (Rutherford Appleton Laboratory, U.K.). The main goal of these tests was the characterization of both the background induced by the pulsed beam and the X-ray detectors. Preliminary results are shown on the use of new Pr:LuAG and Ce:GAGG crystals, developed for PET scanners and of more conventional LaBr3:Ce crystals, with a SiPM array readout. Energy spectra of the X-rays produced after the de-excitation of muonic atoms formed from the interaction of the beam muons with the gas target in the FAMU apparatus are shown, demonstrating the suitability of these detectors for muonic X-rays spectroscopy.