  Compact X-rays detectors made of 1/2" or 1" :LaBr3:Ce crystals of cubic shape
with SiPM array readout have been developed for the FAMU experiment at
RIKEN-RAL. The aim is a precise measurement of the proton Zemach radius with
incoming muons. Additional applications may be found in medical physics, such
as PET, homeland security and gamma-ray astronomy. Due to the high photon yield
of LaBr3:Ce it was possible to use a simple readout scheme based on CAEN V1730
digitizers. Detectors, using Hamamatsu S13361 or S14161 arrays, have good FWHM
energy resolutions up to 3 % (8 %) at the Cs137 Co57) peak, comparing well with
the best results obtained with a photomultiplier's readout. Detailed studies
were performed to correct online the drift with temperature of SiPM gain and to
reduce the risetime/falltime of detectors' signals, that increased going from
1/2" to 1" detectors, due to the larger capacity of the used SiPM arrays.
