First tests in the application of silicon photomultiplier arrays to dose monitoring in hadron therapy

A detector head composed of a continuous LaBr₃ crystal coupled to a silicon photomultiplier array has been mounted and tested, for its use in a Compton telescope for dose monitoring in hadron therapy. The LaBr₃ crystal has 16 mm×18 mm×5 mm size, and it is surrounded with reflecting material in five faces. The SiPM array has 16 (4 ×4) elements of 3 mm×3 mm size. The SPIROC1 ASIC has been employed as readout electronics. The detector shows a linear behavior up to 1275 keV. The energy resolution obtained at 511 keV is 7% FWHM, and it varies as one over the square root of the energy up to the energies tested. The variations among the detector channels are within 12%. A preliminary measurement of the timing resolution gives 7 ns FWHM. The spatial resolution obtained with the center of gravity method is 1.2 mm FWHM. The tests performed confirm the correct functioning of the detector.