Development of proton detectors using CsI(Tl) scintillator and SiPM

Experimental information on unstable nuclei, which is crucial to improve nuclear theory, can be investigated using radioactive isotope (RI) beams. We are developing recoil proton detectors useful for proton resonant scattering experiment with RI beams. Typically, a recoil detector needs to cover energies up to 20 MeV. A ΔE-E silicon detector with a total thickness of 2.5 mm meets this requirement. However, such a detector is expensive and CsI(Tl) scintillators are often used as cheaper alternatives to thick silicon detectors.

We developed prototype detectors combining a CsI(TI) crystal of 5.5 × 5.5 × 5.5 mm³ and SiPM (Silicon Photomultipliers) which became available in recent years. We fabricated three detectors with different SiPM with pixel pitches of 25, 50, and 75 μm, respectively, in order to study energy nonlinearity due to dead-time effect in photon counting of SiPM.

Energy resolution, energy linearity, and particle identification resolution were evaluated using proton and deuteron beams from the tandem accelerator at Kyushu University. We will report the results of the detector test and show plans of testing detectors in some reaction measurement and developing detectors with larger crystal sizes.