A scintillator veto detector prototype for low energy charged beam particles

A detector prototype developed as a fast veto system for low-energy charged particles, designed to operate in a gaseous active target environment (Time Projection chamber, TPC) is presented. The detector employs a fast plastic scintillator optically coupled to a silicon photomultiplier (SiPM) through a light guide, enabling the relocation of the SiPM outside the active volume of the TPC. To enhance sensitivity to low-energy particles while minimizing energy losses, which is a general issue in the use of scintillators for charged particle detection, a thin platinum layer was deposited via a sputtering technique on the scintillator front surface. This layer acts, at the same time, as a light-tight window and as a reflective surface for the scintillation light produced within the active volume. This study, in particular, focuses on the use of NE-102A plastic scintillators (20 × 20 mm2, 3.2 mm thick) with a deposited platinum coatings ranging from 34 nm to 68 nm for the detection of low-energy light charged particles. Preliminary tests by using 3 × 3 mm2 SiPMs show a linear light response and an energy resolution comparable to those obtained by using standard aluminized Mylar windows. Further developments include coupling the scintillators with larger-area SiPMs (6 × 6 mm2) to further increase light collection efficiency, lower the energy threshold and improve energy resolution. The results of the prototype's characterization and functional testing are presented, along with an outlook on future improvements and applications.