Performance of newly constructed plastic scintillator barrel in the WASA-FRS experiments and evaluation of radiation damage effects on multi-pixel photon counter

TL;DR

This paper reports on the development and testing of a plastic scintillator barrel with MPPC readout for particle detection in the WASA-FRS experiment, demonstrating high time resolution, stable high-rate performance, and radiation damage effects.

Contribution

It introduces a new plastic scintillator detector with MPPC readout optimized for high-rate particle detection and evaluates its performance and radiation damage effects in a nuclear physics experiment.

Findings

Achieved 45-75 ps time resolution depending on energy deposition.

Maintained stable performance at rates up to 1.35 MHz per counter.

Observed 35% signal amplitude reduction due to radiation damage at specified fluence.

Abstract

A barrel-shaped plastic scintillation counter with Multi-Pixel Photon Counter (MPPC) readout has been developed and operated in the first WASA-FRS experimental campaign at GSI. The detector was used to measure charged particles emitted from reactions induced by a 2.5 GeV proton beam incident on a carbon target, providing particle identification in combination with momentum reconstruction in a 1 T magnetic field. The performance of this detector, particularly its response to energy deposition and time resolution, was systematically investigated as a function of count rate and total number of irradiating protons. A time resolution of 45-75 ps ($\sigma$), depending on the energy deposition, was achieved. Stable performance was maintained under high-rate conditions up to 1.35 MHz per single counter, with no significant degradation in either signal amplitude or timing response. Radiation-induced damage to the MPPCs was observed primarily as a reduction in signal amplitude, with approximately $35\%$ decrease at an estimated 1 MeV neutron-equivalent fluence of $2.4 \times 10^{10}$ cm$^{-2}$.