A fast plastic scintillator for low intensity proton beam monitoring

TL;DR

This paper presents a fast organic scintillator-based detector with SiPM readout, achieving sub-235 ps time resolution and millimeter spatial accuracy for proton beam monitoring in particle therapy.

Contribution

Development and characterization of a novel fast scintillator detector with SiPMs for precise proton beam monitoring in vivo.

Findings

Time resolution of 120 ps FWHM at 63 MeV protons

Spatial resolution of approximately 2 mm rms

Proton energy measurement with 0.3% accuracy

Abstract

In the context of particle therapy monitoring, we are developing a gamma-ray detector to determine the ion range in vivo from the measurement of particle time-of-flight. For this application, a beam monitor capable to tag in time the incident ion with a time resolution below 235 ps FWHM (100 ps rms) is required to provide a start signal for the acquisition. We have therefore developed a dedicated detector based on a fast organic scintillator (EJ-204) of 25x25x1 mm3 coupled to four SiPM strips that allow measuring the particle incident position by scintillation light sharing. The prototype was characterised with single protons of energies between 63 and 225 MeV at the MEDICYC and ProteusONE facilities of the Antoine Lacassagne proton therapy centre in Nice. We obtained a time resolution of 120 ps FWHM at 63 MeV, and a spatial resolution of ~2 mm rms for single particles. Two identical detectors also allowed to measure the MEDICYC proton energy with 0.3% accuracy.