Simulation study of the light collection efficiency and the dependency on position resolution in plastic scintillator-based muography detectors

Abstract

Cosmic-ray muon imaging (muography) has been applied in various fields in recent years, in which plastic scintillators are one of the frequently selected detectors internationally. Therefore, a triangular scintillator strip based muography detection system has been proposed in the development of the μ Scattering and Transmission imaging faCility (μSTC). Before the mass production of detector units, this work studied the impacts of multiple factors on the light collection efficiency (LCE) and the position resolution (σ) of plastic scintillators. These factors include configurations of wavelength shifting (WLS) fibers, fiber grooves on scintillators, coupling optical glues and silicon photomultiplier (SiPM) readout mode. According to the simulated results, an empirical formula was proposed to quantitatively describe the relation between the LCE and σ, which has seldom been studied before. In this formula, σ reduces as a power-law function of the LCE. The SiPM readout mode (single-end or double-end output) and fiber groove treatments show no significant influence on the σ-LCE relation. LCE variations due to different factors lead to a difference in σ of less than 0.2 mm in the whole range of LCE. Accordingly, these factors are nearly equivalent in the improvement of detector position resolution. In comparison, the muon hit position reconstruction method nearly halves the σ after using angular and gap corrections. Thus, a better reconstruction method shows greater importance than the efforts made to increase LCEs. The simulation study in this work will provide good references for the construction of plastic scintillators of the μSTC platform in the near future.