Optical Characterization Measurements of Commercial Polyvinyltoluene Scintillators for Accurate Geant4 Detector Modeling
Year: 2026
Type: preprint
Abstract: Accurate Monte Carlo simulation of plastic scintillator detectors requires precise wavelength-dependent optical properties. We present measurements of wavelength-dependent refractive index $n(λ)$ and bulk absorption length $L_{\mathrm{abs}}(λ)$ for six commercial polyvinyltoluene (PVT)-based scintillators (Saint Gobain BC-400, BC-404, BC-408, BC-418, BC-422, and BC-430) at five wavelengths between 372 and 660 nm. Using a precision refraction apparatus and variable-thickness transmission measurements, we characterize material-specific dispersion that deviates substantially from both the manufacturer specification and literature values for pure PVT. Illustrative Geant4 simulations of a BC-422 detector demonstrate a 7.2% reduction in photocathode energy-deposition threshold events when using our measured $n(λ)$ compared to the constant manufacturer value, highlighting the practical importance of accurate optical property data for detector design and calibration. We successfully measure absorption lengths for BC-430 at four wavelengths between 372 and 505 nm (2.2-12.4 mm) and for all materials at 372 nm (2.2-38 mm), while establishing lower bounds exceeding 750 mm for weakly absorbing formulations at longer wavelengths.
Source: arXiv (Cornell University)
Language: English
Subfield: Radiation
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funder: U.S. Department of Energy
Awards: G14554683, G2145270357
OpenAlex ID: W7203615551