Designing a Lens-Coupled Plastic Scintillator as a Pulsed Beam Diagnostic

This work presents the design and characterization of a novel detector consisting of a plastic scintillator tile that uses a biconvex lens to couple to an optical fiber. The detector is intended for use as a beam diagnostic for pulsed power sources, specifically Los Alamos National Laboratory’s (LANL) Dual-Axis Radiographic Hydrodynamic Test Facility (DARHT). A series of these detectors is intended to be placed directly in the accelerator’s X-ray beam such that the neutron background may be deconvolved through time of flight calculations. This work outlines the use of the Geant4 Monte Carlo simulation toolkit to model the detector’s response including its light transport to the photomultiplier tube (PMT). These simulations were validated with benchtop calibration experiments. Additionally, scoring optical photons incident on the PMT’s photocathode by wavelength and time in simulation allows the detector to be used for absolute magnitude and timing measurements.