Characterization of the scintillation anisotropy in crystalline stilbene scintillator detectors

TL;DR

This study characterizes the directional dependence of scintillation response in crystalline stilbene detectors, confirming anisotropy effects and extending previous findings to solution-grown stilbene, with implications for neutron detection accuracy.

Contribution

First measurements of scintillation anisotropy in solution-grown stilbene, confirming internal structural effects as the cause of directional dependence.

Findings

Crystalline stilbene exhibits directional scintillation anisotropy.

Solution-grown stilbene shows similar anisotropic behavior.

Liquid and plastic detectors do not show directional dependence.

Abstract

This paper reports a series of measurements that characterize the directional dependence of the scintillation response of crystalline melt-grown and solution-grown stilbene to incident DT and DD neutrons. These measurements give the amplitude and pulse shape dependence on the proton recoil direction over one hemisphere of the crystal, confirming and extending previous results in the literature for melt-grown stilbene and providing the first measurements for solution-grown stilbene. In similar measurements of liquid and plastic detectors, no directional dependence was observed, confirming the hypothesis that the anisotropy in stilbene and other organic crystal scintillators is a result of internal effects due to the molecular or crystal structure and not an external effect on the measurement system.