Temperature dependence of alpha-induced scintillation in the 1,1,4,4-tetraphenyl-1,3-butadiene wavelength shifter

TL;DR

This study investigates how temperature affects alpha-induced scintillation in TPB, revealing temperature-dependent pulse shapes and light yields that could improve background discrimination in dark matter detectors.

Contribution

It provides the first detailed characterization of temperature-dependent pulse shapes and light yields of alpha-induced TPB scintillation, aiding background mitigation strategies.

Findings

Pulse shape varies significantly with temperature.

Long time constants enable alpha and nuclear recoil discrimination.

Light yield decreases at lower temperatures.

Abstract

Liquid noble based particle detectors often use the organic wavelength shifter 1,1,4,4- tetraphenyl-1,3-butadiene (TPB) which shifts UV scintillation light to the visible regime, facilitating its detection, but which also can scintillate on its own. Dark matter searches based on this type of detector commonly rely on pulse-shape discrimination (PSD) for background mitigation. Alpha-induced scintillation therefore represents a possible background source in dark matter searches. The timing characteristics of this scintillation determine whether this background can be mitigated through PSD. We have therefore characterized the pulse shape and light yield of alpha induced TPB scintillation at temperatures ranging from 300 K down to 4 K, with special attention given to liquid noble gas temperatures. We find that the pulse shapes and light yield depend strongly on temperature. In addition, the significant contribution of long time constants above ~50 K provides an avenue for discrimination between alpha decay events in TPB and nuclear-recoil events in noble liquid detectors.