Search

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.

In prospect of its application in cryogenic rare-event searches, we have investigated the low-temperature scintillation properties of CaWO4 crystals down to 3.4 K under {\alpha} and {\gamma} excitation. Concerning the scintillation decay times, we observe a long component in the ms range which significantly contributes to the light yield below 40K. For the first time we have measured the temperature dependence of the {\alpha}/{\gamma}- ratio of the light yield. This parameter which can be used to discriminate {\alpha} and {\gamma} events in scintillating bolometers is found to be about 8-15% smaller at low temperatures compared to room temperature., Comment: The following article has been accepted by Journal of Applied Physics. After it is published, it will be found at http://scitation.aip.org/content/aip/journal/jap