Improving the resolution and light yield in CsI(Tl) scintillators

Abstract

In the search for Dark Matter, very low-energy sensitive detectors are needed that would be able to distinguish minute differences in closely residing energy peaks. To increase the ability of CsI(Tl) scintillator detectors to do so, a different wrapping material will be used on the innermost layer of the detector. This wrapping material is a 3MTM Enhanced Specular Reflector (ESR) material which is hypothesized to produce a higher light yield with better resolution than the PTFE wrapping of plumber’s tape due to its high reflectivity. Two different types of measurements were carried out to test this hypothesis. Each test was run on a different half of a CsI(Tl) rectangular crystal of volume 48 in3. First, a source of 60Co was used to test the difference between the wrappings. The test was run an hour for the PTFE and the ESR wrapping. We observe a 35% increase in the ADC count for each 60Co energy peak and 15% decrease in the value of the standard deviation around those peaks. Secondly, a source of 241Am was used to test the low-energy capabilities of the ESR material. Here also we see a significant increase in the ADC count for the two energy peaks of the 241Am source. Due to the high photon reflectivity capability of the ESR film, our detector is more capable of collecting photons created by low-energy interactions. As we know Dark Matter produces very low-energy recoils, while interacting with the detector target material, so the ability to contain a maximum number of photons within the detector volume will help us move one step closer to detecting the rare interaction. Because of this significant increase in light yield and general decrease in standard deviation, it is clear that the ESR material has a greater ability to gather higher resolution data than its predecessor. This could lead to a greater understanding of low-energy particles, which in turn could help us understand what Dark Matter really is.