Background sources in low-background experiments

Abstract

Due to the elusive nature of neutrinos and dark matter, studies involving these rare phenomena require low-background experiments. These experiments are often situated underground or within mountains in deep underground laboratories because the rock serves as a barrier for cosmic muons. Muons, however, are not the only source of background. In this thesis, I study the main sources of background in low-background experiments: muons, neutrinos, neutrons, and radioactive impurities.

After a brief recap on the history of deep underground laboratories, I will present a review of where these backgrounds come from, what are their characteristics, and their most common interactions. I have included commonly used options for reducing these backgrounds or mitigating their effects. To date, there are tens of deep underground laboratories of varying depths. One of these is Callio Lab in the Pyhäsalmi Mine in Finland, where thorough natural background characterization has been done in preparation for possible low-background experiments. I will use Callio Lab as an example of how knowledge of background sources can be implemented for real-life usage.