Ultra-low measurements of 40K for SNO+ utilizing accelerator mass spectrometry – Proof of principle

To increase sensitivity, experiments studying rare processes such as neutrino and dark matter interactions are forced underground to achieve the ultra-low levels of radioactive background they require. In conjunction with this, Accelerator Mass Spectrometry (AMS) can be used to help select the ultra-high purity and low background required for detector materials. One project interested in such techniques is SNO+ (Sudbury Neutrino Observatory), which proposes modifying the existing SNO detector set-up to study low-energy solar neutrinos as well as other neutrino properties via double-beta decay using a liquid scintillator called linear alkylbenzene (LAB). Due to the lower energy threshold of the proposed set-up, the present materials need to be re-evaluated for 40K concentrations. Ultra-pure copper cathodes and sample materials to be used in the new detector system were prepared at Idaho State University and Idaho National Laboratory. These materials are being tested for levels of 40K at the Notre Dame AMS facility. Proof of principle and results from the first set of measurements are discussed in this paper.