Ultra-low background mass spectrometry for rare-event searches

Abstract

Inductively Coupled Plasma Mass Spectrometry (ICP-MS) allows for rapid, high-sensitivity determination of trace impurities, notably the primordial radioisotopes ${}^{238}$U and ${}^{232}$Th, in candidate materials for low-background rare-event search experiments. We describe the setup and characterisation of a dedicated low-background screening facility at University College London where we operate an Agilent 7900 ICP-MS. The impact of reagent and carrier gas purity is evaluated and we show that twice-distilled ROMIL-SpA-grade nitric acid and zero-grade Ar gas delivers similar sensitivity to ROMIL-UpA-grade acid and research grade gas. A straightforward procedure for sample digestion and analysis of materials with U/Th concentrations down to 10 ppt g/g is presented. This includes the use of ${}^{233}$U and ${}^{230}$Th spikes to correct for signal loss from a range of sources and verification of ${}^{238}$U and ${}^{232}$Th recovery through digestion and analysis of a certified reference material with a complex sample matrix. Finally, we demonstrate assays and present results from two sample preparation and assay methods: a high-sensitivity measurement of ultra-pure Ti using open digestion techniques, and a closed vessel microwave digestion of a nickel-chromium-alloy using a multi-acid mixture.

8 pages; v2

References in corpus (3)

• Low Background Gamma Spectroscopy at the Boulby Underground Laboratory
• Identification of Radiopure Titanium for the LZ Dark Matter Experiment and Future Rare Event Searches
• A convenient approach to $10^{-12}g/g$ ICP-MS limits for Th and U in Aurubis electrolytic NA-ESN brand copper

Cited by in corpus (7)

• The LUX-ZEPLIN (LZ) Experiment
• The LUX-ZEPLIN (LZ) radioactivity and cleanliness control programs
• Low Background Gamma Spectroscopy at the Boulby Underground Laboratory
• The XLZD Design Book: Towards the Next-Generation Liquid Xenon Observatory for Dark Matter and Neutrino Physics
• Ultra-Low Background Germanium Assay at the Boulby Underground Laboratory
• Mass spectrometric analyses of high performance polymers to assess radiopurity as ultra low background materials for rare event physics detectors
• A new hybrid gadolinium nanoparticles-loaded polymeric material for neutron detection in rare event searches