Ultra-low background mass spectrometry for rare-event searches

Understand

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.