Development of a method to measure trace level of uranium and thorium in scintillation films

TL;DR

This paper presents a sensitive method combining dry ashing and ICP-MS to measure trace levels of uranium and thorium in scintillation films, useful for low-background experiments.

Contribution

The authors developed a novel, highly efficient technique for detecting picogram-per-gram levels of uranium and thorium in scintillation materials, enhancing low-background measurement capabilities.

Findings

Achieved detection limits in the pg g$^{-1}$ range.

Demonstrated high collection efficiency (~100%) for trace isotopes.

Validated method on polyethylene naphthalate film.

Abstract

We have established a method to measure picograms-per-gram (pg g$^{-1}$) levels of $^{238}$U and $^{232}$Th in scintillation films by combining the dry ashing method and inductively coupled plasma mass spectrometry. Trace amounts of $^{238}$U and $^{232}$Th were measured in up to 2~g of the scintillation film with almost 100% collection efficiency. This paper details the experimental procedure, including the pretreatment of the samples and labware, detection limit of the method, collection efficiencies of $^{238}$U and $^{232}$Th, and measurement of $^{238}$U and $^{232}$Th in a polyethylene naphthalate film. This method is also applicable to $^{238}$U and $^{232}$Th measurements in other low-background organic materials for rare event search experiments.