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Carlos Vivo-Vilches (Carleton)

Event Details

McDonald Institute Seminar Series

Location: STI 501

Date: January 28, 2020

Time: 11:30am - 12:30pm

Accelerator mass spectrometry Survey of Trace Radionuclides for Experiments on Astroparticle physics (ASTREA)

Accelerator Mass Spectrometry (AMS) is a technique for the measurement of ultra-trace levels of long‑lived radionuclides. Since it was developed more than 40 years ago, AMS has been used to measure different cosmogenic and/or anthropogenic radionuclides, such as 10Be, 14C, 26Al, 36Cl, 41Ca, 129I and 236U; and for several different applications.
The joint project of the Astroparticle Physics group at Carleton University and the André E. Lalonde AMS Laboratory at the University of Ottawa, ASTREA, has a different approach: the AMS assay of primordial radionuclides, such as 238U, 232Th and 210Pb. The objective is the application of AMS to the radioassay of materials for experiments looking for rare event searches in Astroparticle Physics, like neutrinoless double‑beta decay or direct dark matter detection.
238U and 232Th AMS is a challenging one since contamination cannot be avoided in the chemical preparation of the sample, which raises concern about how high this contamination can be. When possible, the use of the original sample, untreated, as sputtering target is preferred.
The measurement of 210Pb concentrations is closer to other radionuclide AMS in terms of procedures. The main difference is that the relatively low half-life of 210Pb (22.2 years), which actually makes possible, in most of the cases, its measurement by γ-counting or by the measurement of its daughter  210Po by α-spectrometry. Nevertheless, in some cases, these techniques do not have the sensitivity required to assay some samples, especially when the sample mass available is low. This is typically the case of polymer samples. AMS allows the assay of 210Pb on ultra-thin polymers, like Kapton, with a LOD down to 5 mBq/m2.
In this talk, we will discuss the recent works done by the Carleton group, to provide a proper calibration to U and Th AMS; and the assay of 210Pb concentrations in polymers thanks to the sensitivity provided by the AMS technique. We will also discuss the future capabilities of the technique, including its potential in other experiments and the usefulness of the radioassay of typical AMS radionuclides.