Radiopurity measurement of acrylic for the DEAP-3600 dark matter experiment

The liquid argon target of the DEAP-3600 dark matter detector is contained by an extremely radiopure acrylic vessel. Alpha decays from the inner surface of the acrylic vessel are a source of background. If a fraction of the alpha energy is observed, or if the recoiling nucleus from the alpha decay is observed, the event will not be separated from a dark matter candidate event. In addition to the low level of inherent contamination from uranium and thorium, the Pb-210 from Rn-222 diffusion during manufacturing must be measured. The limit for the DEAP-3600 acrylic vessel is 1.1 × 10^−20 g/g Pb-210. By vaporizing a large quantity of acrylic and counting the concentrated residue with an ultralow background HPGe well detector and a low background alpha spectrometer, the bulk acrylic was found to have an upper limit of 10^−19 g/g Pb-210. The design, installation, commissioning, operation, and analysis for various aspects of the acrylic assay are described.

Department dc:contributor.department

Physics, Engineering Physics and Astronomy

Year dc:date.issued

2014

Author dc:creator

• Nantais, Corina

Advisor dc:contributor.supervisor

• Boulay, Mark Guy

• poly(methyl methacrylate)
• Pb-210

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1974/8554

OAI identifier oai:identifier

oai:queensu.scholaris.ca:1974/8554