Control of contamination of radon-daughters in the DEAP-3600 acrylic vessel
Aug 12, 20134 pages
Part of Proceedings, 4th Topical Workshop on Low Radioactivity Techniques (LRT 2013) : L'Aquila, Italy, April 10-12, 2013, 86-89
Published in:
- AIP Conf.Proc. 1549 (2013) 1, 86-89
Contribution to:
- , 86-89
- LRT 2013
- Published: Aug 12, 2013
DOI:
Experiments:
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Abstract: (AIP)
DEAP-3600 is a 3600kg single-phase liquid-argon dark matter detector under construction at SNOLAB with a sensitivity of 10−46cm2 for a 100 GeV WIMP. The argon is held an an acrylic vessel coated with wavelength-shifting 1,1,4,4-tetraphenyl-1,3-butadiene (TPB). Acrylic was chosen because it is optically transparent at the shifted wavelength of 420 nm; an effective neutron shield; and physically strong.With perfect cleaning of the acrylic surface before data taking the irreducible background is that from bulk 210Pbactivity that is near the surface. To achieve a background rate of 0.01 events in the 1000-kg fiducial volume per year of exposure, the allowed limit of Pb-210 in the bulk acrylic is 31 mBq/tonne (= 1.2 × 10−20g/g). We discuss how pure acrylic was procured and manufactured into a complete vessel paying particular attention to exposure to radon during all processes. In particular field work at the acrylic panel manufacturer, RPT Asia, and acrylic monomer supplier, Thai MMA Co. Ltd, in Thailand is described. The increased diffusion of radon during annealing the acrylic at 90C as well as techniques to mitigate against this are described.- Surface cleaning
- Annealing
- Asia
- Dark matter
- Diffusion
- radon: diffusion
- surface
- background: radioactivity
- DEAP-3600
- plastics
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