Acrylic purification and coatings

TL;DR

This paper presents a novel acrylic coating method to reduce radon-induced backgrounds in WIMP detectors, involving purification and specialized surface coatings tested on prototype and full-scale detectors.

Contribution

It introduces a new acrylic purification process and two coating techniques—solvent-borne and solvent-less—for improved detector surface contamination control.

Findings

Successful application of acrylic coating on DEAP-1 prototype

Development of solvent-less coating for DEAP-3600

Reduction of alpha background in detector surfaces

Abstract

Radon (Rn) and its decay daughters are a well-known source of background in direct WIMP detection experiments, as either a Rn decay daughter or an alpha particle emitted from a thin inner surface layer of a detector could produce a WIMP-like signal. Different surface treatment and cleaning techniques have been employed in the past to remove this type of contamination. A new method of dealing with the problem has been proposed and used for a prototype acrylic DEAP-1 detector. Inner surfaces of the detector were coated with a layer of ultra pure acrylic, meant to shield the active volume from alphas and recoiling nuclei. An acrylic purification technique and two coating techniques are described: a solvent-borne (tested on DEAP-1) and solvent-less (being developed for the full scale DEAP-3600 detector).