Radon Reduced Air and SNOLAB Aksel Hallin Queen’s University August, 2006

Radon is a major issue for low background experiments SNO Acrylic vessel and NCD’s Kamland Scintillator Borexino purification system SNO Cover gas Majorana, DEAP internal parts Average air in Canada 20 Bq/m 3 ; u/g 130 Bq/m 3 More serious problem as detectors get bigger

There is a significant effort in the community (See LRT proceedings and theses)

Radon daughters are electrically charged,and drift in electrical fields. They plate out on various surfaces. Also have physical and chemical adsorbtion of radon and its daughters. (See Michael Leung’s thesis)

Four aspects of radon Monitoring Radon reduced environments Desorption of daughters into detector volumes Cleaning surfaces

Monitoring Techniques typically involve concentrating radon into an active volume cryogenically or using electrostatics to concentrate the daughters and then counting alphas. Technology is well developed

Radon reduced environments SNO covergas system SNO water system Highest purity, low flow Limited by radon ingress Excludes personnel

Andrea Pocar, PhD Thesis, Princeton, 2003

Radon Clean Laboratory Concept Radon scrubber HEPA Lab Equipment 20 Bq/m 3 9.4x Rn/m 3 30 m 3 /min (100 cfm) People/ processes.0002 Bq/m Rn/m Rn total Class 1000 Clean Room? Bq/m Rn/m 3.02 Bq/m 3 9, Rn/m 3 2 Bq/m 3 940, Rn/m 3 3m x 10m x 10m 90 m 3 room 140 m 2 area emanation 23 Rn/min If walls 10 Rn/m 2 hr Air Lock #1 Air Lock #2 3 m 3 /min 80 Rn/min 48 Rn/min Leaks/diffusion 23 Rn/min 28 Rn/min Tolerable Rn load = Rn scrubber flow rate times Acceptable Rn concentration = 3 m 3 /min x 94 Rn/m 3 = 282 Rn/min Electrostatic deposition plates Chemical Baths? Lights Cooler Radon scrubber (1 cfm) K. McFarlane May 16, 2006 Baffle 9, Rn in lungs 125, Rn dissolved o o Continuous radon monitoring

Cleaning contaminated acrylic Cleaning quartz and other materials discussed in Michael Leung’s thesis