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Radon Reduced Air and SNOLAB

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

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Radon Reduced Air and SNOLAB

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

  2. 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/m3; u/g 130 Bq/m3 • More serious problem as detectors get bigger

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

  4. 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)

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

  6. 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

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

  8. Andrea Pocar, PhD Thesis, Princeton, 2003

  9. Tolerable Rn load = Rn scrubber flow rate times Acceptable Rn concentration = 3 m3/min x 94 Rn/m3 = 282 Rn/min .00002 Bq/m3 9.4 222Rn/m3 3m x 10m x 10m 90 m3 room 140 m2 area Radon Clean Laboratory Concept 28 Rn/min 3 m3/min Radon scrubber (1 cfm) Radon scrubber (100 cfm) Lights emanation 23 Rn/min If walls 10 Rn/m2hr Electrostatic deposition plates HEPA 20 Bq/m3 9.4x106222Rn/m3 Leaks/diffusion 23 Rn/min Cooler Continuous radon monitoring Baffle 30 m3/min Chemical Baths? 2 Bq/m3 940,000 222Rn/m3 Lab Equipment People/ processes Air Lock #2 Air Lock #1 9,400 222Rn in lungs 125,000 222Rn dissolved o o .02 Bq/m3 9,400 222Rn/m3 .0002 Bq/m3 94 222Rn/m3 8460 222Rn total Class 1000 Clean Room? 80 Rn/min 48 Rn/min 80 Rn/min K. McFarlane May 16, 2006

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

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