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DEAP-1 Dark Matter Experiment: WIMP Detection with Argon

Explore the DEAP-1 liquid-argon detector and its pulse-shape discrimination capabilities for WIMP dark matter detection. Learn about its run plan, background reductions, and detection methods in this informative presentation from the APS April meeting in Jacksonville, 2007.

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DEAP-1 Dark Matter Experiment: WIMP Detection with Argon

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  1. WIMP Search WithDEAP-1 @ SNOLAB Chris Jillings SNOLAB Staff Scientist For the DEAP-1 Collaboration APS April meeting Jacksonville, 2007

  2. Dark matter Experimentwith Argon andPulse-shape discrimination • Direct WIMP dark-matter detection • The detector • Backgrounds and pulse-shape discrimination (PSD) • Run plan for SNOLAB DEAP-1 is a 7 kg liquid-argon detector with sensitivity to WIMP dark matter of 10-44 cm2. It will demonstrate pulse-shape discrimination between electromagnetic events and nuclear recoils at the level of 1 event in 108. APS April meeting Jacksonville, 2007

  3. The Dark Matter Problem CMB Large-scale structure Gravitational lensing L-CDM with ~25% CDM equiv to 5 H atom per m3 APS April meeting Jacksonville, 2007

  4. Direct Detection 40Ar  40Ar  Use WIMP-nuclear elastic scattering: Boulay and Hime http://arxiv.org/astro-ph/0411358 Liquid argon scintillates in the far UV. Use wavelength shifter (TPB) to convert to blue light. LAr light yield ~ 40 photons/keV electron energy APS April meeting Jacksonville, 2007

  5. DEAP-1 Quartz window 8” long acrylic Light guide 7 kg LAr 5” PMT ETL 9390B in polypro Reflective coating & TPB TPB APS April meeting Jacksonville, 2007

  6. The Detector APS April meeting Jacksonville, 2007

  7. Backgrounds • 39 Ar • Other betas and gammas • External neutrons • (,n) in detector materials • Surface contamination APS April meeting Jacksonville, 2007

  8. 39Ar 0 keV 600 keV • Advertisements: • DEAP-1: Bei Cai E14-00007 • CLEAN: Hugh Lippincott E14-00009 • N 39Ar = Activity x (Area ROI) x (1 year) x (7kg) • Activity (WARP astro-ph/0603131) = 0.87  0.02  0.08Bq/kg • ROI (10 to 50 keV) ~ 0.2 • ~ 3 x 107 events • Goal = 0.2 events background • Requires leakage of electrons to <10-8 PSD Xe Ar 0 20 60 keV APS April meeting Jacksonville, 2007

  9. Surface Backgrounds  • Radon in air during handling • Daughter 218Po plates • Subsequent  decays embed nucleus in surface • Pass through 210Pb (22 year half life) • 210Po alpha decays • Recoil nucleus enters LAr Acrylic 222Rn 218Po 218Po 210Po 206Pb  APS April meeting Jacksonville, 2007

  10. Surface Backgrounds • Remove surface of all acrylic parts. • Coat surfaces. • Store in sealed (and purged) container. • Build detector with minimum exposure to air. • Using gaseous-argon test cell • Expose acrylic to elevated Radon levels (spike) • Verify previous measurements APS April meeting Jacksonville, 2007

  11. Gamma and Neutron Flux Data from SNOLAB Users Handbook http://www.snolab.ca/ APS April meeting Jacksonville, 2007

  12. (,n) and External Neutrons • Monte-Carlo Studies: • Use measured SNOLAB neutron rates • Use (,n) from material assays • Target  1 neutron per year • Replace Al dark box with SS • Fill dark box with polypropylene • Monte Carlo results indicate target will be met. APS April meeting Jacksonville, 2007

  13. SNOLAB Located at CVRD INCO’s nickel mine near Sudbury, Ontario Cryopit Cube Hall Ladder labs Car wash Water plant Shower, Lunch room Offices, Meeting room SNO cavity APS April meeting Jacksonville, 2007

  14. Deep for DEAP Flat-overburden sites Mei and Hime: astro-ph/0512125 APS April meeting Jacksonville, 2007

  15. Lab Space • Laboratory and support spaces will be operated as Class 2000 clean rooms. 10 HEPA filtered air changes per hour. • Infrastructure includes: 2MW electrical service, 1 MW chiller capacity, emergency generator, Ultra Pure Water facility, Low background counting facility, high bandwidth network access, chemistry facilities, underground machine shop, light gauge rail line for material transport. APS April meeting Jacksonville, 2007

  16. Installation at SNOLAB SNOLAB approved siting DEAP-1 in SNO control room. Current Surface Data at Queen’s Summer 2007 Install at site Run Plan 18 months physics data + calibrations + background runs APS April meeting Jacksonville, 2007

  17. APS April meeting Jacksonville, 2007

  18. Gas and Liquid Flow APS April meeting Jacksonville, 2007

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