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

APS April meeting Jacksonville, 2007 Dark matter Experiment with Argon and Pulse-shape discrimination 1.Direct WIMP dark-matter detection 2.The detector 3.Backgrounds and pulse-shape discrimination (PSD) 4.Run plan for SNOLAB DEAP-1 is a 7 kg liquid-argon detector with sensitivity to WIMP dark matter of cm 2. It will demonstrate pulse-shape discrimination between electromagnetic events and nuclear recoils at the level of 1 event in 10 8.

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

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

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

APS April meeting Jacksonville, 2007 The Detector

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

APS April meeting Jacksonville, Ar N 39 Ar = Activity x (Area ROI) x (1 year) x (7kg) Activity (WARP astro-ph/ ) = 0.87  0.02  0.08Bq/kg ROI (10 to 50 keV) ~ 0.2 ~ 3 x 10 7 events Goal = 0.2 events background Requires leakage of electrons to <10 -8 PSD Advertisements: DEAP-1: Bei Cai E  CLEAN: Hugh Lippincott E keV600 keV 0 60 keV 20 Xe Ar

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

APS April meeting Jacksonville, 2007 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 Gamma and Neutron Flux Data from SNOLAB Users Handbook

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

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

APS April meeting Jacksonville, 2007 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 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

APS April meeting Jacksonville, 2007 Gas and Liquid Flow