APS April meeting Jacksonville, 2007 WIMP Search With DEAP-1 @ SNOLAB Chris Jillings SNOLAB Staff Scientist For the DEAP-1 Collaboration
Jan 03, 2016
APS April meetingJacksonville, 2007
WIMP Search WithDEAP-1 @ SNOLAB
Chris JillingsSNOLAB Staff Scientist
For the DEAP-1 Collaboration
APS April meetingJacksonville, 2007
Dark matter Experimentwith Argon and
Pulse-shape discrimination
1. Direct WIMP dark-matter detection2. The detector3. 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 10-44 cm2.
It will demonstrate pulse-shape discriminationbetween electromagnetic events and nuclear recoils
at the level of 1 event in 108.
APS April meetingJacksonville, 2007
-CDM with ~25% CDMequiv to 5 H atom per m3
Large-scale structure
Gravitational lensing
CMB
The Dark Matter Problem
APS April meetingJacksonville, 2007
Direct Detection
40Ar
40Ar
Use WIMP-nuclear elastic scattering:
Liquid argon scintillates in the far UV. Use wavelengthshifter (TPB) to convert to blue light.
LAr light yield ~ 40 photons/keV electron energy
Boulay and Himehttp://arxiv.org/astro-ph/0411358
APS April meetingJacksonville, 2007
DEAP-1Quartzwindow
7 kg LAr
5” PMTETL 9390Bin polypro
8” long acrylicLight guide
Reflectivecoating &TPB
TPB
APS April meetingJacksonville, 2007
Backgrounds
• 39 Ar
• Other betas and gammas
• External neutrons
• (,n) in detector materials
• Surface contamination
APS April meetingJacksonville, 2007
39Ar• 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
Advertisements: DEAP-1: Bei Cai E14-00007 CLEAN: Hugh Lippincott E14-00009
0 keV 600 keV
0 60 keV20
Xe
Ar
APS April meetingJacksonville, 2007
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
Acrylic222Rn
218Po
218Po
210Po
206Pb
APS April meetingJacksonville, 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 meetingJacksonville, 2007
Gamma and Neutron Flux
FluxMuonsNeutrons (Thermal)Neutrons (Fast) Radon (Surface)Radon (UGLab) 3.3± 0.4 pCi/L
NoriteK 1.20%238U 1.2 ppm232Th 3.2ppm
<0.27/m_/day4144.9±49.8±105.3 n/m_/day~4000 n/m_/day0.15± 0.12 pCi/L
Data from SNOLAB Users Handbookhttp://www.snolab.ca/
APS April meetingJacksonville, 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 meetingJacksonville, 2007
SNOLAB
Located at CVRD INCO’s nickel mine near Sudbury, Ontario
Shower,Lunch roomOffices,Meeting roomSNO
cavity
Waterplant
Car wash
Cube Hall
Cryopit
Ladder labs
APS April meetingJacksonville, 2007
Deep for DEAP
Mei and Hime: astro-ph/0512125
Flat-overburden sites
APS April meetingJacksonville, 2007
Lab SpaceExcavation Clean Rm Laboratory
Area Volume Area Volume Area Volume
Existing
Existing+ Phase I
Existing
+ Phase I &I I
20,049 f t 2 582,993 f t 3 12,196 f t 2 470,360 f t 3 8,095 f t 2 412,390 f t 3
1,863 m2 16,511 m3 1,133 m2 13,321 m3 752 m2 11,679 m3
65,340 f t 2 1,367,488 f t 3 41,955 f t 2 1,049,393 f t 3 26,117 f t 2 837,604 f t 3
6,072 m2 38,728 m3 3,899 m2 29,719 m3 2,427 m2 23,721 m3
77,636 f t 2 1,647,134 f t 3 53,180 f t 2 1,314,973 f t 3 32,877 f t 2 1,043,579 f t 3
7,215 m2 46,648 m 3 4,942 m2 37,241 m3 3,055 m2 29,555 m3
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 meetingJacksonville, 2007
Installation at SNOLABSNOLAB approved siting DEAP-1 in SNO control room.
CurrentSurface Data at Queen’s
Summer 2007Install at site
Run Plan18 months physics data+ calibrations+ background runs