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

APS April meetingJacksonville, 2007

WIMP Search WithDEAP-1 @ SNOLAB

Chris JillingsSNOLAB Staff Scientist

For the DEAP-1 Collaboration


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.


-CDM with ~25% CDMequiv to 5 H atom per m3

Large-scale structure

Gravitational lensing

CMB

The Dark Matter Problem


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


DEAP-1Quartzwindow

7 kg LAr

5” PMTETL 9390Bin polypro

8” long acrylicLight guide

Reflectivecoating &TPB

TPB


The Detector


Backgrounds

• 39 Ar

• Other betas and gammas

• External neutrons

• (,n) in detector materials

• Surface contamination


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


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


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


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/

http://www.snolab.ca/


(,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.


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


Deep for DEAP

Mei and Hime: astro-ph/0512125

Flat-overburden sites


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.


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



Gas and Liquid Flow

Documents

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