DEAP Dark Matter Experiment with Argon PSD Mark

DEAP: Dark Matter Experiment with Argon PSD Mark Boulay Canada Research Chair in Particle Astrophysics Queen’s University arxiv. org: /astro-ph/0402007 Mark Boulay SNOLab Aug 16/05

Outline: • DEAP defined • Scintillation properties of LAr • Gamma vs recoil separation for LAr and other techniques • Some advantages of LAr • Design of and Results from DEAP-0: 1 kg LAr cryostat at LANL (preliminary results) • Plans for DEAP-1: 10 kg LAr cryostat at Queen’s (SNOLab early space) • Possible timeline to DEAP-3: 1000 kg LAr Mark Boulay SNOLab Aug 16/05

What is DEAP? • Direct dark matter particle search, single-event sensitive • Spin-independent WIMP-nucleon scattering on liquid 40 Ar • Spherical volume of LAr instrumented with PMTs to detect scintillation photons • Discrimination of g/b backgrounds (including 39 Ar) using only scintillation time information from PMTs • Generic spherical design scaleable to large target mass • Clean materials and UG deployment to mitigate neutron background DEAP-n: n = log 10(target mass [kg]) Mark Boulay SNOLab Aug 16/05

http: //arxiv. org/astro-ph/0411358 scintillation pulseshape analysis for discrimination of e- vs nuclear recoils -> no electron-drift DEAP : Dark-matter Experiment with Argon PSD Mark Boulay SNOLab Aug 16/05

g versus recoil separation in CDMS Collection of small detectors simultaneously measure deposited energy in charge and phonon channels ~1 kg / “tower” g rays Current best limit neutrons Images from CDMS ZIP detector 250 g Ge Image from cdms. berkeley. edu Mark Boulay SNOLab Aug 16/05

Idea is to use scintillation photons only for discrimination in DEAP… …allows for simple detector design and possibly a more easily realizeable large-scale experiment Mark Boulay SNOLab Aug 16/05

Some advantages of LAr • Inexpensive : 10 kg = 25$ or LAr • Good light yield, 40000 photons/Me. V • Used extensively, very large experiments underground • Easily accessible temperature (~85 K) • Same requirements as LN for cryogenic components • Good pulse shape discrimination->background rejection • Similar cross-section to Xe for SI interactions • Liquid experiment can be continuously or periodically purified (advantage over crystals) • Allows simple, inexpensive, scalable design • Could be complementary to heavier-mass target searches Mark Boulay SNOLab Aug 16/05

Simulation of PSD in argon • 6 pe/ke. V for 75% coverage, with • 1500 Hz PMT noise • Backgrounds from Ham. R 9288 (approx. 70 m. Bq/PMT) • 5 ns PMT resolution • 20% photon detection efficiency • 100 ns trigger window sets T 0 • Fprompt = Prompt hits(100 ns)/Total hits(15 us) • ~2 kg Ar with 10 ke. Vee threshold (60 pe) Dominant backgrounds assuming proper shielding, depth, and clean construction. Mark Boulay SNOLab Aug 16/05

Background rejection with LAr (simulation) 108 From simulation, rejection > 108 @ 10 ke. V (>>!) simulated e-’s 100 simulated WIMPs Mark Boulay (Goal for Super. CDMS is 108) SNOLab Aug 16/05

DM Sensitivity with LAr with 1 -year exposure LAr with 10 ke. V (electron) threshold Mark Boulay SNOLab Aug 16/05

DEAP-0 (1 kg) at LANL 40” • PMT in air outside of large vacuum chamber • ~1 kg LAr viewed by single 2” PMT • calibration with g’s, n’s (tagged 22 Na and Am. Be) • Demonstration of PSD • Test long term gain stability DEAP-0 Timeline: DEAP-0 Design: Jan 05 M. Boulay, A. Hime, L. Rodriguez (LANL) Order components: Feb 05 Supported by LANL LDRD, Rec’d all components: 05 with technical assistance. May and advice from: Assembly: June, Jul 05 Steve Lamoreaux, Dan Mc. Kinsey, Data run & analysis: Jul, Aug 05 James Nikkel, Seppo Pentilla, … (Analysis being completed) Mark Boulay SNOLab Aug 16/05

Gas Handling System for DEAP-0 SAES purifier, < 0. 1 ppb Mark Boulay SNOLab Aug 16/05

DEAP-0 construction at LANL • Conflat construction, Cu gaskets, “standard” components where possible to reduce cost • ~1 kg of liquid argon with 2” windows, viewed by 1 PMT in air Mark Boulay SNOLab Aug 16/05

DEAP-0 Construction at LANL Liquid nitrogen cooling, Ar gas in Cu coils Mark Boulay SNOLab Aug 16/05

DEAP-0 Mark Boulay SNOLab Aug 16/05

DEAP-0 in vacuum chamber Mark Boulay SNOLab Aug 16/05

DEAP-0 PMT setup at PMT coupled to LAr through chamber window Source with Cs. I/PMT for gamma tag Vacuum chamber windows Mark Boulay Cs. I tag LAr PMT source SNOLab Aug 16/05

DEAP-0 windows (post-warm-up) Window to argon chamber …room for improvement! Mark Boulay SNOLab Aug 16/05

PMT pulses from LAr, in coincidence with g in Cs. I g-like neutron-like Mark Boulay SNOLab Aug 16/05

Triplet lifetime check Mark Boulay SNOLab Aug 16/05

Discrimination in liquid argon Na-22 runs 4 x 106 tagged g’s Mark Boulay Am. Be runs <pe/ke. V> = 0. 1 SNOLab Aug 16/05

Discrimination in liquid argon from DEAP-0 <pe> = 60 preliminary O(1 in 105) consistent with random coincidence with room neutrons (preliminary) <pe> = 60 corresponds to 10 ke. V with 75% coverage • Final analysis and systematics evaluation being done Mark Boulay SNOLab Aug 16/05

DEAP-1 Queen’s University Mark Boulay, Mark Chen, Kevin Graham, Aksel Hallin, Jeff Lidgard, Reuble Matthew, Peter Skensved, +technical support Los Alamos National Laboratory Andrew Hime, Steve Lamoreaux, Dong-Ming Mei, Larry Rodriguez Opportunities for Post-docs and students Mark Boulay SNOLab Aug 16/05

DEAP-1 Timeline and SNOLab • Currently designing cryostat, selecting components NOTE: working out background budget, radiopurity requirements including (a, n), random coincidences, etc • Clean room being constructed at Queen’s • Plan is to construct and commission DEAP-1 at Queens O(6 months) • Calibration & verification of PSD above ground, spring/summer 2006 • Seek “early” SNOLab space September 2006 for UG running (1 -2 m experiment) • No unusual infrastructure requirements • 10 -44 cm 2 with one year livetime • Plan to submit LOI to SNOLab EAC Funding for DEAP-1 is in place with CFI/startup grant from Queen’s and LANL LDRD support O(750 K total) • Philosophy is to design DEAP-1 so that scaling to DEAP-3 is feasible, x 100 improvement in background required • DEAP-3 proposal 2007 -2008 ? DEAP-3 in 2009 -2010? • Will examine feasibility of active veto Mark Boulay SNOLab Aug 16/05

Neutron active veto (conceptual) Note: thermal neutron capture cross-section on Ar: 675 mbarn Active neutron veto LAr Vacuum region n • Active veto can mitigate internal and external low-energy (a, n) neutrons • Relaxes internal (a, n) requirements • Possible overlap with SNO+ for liquid scintillator active veto • Possible interest from other SNOLab experiments? • Ideally suited for coordination by SNOLab RS? Mark Boulay SNOLab Aug 16/05

Conclusions • DEAP-0 (1 kg) succesfully executed at LANL • Demonstrated discrimination using PSD only in LAr • Discrimination sufficient for 39 Ar suppression (preliminary result) • Currently designing DEAP-1 (10 kg) for construction at Queen’s • Possibly ready for deployment in early SNOLab space (Sept 2006) 10 -44 cm 2 sensitivity with 1 live-year, 10 ke. V threshold • Funding for DEAP-1 in place, CFI/startup + LANL LDRD • Scaling to DEAP-3 will be studied in parallel with design of DEAP-1, O($3 M) Mark Boulay SNOLab Aug 16/05