DEAP-3600

M. Kuzniak (on behalf of Mark Boulay)Queen’s University, Kingston

SNOLAB Opening Workshop May 14, 2012

@

DEAP CollaborationUniversity of Alberta

D. Grant, P. Gorel, A. Hallin, J. Soukup, C. Ng, B.Beltran, K. Olsen, R. Chouinard, T. McElroy, S. Crothers, S. Liu, P. Davis, and A. ViangreiroCarleton University

K. Graham, C. Ouellet, Carl BrownQueen's UniversityM. Boulay, B. Cai, D. Bearse, K. Dering, M. Chen, S. Florian, R. Gagnon, V.V. Golovko, P. Harvey, M. Kuzniak, J.J. Lidgard, A. McDonald, C. Nantais, A.J. Noble, E. O’Dwyer, P. Pasuthip, T. Pollman, W. Rau, T. Sonley, P. Skensved, L. Veloce, M. WardSNOLAB/Laurentian

B. Cleveland, F. Duncan, R. Ford, C.J. Jillings, M. BatygovSNOLAB

I. Lawson, K. McFarlane, P. Liimatainen, O. Li, E. Vazquez JaureguiTRIUMF

F. Retiere, Alex Muir, P-A. Amaudruz, D. Bishop, S. Chan, C. Lim, C. Ohlmann, K. Olchanski , V. Strickland

Rutherford Appleton Laboratory P. MajewskiRoyal Holloway University of London J. Monroe, J. Walding, A. ButcherUniversity of Sussex Simon Peeters

New UK collaborators

Outline

● Motivation

● Backgrounds

(and lessons learned from DEAP-1)

● Status and recent highlights

● Summary

Spin-independent Sensitivity (per nucleon) [x10-44 cm2]

Current Results

Under Construction or Operating

Proposed/ Future DevelopmentBeing Designed

High-Sensitivity Direct Dark Matter Searches

DEAP-3600 is well-positioned for leading sensitivity, v. good discovery potential (Note that for background-free exposure, sensitivity scales linearly with time, DEAP-3600 reaches XENON-100 sensitivity in < 1 month running)

Backgrounds in liquid argon (DM) detector

o b/g events: dominated by 39Ar rate, 1 Bq/kgPSD is very powerful in liquid argon, distinguish from recoils

o neutron recoils: (α,n)+fission, µ-inducedNO neutrons! (SNOLAB depth, clean detector materials, shielding)

o surface events: Rn daughters and other surface impuritiesclean surfaces in-situ, position reconstruction, limit radon

Mark Boulay, Queen’sMark Boulay

Yellow: Prompt light regionBlue: Late light region

Backgrounds (γ’s)

Nuclear Recoil

γ suppression better than 3x10-8 (45-89 keVee,

120-240 pe) using tagged g source

studies ongoing with higher light yield

PM

T p

ulse

hei

ght (

mV

)

AmBe neutron source

Background suppression with PSD in DEAP-1

Fpr

ompt

)s9(TotalPE

)ns150(omptPEPrFprompt µ

=

Mark Boulay, Queen’s

Pulse-shape discrimination in liquid argon

Want to maximize light yield! (high PMT coverage in DEAP-3600, drives decision for single-phase)

5x104

DEAP-3600 Detector3600 kg argon target (1000 kg fiducial)in sealed ultracleanAcrylic Vessel

Vessel is “resurfaced”in-situ to remove deposited Rn daughtersafter construction

255 Hamamatsu R5912 HQE PMTs 8-inch (32% QE, 75% coverage)

50 cm light guides + PE shielding provide neutron moderation

Detector in 8 m watershield at SNOLAB

8 July 2010 Fraser Duncan, MiniCLEAN Review

DEAP-1 (7kg LAr detector at SNOLAB)

12-05-14 M. Kuźniak 14

DEAP-1 and position sensitivity

Calibrated with a tagged Na22 source moved along the detector axis.

Size of the source C. Stanford (SNOLAB)

12-05-14 M. Kuźniak 15

Date Background Rate (in WIMP ROI)

Configuration Improvements forthis rate

April 2006 20 mBq First run (Queen’s) Careful design with input from materials assays (Ge γ couting)

August 2007 7 mBq Water shield (Queen’s)

Water shielding, some care in surface exposure (< a few days in lab air)

January 2008

2 mBq Moved to SNOLAB 6000 m.w.e. shielding

August 2008 400 µBq Clean v1 chamber at SNOLAB

Glove box preparation of inner chamber (reduce Rn adsorption/implantation on surfaces)

March 2009 150 µBq Clean v2 chamber at SNOLAB

Sandpaper assay/selection, PTFE instead of BC-620 reflector ,Rn diffusion mitigation, UP water in glove box, documented procedures; Rn Trap.

March 2010 130 µBq Clean v3 chamber at SNOLAB

Acrylic monomer purification for coating chamber. TPB purification.

Feb 2011 ~10 µBq Clean v4/v5 chamber at SNOLAB

Inner chamber redesign to remove “Neck Light” events

Surface background reduction in DEAP-1

12-05-14 M. Kuźniak 16

Backgrounds DEAP-1 v5

Low-energy backgrounds in DEAP-1 with and without PSD (3.8 pe/keVee)

5.2 ± 1.2 µBq/kg 25-40 keVee

=> Tina Pollman's thesis work, see the poster upstairsPaper in preparation

Preliminary

Energy [MeVr]

By-product: “Surface roughness interpretation of CRESST-II result”:arXiv:1203.1576Accepted for publication in Astropart. Phys.

Some recent updates:

Resurfacer: Assembled and started commissioning/testing at Queen’s

Filler Blocks: In production

Acrylic Vessel: Bonded, on the way to UofA

Light Guides: Started machining “production” light guides at TRIUMF

TPB deposition source: First successful operation of large-scale TPB vacuum deposition source at Queen’s (demonstrated required uniformity has been achieved)

Cryocooler and LN2 dewar system: acceptance tested at Stirling Cryogenics, installed u/g at SNOLAB

2800L liquid argon dewar: Finalized specification and received quote - all large cryogenic/purification system components now finalized

Steel Shell: In production

Purification system: Demonstration of radon emanation targets for argon purification system lines with citric acid passivation

20” test vessel: Started cooldown testing

Acrylic Vessel Resurfacer Now assembled at Queen’s

Will begin commissioning/ sanding tests on test blocks

Resurfacer will be emanated to demonstrate radon load(individual components have been emanated) before shipping to SNOLAB.

Filler block and LG design and prototyping complete

DEAP-3600 Acrylic Vessel Construction

Thermoform 4”-thick panels cast from pure MMA monomer(too much Rn in polymer beads)

Bond into sphere (Reynolds Polymer Tech.)

Machine with light guide ‘stubs’

Bond light guides UG at SNOLAB

DEAP-3600 Acrylic Vessel in Grand Junction, Colorado

Radiopure acrylic (Spartech) bonded into 8” blocks at Reynolds Colorado

Shipped to TRIUMF Jan 2012

Machining Light Guide in TRIUMF Scintillator Shop

TPB source development at Queen’s

Monitors at DEAP AV radius (85 cm)

Nice uniform coating on witness slide

Three SPC-1 cryogenerators for Snolab

“Stirling Cryogenics has obtained an order from Queen’s University ON Canada for the supply of 3 SPC-1 cryogenerators. These coolers will be used in the cooling/cleaning of the DEAP 3600 project at SNOLAB in Lively ON, Canada and installed at the research facility at a depth of more than 2000 meters. The high efficiency of the Stirling cooler, in combination with several options possible to improve on the process, were of high importance to the customer.”

http://www.d-h-industries.com/news/snolab-order/?newsItemId=1E891928-9807-9295-7A31D0797E0D23A1

News item from Stirling Cryogenics Web Page

3500 liter dewar

Cryocooler and LN2 dewar system – acceptance testing in Eindhoven

Cryocooler and LN2 dewar system – delivery and acceptance on site (April)

Prototype Light Guide / PMT assembly

Custom Injection molded PMT electrical housings

– Purchased & received

Stainless steel band clamps

– Quotes received

– Prototyped

PMTs – Purchased & received

PMT mounts– Drawings approved &

out for quote– Assayed and

selected PVC pipe meeting radiopurity

requirements– PVC materials

purchased & received– Prototyped

Magnetic shielding and specular reflector

– materials selected & quotes received

-- Prototyped

Copper heat short

– final drawings &

preparing for quote

-- PrototypedCourtesy K. Dering

Radon purifier

Internal filter design W. Rau (Queen’s) and E. O’Dwyer M.Sc. thesis

Mechanical Design and Thermal FEAFrom Vance Strickland (TRIUMF/Carleton)

=> See Corina Nantais poster upstairs

Citric acid passivation of process systems

achieved the target emanation rate of ~1 µBq/m (per meter of TIG weld)

Electronics: conceptual design

Courtesy: F. Retiere

Setup @TRIUMF

Courtesy: P.-A. Amaudruz

DEAP-3600 has very competitive physics sensitivity, ~10-46 cm2

Enormous progress past ½ -year

All major contracts are now in place with realistic delivery schedules from suppliers

Steel shell was final public procurement (PMTs, Electronics, Acrylic Vessel Sphere, Light Guide Acrylic, Cryogenic Systems and Dewars, Steel Shell)

Extremely busy period coming up for detector construction, installation at SNOLAB

May 2012: Completed external review of project electronics/trigger

Summary

Courtesy: F. Retiere

Extra Slides

Spartech and RPTA samples – Transparency of DEAP production acrylic

DEAP RPTA acrylic is most transparent we have ever “seen”, close to Rayleigh limit

DEAP Spartech acrylic is also clean, with excess Rayleigh scattering (but we can fix!)

At high wavelengths, only C-H features seen, expected from PMMA itself

PMMA chain segment

Mean wavelength in DEAP: 440 nm

PSD X 100

Attenuation in annealed acrylic (Spartech Production Sheet #11)Temp (oC) Time

(hours)Attenuationlength

No anneal 0 3.3 +/- 0.3 m

95 +/- 8 6 3.4 +/- 0.3 m

110 +/- 8 5 4.5 +/- 0.5 m

130 +/- 10 6 6.5 +/- 0.3 m

124 +/- 2.5 11 6.4 +/- 0.7 m

155 +/- 5 24 8 +/- 1 m

We find that annealing acrylic reduces Rayleigh scattering and “fixes” attenuation

RPT will perform high- temperature anneal of LG blocks

(RPT already has pre- and post-bond anneals, but at lower temperatures)

20” vessel machined at Alberta,Bonded at RPT Colorado

Cooldown at Queen’s (Nantais – M.Sc. and Ward – Post-doc)

20” test vessel cooling tests

From photoelastic strain measurements of the 20” vessel, locked-in stress is low (as expected) < 500 psi

Initial cooldown to -10C; performed photoelastic measurements on cooled acrylic, found stresses < 5 psi / degree (acceptably low and in agreement with cryogenic “dog bone” tests)

DEAP Slow Control / 20” vessel cooldown

Vessel temperature readings

Inlet gas temperature

Will make improvements to cooldown system, cool to 80 K in next few weeks

Will test final TPB source on 20” vessel.

12-05-14 M. Kuźniak 40

Backgrounds with conical cut

±15% PMT QEwith

35deg conical cut

Surface (DEAP-1 Pb210 limit/MC based) and neutron (assay/MC based) backgrounds

B. Cai, E. Vazquez Jauregui, M. Kuzniak

12-05-14 M. Kuźniak 41

DEAP-1 AmBe validation

12-05-14 M. Kuźniak 42

Acrylic attenuation