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