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Construction of the DEAP-3600 Dark Matter detector and first commissioning results.

Tina Pollmann for the DEAP collaboration

WIN2015, Heidelberg, June 10 2015

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The standard model of astronomy puts the composition of the universe at 23% Dark Matter.

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4% Stars, Gas, Planets, etc.

23% Dark Matter

73% Dark Energy

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DEAP is a direct detection experiment, looking for scintillation light produced when an argon nucleus recoils after scattering on a Dark Matter particle.

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Detector

m�

�n�

liquid argon

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The challenges of direct detection: low energy, small signal rate

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m = 100 GeV σ = 10-7 pb exp = 1 ton year

1

10

100

1000

0 10 20 30 40 50 60 70 80 90 100

Even

ts/k

eV

Recoil Energy [keV]

ArgonXenon

Germanium

DEAP-3600

• 1000 kg fiducial mass target volume

• 8 PE/keV lightyield

• < 0.2 background events/year

α γ μ n

Differential dark matter recoil spectrum.

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The argon scintillation pulseshape differs by exciting particle type, allowing PSD against electron-recoil events projected to reach 10-10 at 60 keVr, 8PE/keV.

promptF0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Ev

ents

/0.0

1 w

ide

bin

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10

210

310

410

510

610

-ray eventsγ 7

10×1.7

100 nuclear recoil events

background-like (electron-recoil)

signal-like (nuclear recoil)

DEAP-1 prototype data

γ

Exploiting the singlet (6 ns) and triplet (1.5 μs) lifetime difference.

background (tagged 22Na)

signal (AmBe neutrons)

arXiv: 0904.2930, M. Kuzniak et al., Nuc Phys B Proc Sup 00 (2014) 1–7

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2 km (6800 ft) deep. 0.27 μ/m2/day.

DEAP-3600

SNO+ μ

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Steel shell

Water shielding tank. � 8m

LN2 cryocooler

LAr dewar

Magnetic compensation coils

Calibration source tubes (AmBe, 22Na)

Deck

DAQ racks

Process systems

Calibration source deployment system

μ n

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Liquid Argon (84 K, -188℃) single-phase

3.6 tonnes (total) 1 tonne (fiducial)

Image Credit: Wikipedia

The DEAP-3600 detector.

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Acrylic vessel.

The DEAP-3600 detector.

LAr

n

AV from clean acrylic, assembled underground.

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Radiopurity of MaterialsRadiopurity of Materials Extensive and enormous effort

Acrylic, polymethal-meth-acrylate, sourced, counted in-situ and followed through every step from distillation to thermoforming pure MMA monomer sheets (Thai MMA)

Electropolishing of metal surfaces including interior of the steel shell to reduce radon emanation

Seamless tubing and where unavoidable welds in process system performed with non-thoriated TIG welding to reduce radon emanation

Developed vaporization system for acrylic assays, ultra low background emanation chamber to qualify process systems materials and cleaning methods

<10-19g/g 210Pb, ~ppt U and Th

α

12AV annealed at ~85 C, 5 times.

α

Radon reduced air.

Radon monitored and controlled.

20 30 40 50 60 70 80 90

Tem

pera

ture

[C] Air average

2 6

10 14 18

02/0102/0202/0302/0402/0502/0602/0702/08

Rad

on L

evel

[Bq/

m3 ]

Date (2013, month/day)

α

13Once AV is radon-tight, residual deposits are removed. Resurfacer takes fraction of a mm off the AV's inside.

α

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Acrylic vessel.

The DEAP-3600 detector.

LAr

nTPB wavelength shifter.

15TPB deposition system being installed.

4π thermal evapo- ration source.TPB under UV and visible light.

~μm thickness.

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Acrylic vessel.

Light guide.

The DEAP-3600 detector.

LAr

n

n

50 c

m

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LG acrylic with best transparency, bonded meticulously.

n

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Specular and white reflector covers all surfaces.

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Acrylic vessel.

Light guide.

Filler block.

The DEAP-3600 detector.

LAr

n

nn

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Filler-blocks for extra neutron and heat shielding. n

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Acrylic vessel.

Light guide.

Filler block.

Photo multiplier.

The DEAP-3600 detector.

LAr

n

nn

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255 Hamamatsu 5912 PMTs, oil coupled to LG faces. 71% coverage.

LG

PMT

Copper thermal short

FINEMET magnetic shield

Mount

T ~ -184 C

T > -40 C

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Acrylic vessel.

Light guide.

Filler block.

Photo multiplier.

Cables, insulation.

The DEAP-3600 detector.

LAr

n

nn

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CAEN V1720 250MHz, V140 digitizers

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Acrylic vessel.

Light guide.

Filler block.

Photo multiplier.

The DEAP-3600 detector.

LAr

n

nn

Cables, insulation.

Steel shell.

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Veto PMTs detect Cherenkov light from muons passing through the water thank.

μ n

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Acrylic vessel.

Light guide.

Filler block.

Photo multiplier.

The DEAP-3600 detector.

LAr

n

nn

Cables, insulation.

Steel shell.

Neck, cooling coil.

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Liquid nitrogen storage, gas scrubber and cooling coil.

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Charge[pC]0 10 20 30 40 50

eve

nts/

bin

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510PMTID 0

DataFull fitPedestal1 PE contribution2 PE contribution

DEAP0063CommissioningPreliminary

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4−2−024

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nts/

bin

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PMTID 0DataFull fitPedestal1 PE contribution2 PE contribution3 PE contribution4 PE contribution

DEAP0063CommissioningPreliminary

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4−2−024

PMTID0 50 100 150 200 250

Cha

rge

[pC

]

02468

1012

Fit mean SPE charge

DEAP0063CommissioningPreliminary

LED light injection system used to commission PMTs and DAQ system.

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What if we see nothing?

30plot: J Cooley, arXiv: 1410.4960v2 prediction: C. Strege, arXiv:1212.2636v1

1 10 100 1000 10410!5010!4910!4810!4710!4610!4510!4410!4310!4210!4110!4010!3910!3810!37

10!1410!1310!1210!1110!1010!910!810!710!610!510!410!310!210!1

WIMP Mass !GeV"c2#

WIMP!nucleoncrosssection

!cm2 #

WIMP!nucleoncrosssection

!pb#

CDMS II Ge (2009)

Xenon100 (2012)

CRESST

CoGeNT(2012)

CDMS Si(2013)

EDELWEISS (2011)

DAMA SIMPLE (2012)

ZEPLIN-III (2012)COUPP (2012)

LUX (2013)

DAMIC (2012)

CDMSlite (2013)

DarkSide G2

PICO250-C3F8

DarkSide 50

Xenon1TDEAP3600

LZPICO250-CF3I

LUX 300day

SuperCDMS SNOLAB

SuperCDMS S NOLAB

8BNeutrinos

Atmospheric and DSNB Neutrinos

7BeNeutrinos

COHERENT NEUTRIN O SCATTERING COHERENT NEU

TRI NO SCATTERING COHERENT NEUTRINO SCATTERING

Figure 1: A compilation of WIMP-nucleon spin-independent cross section limits (solid

lines) and hints of WIMP signals (closed contours) from current dark matter experiments

and projections (dashed) for planned direct detection dark matter experiments. Also

shown is an approximate band where neutrino coherent scattering from solar neutrinos,

atmospheric neutrinos and di↵use supernova neutrinos will dominate [13].

results from other experiments. At this point, we do not have conclusiveevidence of a dark matter signal. Hence, it is necessary to have experimentsusing several technologies and a variety of targets located in di↵erent loca-tions to maximize the chances of discovery and to confirm any claimed darkmatter signal. Figure 1 presents the current limits and favored regions ofcurrent experiments and projections of the parameter space we will be ableto explore with the next generation of experiments. As we look forward tothe next decade, it is clear that with a diverse portfolio we will be able toexplore parameter space all the way to the neutrino floor [13].

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DEAP-3600

3 year data run projection for DEAP

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