Status of the DEAP-3600Dark Matter Search Experiment
Ben Broerman for the DEAP collaborationQueen’s [email protected]
Introduction
- The Dark matter Experiment using Argon Pulse-shape discrimination
(DEAP-3600, Fig. 1) located at SNOLAB in Sudbury, Canada.
- 3.6 tonnes of liquid argon (LAr) in a spherical acrylic vessel 85 cm in
radius, coated in wavelength shifter tetraphenyl butadiene (TPB)
- 255 inward-facing 8-inch R5912 photomultiplier tubes (PMTs) coupled
through 50 cm light guides (LGs).
- LAr maintained with 2 m neck cooling coil
- Housed in spherical pressure vessel inside 8 m diameter water veto tank.
- PSD and background control allow for a targeted spin-independent sensi-
tivity of 10−46 cm2 for a 100 GeV/c2 WIMP mass.
DEAP-3600 projected spin independent sensitivity for a background-free3 tonne-year exposure along with experimental Limits from DarkSide-50(2015), Xenon-100 (2012), PandaX (2016), and LUX (2016).
Signal Detection
EnergyDeposition
in LAr
ArgonDimer
Formation
singlet = 6 ns (nuclear recoil)triplet = 1.6 µs (electron recoil)
128 nmphoton
TPBwavelength
shifting
430 nmphoton
PMTsignal
readout
Acrylic vessel, after bonding of the LGs
DEAP-3600 after installation of PMTs
Inside the water tank, steel shell closed,veto PMTs and calibration tubes installed.
Evaporation source for the TPB wavelength shifter. A 3 µmthick coating was applied through vacuum deposition.
Pulse Shape Discrimination (PSD)
Number of photoelectrons0 50 100 150 200 250 300 350 400 450 500
pro
mp
tF
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
)ee
(keVeffT
0 20 40 60 80 100 120 140 160
DEAP-1 calibration data with AmBe (top band, n) and22Na (lower band, γ). Singlet/triplet lifetime differences lead tothe two recoil bands.
Nuclear and electromagnetic recoil PMT traces,prompt region (1st 150 ns) shaded.
Fprompt = PromptPETotalPE
Detector Schematic
Glove box
Central support assembly(Deck elevation)
Steel shell neck(Outer neck)
Inner neck (green)Vacuum jacketed neck (orange)
Cooling coil
48 Muonveto PMTs
255 PMTs& light guides
Acrylic vessel
Filler blocks
Bottom spring support
3600 kgliquid argon
Foam blocks behindPMTs and filler blocks
Acrylic flow guides
Steel shell
Figure 1: Schematic of the DEAP-3600 detector. The inner surface of the AV is coated in TPB (not shown).
Sources of Background and Control
Control Target
Surface α’s
radiopure acrylic
and TPB,
resurfacing,
fiducialization
< 0.2 µBq/m2
Neutrons
50 cm LGs,
HDPE filler blocks,
and material se-
lection to reduce13C(α, n)
< 2 pBq/kg
Rn in ArCold charcoal trap,
low emanation
components
< 1.4 nBq/kg
39Ar PSD < 2 pBq/kg
3 tonne-year exposure in ROI < 0.6 events
Schematic of the Resurfacer used tosand the inner acrylic surface.
0.5 mm of acrylic was removed toreduce Rn progeny on the inner
surface. After resurfacing, the cleanacrylic was kept under vacuum or
boil-off N2.
Current Status: Liquid Fill
- Mass in detector and
triplet lifetime (left)
indicate stability and a
clean fill
- Current mass: 2800 kg
- Taking DM physics
data soon
Recommended
