Status of the DEAP-3600 Search Experiment Ben Broerman for the DEAP collaboration Queen’s University [email protected]

Introduction Detector Schematic - The Dark matter Experiment using Pulse-shape discrimination (DEAP-3600, Fig. 1) located at SNOLAB in Sudbury, Canada. Glove box - 3.6 tonnes of liquid argon (LAr) in a spherical acrylic vessel 85 cm in Central support assembly radius, coated in wavelength shifter tetraphenyl butadiene (TPB) (Deck elevation) - 255 inward-facing 8-inch R5912 photomultiplier tubes (PMTs) coupled Steel shell neck through 50 cm light guides (LGs). (Outer neck)

- LAr maintained with 2 m neck cooling coil Inner neck (green) Vacuum jacketed neck (orange) - Housed in spherical pressure vessel inside 8 m diameter water veto tank. Cooling coil - PSD and background control allow for a targeted spin-independent sensi- tivity of 10−46 cm2 for a 100 GeV/c2 WIMP mass. Acrylic flow guides

48 veto PMTs

255 PMTs & light guides

Acrylic vessel

Steel shell

Acrylic vessel, after bonding of the LGs 3600 kg liquid argon

Filler blocks DEAP-3600 projected spin independent sensitivity for a background-free Foam blocks behind 3 tonne-year exposure along with experimental Limits from DarkSide-50 PMTs and filler blocks (2015), Xenon-100 (2012), PandaX (2016), and LUX (2016). Bottom spring support Signal Detection Figure 1: Schematic of the DEAP-3600 detector. The inner surface of the AV is coated in TPB (not shown). DEAP-3600 after installation of PMTs

Energy Argon Deposition Dimer in LAr Formation Sources of Background and Control

singlet = 6 ns (nuclear recoil) Control Target triplet = 1.6 µs (electron recoil) radiopure acrylic and TPB, TPB 2 128 nm Surface α’s resurfacing, < 0.2 µBq/m wavelength photon fiducialization shifting Inside the water tank, steel shell closed, veto PMTs and calibration tubes installed.

430 nm PMT 50 cm LGs, photon signal HDPE filler blocks, readout Neutrons and material se- < 2 pBq/kg lection to reduce 13C(α, n)

Cold charcoal trap, Schematic of the Resurfacer used to Rn in Ar low emanation < 1.4 nBq/kg sand the inner acrylic surface. Evaporation source for the TPB wavelength shifter. A 3 µm 0.5 mm of acrylic was removed to thick coating was applied through vacuum deposition. components reduce Rn progeny on the inner 39 surface. After resurfacing, the clean Ar PSD < 2 pBq/kg acrylic was kept under vacuum or Pulse Shape Discrimination (PSD) 3 tonne-year exposure in ROI < 0.6 events boil-off N2.

T (keV ) eff ee 0 20 40 60 80 100 120 140 160 1 0.9 0.8 0.7 Current Status: Liquid Fill 0.6 0.5 prompt F 0.4 - Mass in detector and 0.3 triplet lifetime (left) 0.2 0.1 indicate stability and a 0 0 50 100 150 200 250 300 350 400 450 500 clean fill Number of photoelectrons - Current mass: 2800 kg DEAP-1 calibration data with AmBe (top band, n) and Nuclear and electromagnetic recoil PMT traces, 22 Na (lower band, γ). Singlet/triplet lifetime differences lead to prompt region (1st 150 ns) shaded. the two recoil bands. - Taking DM physics PromptPE data soon Fprompt = TotalPE