DM-Ice Reina Maruyama University of Wisconsin - Madison SNOWMASS - - PowerPoint PPT Presentation

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DM-Ice Reina Maruyama University of Wisconsin - Madison SNOWMASS - - PowerPoint PPT Presentation

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DM-Ice Reina Maruyama University of Wisconsin - Madison SNOWMASS 2013: Cosmic Frontier Workshop March 6 - 8, 2013 http://www.physics.wisc.edu/~maruyama/ Wednesday, March 6, 13 1. Experiment Status and Target Mass Currently in Operation:

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SLIDE 1

DM-Ice

Reina Maruyama

University of Wisconsin - Madison

SNOWMASS 2013: Cosmic Frontier Workshop March 6 - 8, 2013 http://www.physics.wisc.edu/~maruyama/

Wednesday, March 6, 13

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SLIDE 2

Snowmass - March 2013 DM-Ice

  • 1. Experiment Status and Target Mass

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Currently in Operation: DM-Ice17

17 kg of NaI(Tl), operation since 2011 Funding: NSF-Polar Programs & NSF-CAREER for R&D First results expected in Spring 250 kg of ultra-pure NaI(Tl) Proposed deployment: Dec. 2015

Proposed Full-Scale: DM-Ice

Wednesday, March 6, 13

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SLIDE 3

Snowmass - March 2013 DM-Ice

  • 2. Fiducial Target Mass

DM-Ice diameter is limited to ~65 cm by the ice drill. DM-Ice17: 2 modules (pressure vessels) 5” dia x 5” long, 1 crystal / module total mass: 17 kg of NaI(Tl) DM-Ice: 2 modules 5” dia x 15” long, 7 crystals/module total mass: 250 kg of NaI(Tl) Multi-crystal events veto.

3

Wednesday, March 6, 13

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SLIDE 4

Snowmass - March 2013 DM-Ice

Going from DM-Ice17 to DM-Ice

  • Background goal: < 1 cpd/keVee/kg in 2 - 10 keVee (factor of 10 reduction)
  • Contamination levels in DM-Ice17 estimated from in-ice data and radio-

assay, verified by simulation

  • Dominant background in DM-Ice17: 40K & 210Pb in the crystals
  • Surrounding ice is extremely clean, drill ice is clean enough
  • Ultra-clean crystals are under development (see F

. Calaprice’s talk)

  • Cleaner PMT, Pressure Vessel, & Quartz are available
  • Direct muon interaction contribute O(10-5) below other backgrounds
  • Muon monitor & tag with IceCube
  • 3. Backgrounds

4

DM-Ice17 DAMA

natK

500 ppb < 20 ppb

232Th

50 ppt 0.5 - 7.5 ppt

238U (upper part of

chain) 7.5 ppt 0.7 - 10 ppt

238U (below Pb-210)

2 mBq/kg 5 - 30 μBq/kg Crystal contamination in DM-Ice17 & DAMA

preliminary

Alpha region in DM-Ice17 vs. Simulation

Wednesday, March 6, 13

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SLIDE 5

Snowmass - March 2013 DM-Ice

Backgrounds and Calibration: DM-Ice17

5

Energy [keV] [Counts/keV/7.5 kg/718 hrs]

583 keV (208Tl from 232Th) 1173 & 1333 keV (60Co) 352 keV (214Pb from 238U) 239 keV (212Pb from 232Th)

In-ice data, DM-Ice17, Crystal-1 Boulby

  • Energy = integral(waveform)
  • Detectors calibrated using internal

lines

  • Spectra compared & verified with

source calibration at Madison and Boulby

  • 207Bi (569.7 & 1063.66 keV)
  • 60Co (122.06 & 136.5 keV),
  • 57Co (1173.34 & 1332.50 keV)
  • Calibration stable over >18 months

Madison

1460 keV (40K) 609 keV 214Bi from 238U)

Wednesday, March 6, 13

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SLIDE 6

Snowmass - March 2013 DM-Ice

Low Energy Spectrum

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210Pb&(46.5&keV)&+&129I&(40&keV) 125I&(67.3&keV) 125I&X6rays

125I (67.3 keV) Peak counts v. time

––– July 2011 ––– April 2012

cpd/keV/kg keV

210Pb&on&surface?&(12&keV)

  • 7 - 10 cpd/keVee/kg between 8 - 30 keVee.
  • Low energy region calibrated with internal lines from Pb-210, I-125, & I-129
  • Cosmogenic activation of 125I observed with T1/2 = 59.4 days
  • K-40 line at 3.2 keV also visible.

Energy Spectrum < 150 keV

Wednesday, March 6, 13

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SLIDE 7

Snowmass - March 2013 DM-Ice

  • 4. Detector Discrimination
  • We currently use PSD to eliminate instrumental effects, e.g. “thin-pulses” that

seem to originate in the PMTs in the ROI, but not used in physics events.

  • At higher energies, it is possible to use PSD discriminate between gammas,

alphas, and nuclear recoil. In the energy region of interest, PSD is not effective and will not be used.

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center xtal, pmt-0 center xtal, pmt-1

ADC Time (ADC units, 600 ns window) ATWD ch0

Physics Events >100 keV <100 keV Instrumental Events “Thin Pulses” EM Interference

Wednesday, March 6, 13

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SLIDE 8

Snowmass - March 2013 DM-Ice

  • 5. Energy Threshold

DM-Ice Goal:

  • < 2 keVee threshold

DM-Ice17:

  • Analysis threshold: 8 keVee is robust,

analysis in progress down to ~ 2 keVee with single crystals

  • Light collection: 5 - 6 pe/keV
  • Each PMT triggered at fraction of pe

8

––– July 2011 ––– April 2012

cpd/keV/kg keV

Energy Spectrum < 150 keV

pedestal 1pe single&photo6electron&spectrum

Wednesday, March 6, 13

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SLIDE 9

Snowmass - March 2013 DM-Ice

  • 6. Sensitivity versus WIMP mass

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500 kg•year NaI detector sensitivity

(2 - 4 keV) with 1, 2, and 5 dru background

  • DM-Ice goal: test DAMA’s claim for detection
  • f DM annual modulation
  • Use the same target mass: NaI(Tl)
  • 500 kg-yr with (2-DAMA years)
  • < 5 cpd/keV/kg (DAMA: ~1 cpd/keV/kg)
  • Decouple possible seasonal effects from

dark matter modulation

arXiv:1106.1156

Wednesday, March 6, 13

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SLIDE 10

Snowmass - March 2013 DM-Ice

  • 7. Experimental Challenges
  • Development of Ultra-pure NaI powder

and crystals by ANAIS, Princeton, KIMS, DM-Ice... (see also F . Calaprice’s talk)

  • ultra-pure developed
  • crystals grown w/ ~40 ppb potassium
  • currently tracking down 210Pb
  • Maintaining the capability to drill 70cm
  • dia. 2500 m deep holes at the South Pole
  • 86 holes, up to 20 holes, in one

season demonstrated by IceCube

  • Most of the equipment still at S. Pole

but slowly being reassigned

  • Key personnel still available

10 Drill & Deployment Towers IceCube Drill - 3/4/2013 Blaise Kuo Tiong R&D Crystals ANAIS Collaboration, Dec. 2012

Wednesday, March 6, 13

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SLIDE 11

Snowmass - March 2013 DM-Ice

  • Commissioning and optimization from Feb - June 2011
  • Data run since June 2011
  • 99.8% uptime for most weeks with well defined down time for occasional

power cycling + pedestal and dark noise runs

  • 8. Annual Modulation

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7 days/point

Detector Uptime: DM-Ice17

Wednesday, March 6, 13

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SLIDE 12

Snowmass - March 2013 DM-Ice

Detector Monitoring: DM-Ice17

data run data run

  • Monitored quantities:
  • Temperature of the boards
  • ~10°C above surrounding ice
  • Fast (2-3 weeks) decrease

during freeze-in

  • slower decrease over a few

months after freeze-in

  • Pressure follows similar trend as

temperature (ADC resolution limited)

  • Values recorded every 2 sec.

before April 2012. Every 60 sec. since April 2012.

Wednesday, March 6, 13

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SLIDE 13

Snowmass - March 2013 DM-Ice

  • High voltage of each PMT
  • commissioning run until day 167
  • Single PMT total trigger rate
  • General decay over time
  • single trigger rate variation seems

mostly in the noise

  • coincidence trigger rate at low

energy under study

data run data run change monitoring frequency Trigger rate (individual PMT)

Detector Monitoring: DM-Ice17

Wednesday, March 6, 13

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SLIDE 14

Snowmass - March 2013 DM-Ice Northern Hemisphere Gran Sasso DAMA/Libra 250kg running Gran Sasso Princeton-NaI R&D Canfranc ANAIS 250 kg starting in 2014? PICO-LON KIMS etc... Southern Hemisphere South Pole DM-Ice 17 kg running R&D for 250 kg ANDES Lab (proposed) expected start 2018 2017

ice rock

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Several Groups conducting ultra-pure crystal with several vendors to go to the full scale

under development

DM-Ice:

  • NaI dark matter search in an entirely different environment
  • South Pole offers:
  • Ultra-clean and ultra-stable environment
  • Seasonal variation unambiguously different from dark matter modulation
  • IceCube offers muon monitoring and veto as well as experience
  • NSF-run South Pole Station for logistical support
  • 9. Unique Capabilities

Wednesday, March 6, 13

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Snowmass - March 2013 DM-Ice

  • 10. Determining WIMP properties and

astrophysical parameters

  • DAMA sees annual modulation at 9σ

✴... but is it dark matter?

  • 15 years since first claim of observation
  • f modulation
  • alternate hypotheses (backgrounds)

raised but no definitive answers

  • NaI in northern hemisphere will test

background hypotheses

  • Southern hemisphere experiment test

background AND dark matter hypotheses

  • As DM experiments grow bigger, there

will be many unexplained near-threshold events.

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Time to figure out what’s going on in DAMA.

  • J. Hall, Aspen 2012

Wednesday, March 6, 13

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SLIDE 16

Imagine...& a&world&where&we&know&the&origin&of&DAMA’s&signal.

Wednesday, March 6, 13

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SLIDE 17

Snowmass - March 2013 DM-Ice

University of Wisconsin – Madison Reina Maruyama, Francis Halzen, Karsten Heeger, Albrecht Karle, Matthew Kauer, Carlos Pobes, Walter Pettus, Zachary Pierpoint, Antonia Hubbard, Bethany Reilly University of Sheffield Neil Spooner, Vitaly Kudryavtsev, Dan Walker, Matt Robinson, L. Thompson, Sam Telfer, Calum McDonald University of Alberta Darren Grant University of Illinois at Urbana-Champaign Liang Yang Fermilab Lauren Hsu

DM-Ice Collaboration

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Shanghai Jiao Tang University Xiangdong Ji, Changbo Fu Penn State Doug Cowen, Ken Clark NIST-Gaithersburg Pieter Mumm University of Stockholm Chad Finley, Per Olof Hulth, Klas Hultqvist, Christian Walach DigiPen Charles Duba, Eric Mohrmann Boulby Underground Science Facility Sean Paling SNOLAB Bruce Cleveland *Special Thanks to the IceCube Collaboration*

Wednesday, March 6, 13