deap-1 for snolab2009 report to snolab2009 chris jillings on behalf of the deap-1 team

DEAP-1 for SNOLAB2009

Report to SNOLAB2009

Chris Jillings

on behalf of the DEAP-1 team


Timeline• July 4, 2008 Fill

– Gen 1 clean chamber

– Topup: Radon spike

– Background studies

• Jan 2009 - March 2009– Emanation measurements

– Improved design/manufacture of chamber

• March 19, 2009 Fill– Gen 2 clean chamber

– Radon trap

– Install new DAQ

– Strike

– PSD running

– Background studies

• Future


Improvements Since October 2008

• Backgrounds Reduced Factor of 10– And much better understood

• DAQ/Electronics – Installed by TRIUMF team (F. Retiere/P.-A.

Amaudruz)– Throughput ~x10 higher– Using hardware that will be used for DEAP-3600

• PSD improved


Zfit Calibration

Zfit is a calibrated measure of position in the detector.


Background Rates

July 4, 2008 Run2-3 mHz steady state

Top-up added large 222Rn spike

Used to develop U-chain tags

0

10


Emanation Measurement


Emanation Measurement

• While warm treated DEAP-1 as emanation chamber– Pumped to high vacuum– Allowed to emanate for many days– 134 +/- 19 Rn emanated/day– Repeated measurement with DEAP-1 chamber removed

and blanked off: 6 +/- 4 Rn atoms/day– Also did background (“zero exposure”) emanations.

• Emanation results consistent with all Radon coming from chamber.

• Emanation of reflective paint at Queen’s was equal within error to emanation from all chamber.


Improvement DetailsGeneration I: 2008• Produced in glovebox• Sanded surfaces

– ~20 particles/cm2 left on acrylic

– From 175 to 78000 mBq/kg U depending on brand/batch

– 0.01 to 3 mBq Rn in DEAP-1

• TPB on inner surface– <4 mBq/kg U/Th

• Exposure during evaporation– ~4 bgnd events/year

• Sealing of vacuum vessel– Possible admission of Rn in

shipping

Generation II: 2009• Improved glovebox/Rn

monitoring• Sanding Improvements

– Used clean sandpaper– High-pressure rinse inside

glove box

• As before

• As before

• Vacuum chamber was leak tested in glove box and filled with Rn-free air.


Improvement Details (2)Generation I: 2008• 3 failed fills allowing unknown

quantity air into DEAP-1

• Radon in argon during fill– Unknown how much gets

through cooling coils– Could have ~1 day exposure to

high Radon loads

• Background analysis– Offline, interpretations

developed over weeks and months.

– Data show surface rates measurable before fill

Generation II: 2009• Procedures improved.

– Venting through bubblers

– Last fills and top-ups worked

• Radon filter in DEAP-1– Cold carbon trap Rn just above

Argon boiling point

– Prototype built. Tested.

– Installed prototype for Mar16 fill

• Near-Online and Automatic Analysis


Radon Filter

Prototype charcoal filter operating temperature -110C.

No measurable Rn punch through in tests at Queen’s.

Used for March 19 fill.

Similar but larger device to be used on DEAP-3600.


Background Rates

July 4, 2008 Run2-4 mHz steady state

Top-up added large 222Rn spike

Used to develop U-chain tags

March 19, 2009 Run0.2 to 0.4 mHzNo initial spike


U Chain: 222Rn and short-lived daughters

Model: 222Rn and 218Po decay in LAr (100% eff detection).

214Po is on surface (50% eff det).


Th Chain: 220Rn to 216Po to 212Pb

Seen at correct energy with same z position in detector

30 events in 236 hrs (Mar 19 run)

t<1s


Thorium Chain: 212BiPo (300 ns)


Backgrounds

Rate from coincidence tag(40 events each of 222Rn + 220Rn)

10 days livetime


Backgrounds in DEAP-1Current background rate in ROI (120-240 pe) is 0.15 mHz

Need absolute background of < 2 nHz for DEAP-3600, or 2 micro-Hz before position reconstruction for surface events


Backgrounds

• Clear evidence for Rn from U and Th chain based on alpha-coincidence tags

• Improving calibrations of light yields in TPP.• To improve understanding of all alpha events

below full-energy (in Argon) alpha peaks.

• This could include 210Po (daughter of 210Pb).


PSD

Dataset Events

x108

Days Days

to 108

Surface arXiv:0904.2930

0.17 ~20 120

July 4, 2008

0.22 12 55

Mar 16,

2009 New DAQ

0.44

8.8 20 (Could be

halved with hotter

source.)

Mar 16,

2009

~0.61 12.3 20

Faster DAQ: >108 events in 22 daysData sets so far: 12x10-9 demonstrated

7x10-9 after analysis of all events on disk.


Prototype of DEAP-3600 DAQ

• Installed and maintained by TRIUMF group.

• Allows data rates of ~15 Mbytes/sec

• ~600 events * 2 channels * 4000 12-bit samples/ch

• CAEN V1720 WFD• MIDAS DAQ (well

supported at TRIUMF)• Scalers to be implemented

V1720Struck scaler

Linux computer


Future

• DEAP-1 is our most sensitive tool for understanding backgrounds.

• We are using DEAP-1 as a test bench for process systems and to measure activities in acrylic surfaces and TPB.

• We are using DEAP-1 to prototype and test electronics and DAQ.

• We are requesting to run DEAP-1 at SNOLAB for the next 2 to 3 years. We understand that a relocation may be necessary.


• end


Scientists who have worked u/g on DEAP1

Mark Boulay1, Bei Cai1, Jeff Lidgard1, Ian Lawson2, Kevin Graham3, Fraser Duncan2, Chris Jillings2, Paradorn Pasuthup1, Noel Gagnon2, Peter Skensved1, Ueshima Kota4, Hugh Lippincott7, Kiyoshi Masui1, Luc Gatien2, Rafael Hakobyan5, Kevin Olsen5, Shawn Ligocki1, Takashi Iida4, Shawn Compton3, Victor Golovko1, Cameron Hurst1, Michael Ronquest6, Reyco Henning6, Perry Young1, Zach Fairchild2, Brian Wong2, TJ Robotham2, Bruce Cleveland2, Eoin Odwyer1, Oleg Chekvoretz2, Eric Vazquez2,Marcin Kuzniak1, Fabrice Retiere8,Pierre-Andre Amaudruz8, Rob Bark2, Corina Nantais1, Aline Trosset1, Berta Beltran5, 1: Queen’s 2: SNOLAB 3: Carleton 4: ICRR/Honda Canada

Fellow 5: U. Alberta 6: U.N.C. 7:Yale 8: TRIUMFPhD, Graduate Student, Undergraduate student or degree

deap-1 for snolab2009 report to snolab2009 chris jillings on behalf of the deap-1 team

Documents