calibration of single phase liquid argon detectors
TRANSCRIPT
Calibration of Single Phase Liquid Argon Detectors
Kimberly J. PalladinoMIT
MiniCLEAN Collaboration
1Tuesday, July 24, 2012
Outline
Single Phase Liquid Argon technique
Calibration Goals
Internal calibration sources
External gamma sources
External neutron sources
Optical calibration
2Tuesday, July 24, 2012
Single Phase Liquid Argon
Scintillation in LAr at 128 nm, requires wavelength shifter, TPB, to allow PMT detection
Pulse shape discrimination (PSD) based on triplet lifetime of 1.6 us and singlet lifetime of 6 ns
Fprompt, PSD variable, low (~0.3) for electronic recoils, and high (~0.8) for nuclear recoils
Position reconstruction based on charge distribution and timing in larger detectors
3Tuesday, July 24, 2012
Calibration goals
Internal Sources
Gamma Sources
Neutron Sources
Light Injection
Sing
le P
E
Ener
gySc
ale
Ener
gyRe
solu
tion
Posi
tion
Reco
n.
PSD
Surf
ace
Even
ts39
Ar/
PSD
Leak
age
Neu
trons
Nuclear recoilsElectronic recoils4
Tuesday, July 24, 2012
39Ar
Naturally occurring 39Ar in atmospheric argon with activity of 1 Bq/kg
First forbidden beta decay with analytically defined spectral shape
Spectrum known to 1% down to 10 keV
Endpoint at 565 keV
Half-life of 269 years
Uniform distribution in detector
Continuous calibration
5Tuesday, July 24, 2012
39Ar: Energy Scale
Triplet tail from 39Ar allows constant monitoring of the single photo-electron spectrum and every individual PMT’s gain
Continuous detector health, including triplet lifetime
MiniCLEAN will see ~800 kHz of 39Ar
Light-yield measured in going from PE to keVee
1 day gives a statistical LY measurement to better than 1%
6Tuesday, July 24, 2012
39Ar: Position Reconstruction
Uniformity gives r2 relation in differential rates
Allows daily studies of radial bias and position reconstruction
Large datasets outside WIMP ROI
Energy dependent studies
7Tuesday, July 24, 2012
39Ar: Pulse Shape DiscriminationProbe of the electronic recoil rejecting pulse shape discrimination variable (Fprompt) with all events outside the fiducial volume
But surface alpha and neutron events will have to be taken into account
MiniCLEAN planning an 39Ar Spike, 5-10x natural abundance after Dark Matter run to demonstrate PSD in larger detectors and investigate potential backgrounds
Fast reactor irradiation of KF/KCl utilizing 39K(n,p)39Ar as is done in radiometric dating
UV ablated muscovite@ NM GeochronologyResearch Laboratory
8Tuesday, July 24, 2012
83Krm
83Rb (trapped in charcoal) decays with a half-life of 86.2 days to 83Krm 75% of the time, which, as a Noble gas flows into the detector
83Krm subsequently emits two conversion electrons with a total energy of 41.5 keV and a half-life of 1.83 hours
Calibrates energy as a function of position -> no sign of freeze out in MicroCLEAN
Planned calibration for KATRIN arXiv.org:0109033v1 and also studied for LXe detectors Kastens et al. JINST 5(2010) P05006 and Manalaysay et al. Rev. Sci.Instrum 81 (2010) 073303
Lippincott et al. Phys.Rev.C81:045803. 2010. arXiv:0911.5453.
83Krm energy spectrum after background subtraction
in MicroCLEAN
9Tuesday, July 24, 2012
External Gamma SourcesAdditional energy and position calibration, especially for high radius events
Tagged sources allow reduction of the 39Ar background during calibration
DEAP-3600 can study neck region events
22Na: e+ and 1.274 MeV γ used by both MicroCLEAN and DEAP-1, MiniCLEAN tagged source
60Co: 1.17 and 1.33 MeV γ DEAP-3600 tagged source
Also considered:
137Cs: 662 keV γ
57Co: 122, 136, 692 keV γ
Isotopes DEAP-3600
MiniCLEAN
10Tuesday, July 24, 2012
Neutrons: D-D generatorNuclear recoil PSD and energy calibration, test neutron tagging and verify simulation physics
Primary calibration through dd-interaction
Using Schlumberger MiniTron allowing pulsed and DC mode operation
At 40kV, the neutron yield is 103 n/uC resulting in 105n/s at 50 uC
11Tuesday, July 24, 2012
D-D Neutron Simulations
MiniCLEAN studies show 1.1% of generated neutrons in fiducial volume and energy ROI, lower for larger, acrylic shielded DEAP-3600
Liskien & Paulsen (1973)J. Walding12.5-25 keVee, r<295 mm 12.5-25 keVee, r>295 mm
12Tuesday, July 24, 2012
D-D System
Power supplies and control electronics operating since 2010
Moving from prototype canister (shown) to final canister
Deployment system under construction at RHUL. Moveable with size of 1.0m x 0.8m x 2.8m
13Tuesday, July 24, 2012
Neutrons: Hot PMT
MiniCLEAN pursuing a “Hot PMT” calibration source to reproduce most dangerous neutron background
Will mix 5.3 g of 238U and 16g of 232Th in melted PMT glass to produce 1 n/s
Tagged source with scintillator to see alpha, n de-excitation gammas
Currently prototyping with 2 lbs of uranium borosilicate with 16 g (1.8%) 238U
pre WW-II with more daughters, but expected rate of 3 n/s
M. Akashi-Ronquest
14Tuesday, July 24, 2012
Optical Calibration: DEAP-3600Optics before and after TPB deposition
LEDball in diffuser, lowered through neck: 425 nm before TPB deposition, 250 nm after
Optics stability, timing
Distributed light by fibers to PMTs ,light will reflect into the detector
Light leakage from neck: laser light injection
15Tuesday, July 24, 2012
Optical Calibration: MiniCLEANProbe visible and UV optics, and surface event position reconstruction
6 UV (254 nm) and 6 Blue (465 nm) LEDs, in the LAr with fibers running to face of pentagonal lightguides
Kapustinsky pulser allows fast pulses as expected from prompt argon scintillation
20 ns trigger pulse
Kapustinsky trigger pulse
16Tuesday, July 24, 2012
CalibratorsDEAP-3600
RHUL: dd-neutrons,
light injecton
RAL: gammas, 83Krm
Sussex: light injection
Queen’s: 39Ar
SNOLab: 39Ar, gammas
MiniCLEAN
LANL: 39Ar, gammas, Hot PMTs, 83Krm
MIT: dd-neutrons, 83Krm
RHUL: dd-neutrons
UNM: light injection
17Tuesday, July 24, 2012
Conclusion
Both DEAP-3600 and MiniCLEAN have developed calibration plans with multiple handles on each experimental parameter
39Ar, though a background, is an excellent calibration source too!
Both experiments will have exciting year’s as they build, and calibrate, the detectors!
18Tuesday, July 24, 2012
Collaborations
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20Tuesday, July 24, 2012