Development of the LUX detector`s CH3T calibration source and ER

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DEVELOPMENT OF THE
LUX DETECTOR’S CH3T
CALIBRATION SOURCE
AND ER RESPONSE
Richard Knoche
University of Maryland
On behalf of the Lux Collaboration
APS April Meting 2015
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The LUX Detector
• Dual phase liquid xenon TPC at SURF
• 370 kg of xenon (250 kg active)
• 118 kg fiducial volume
• PMT arrays in liquid and gas
• Scintillation (S1) and
ionization (S2) signals
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Internal Calibration Source
• Single beta emitter in energy range of interest (1-10 keVee)
• Low electronegativity so that drift length is unaffected
• Can not attenuate UV scintillation
• Can dissolve into liquid xenon
• Long enough life time to diffuse throughout detector
• Must be removable after use
• Short enough life time to decay away
• Alternatively, something that can be removed through purification
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Tritium as an Internal Source
• Beta emitter with Q-value of 18.6 keV
• Broad spectrum over entire energy range of interest
• 12.3 year half life
• Will diffuse through detector
• Must be purified away
• Sticks to most surfaces
• Teflon, polyethylene, steel, etc.
• Use tritiated methane (CH3T) as an internal calibration
source!
• Low electronegativity
• Inert due to fully saturated carbon-hydrogen bonds.
• Diffusion constant in polyethylene that is 10 times smaller than
hydrogen
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R&D Experiment –
Goals and Setup
• Goal of determining purification efficiency and residual
contamination effects
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R&D ExperimentExperimental Procedure
• Collect background data, inject, purify
Out Gassing Elbow
Background Data
Injection
Purification
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R&D ExperimentResults
• Define purification efficiency
𝐴𝑓𝑡𝑒𝑟 − 𝐵𝑒𝑓𝑜𝑟𝑒
𝑃𝑢𝑟𝑖𝑓𝑖𝑐𝑎𝑡𝑖𝑜𝑛 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 = 1 −
𝑃𝑒𝑎𝑘 − 𝐵𝑒𝑓𝑜𝑟𝑒
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Tritium Injection System for LUX
• Range of injection volumes covering three orders of
magnitude
• No cryopumping required
Flow Through
Expansion Volumes
Tritiated
Methane
Source
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Purification Rate
• Verified ability to remove natural methane
• Natural methane purification time constant and CH3T time constant
agree very well
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Distribution of Events
• Tritiated methane is spatially uniform
0
50
drift time (ms)
100
150
200
250
300
0
100
200
300
400
2
radius squared (cm )
500
600
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ER Band
• Tritiated methane calibrates the ER band over the entire
WS energy range
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Discrimination
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Other Physics
• Fiducial Volume Mass
• Detector Threshold
• Light Yield and Charge Yield
• G1 and G2 for Energy Reconstruction
• Recombination Fluctuations and Detector Resolution