1 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 2 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 3 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 4 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 5 R&D Experiment – Goals and Setup • Goal of determining purification efficiency and residual contamination effects 6 R&D ExperimentExperimental Procedure • Collect background data, inject, purify Out Gassing Elbow Background Data Injection Purification 7 R&D ExperimentResults • Define purification efficiency 𝐴𝑓𝑡𝑒𝑟 − 𝐵𝑒𝑓𝑜𝑟𝑒 𝑃𝑢𝑟𝑖𝑓𝑖𝑐𝑎𝑡𝑖𝑜𝑛 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 = 1 − 𝑃𝑒𝑎𝑘 − 𝐵𝑒𝑓𝑜𝑟𝑒 8 Tritium Injection System for LUX • Range of injection volumes covering three orders of magnitude • No cryopumping required Flow Through Expansion Volumes Tritiated Methane Source 9 Purification Rate • Verified ability to remove natural methane • Natural methane purification time constant and CH3T time constant agree very well 10 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 11 ER Band • Tritiated methane calibrates the ER band over the entire WS energy range 12 Discrimination 13 Other Physics • Fiducial Volume Mass • Detector Threshold • Light Yield and Charge Yield • G1 and G2 for Energy Reconstruction • Recombination Fluctuations and Detector Resolution