Proportional Light in a Dual Phase Xenon Chamber Elena Aprile as long as the XENON Coll

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Proportional Light in a Dual Phase Xenon Chamber Elena Aprile as long as the XENON Coll

Biddell, Adam, General Manager has reference to this Academic Journal, PHwiki organized this Journal Proportional Light in a Dual Phase Xenon Chamber Elena Aprile as long as the XENON Collaboration Physics Department in addition to Columbia Astrophysics Laboratory Columbia University, New York The XENON Collaboration Columbia University Elena Aprile (PI),Karl-Ludwig Giboni ,Chuck Hailey ,Pawel Majewski, Kaixuan Ni in addition to Masaki Yamashita Rice University Uwe Oberlack ,Omar Vargas Yale University Daniel McKinsey Princeton University John Kwong, Tom Hartmann, Kirk McDonald, Nathaniel Ross, Tom Shutt Brown University Richard Gaitskell, Peter Sorensen, Luiz DeViveiros Lawrence Livermore National Laboratory William Craig, Norm Madden University of Florida Laura Baudis The XENON Dark Matter Experiment Dual Phase Liquid/Gas Xe The XENON design is modular Multiple 3D position sensitive LXeTPC modules, each with a 100 kg active Xe mass -> 1-tonne scale experiment. The 100 kg fiducial LXe volume of each module is shielded by additional 50 kg LXe. Active shield very effective as long as charged in addition to neutral background rejection Proposed Sept. 2001. Funded Sept. 2002. Currently – R&D towards 10 kg prototype. Proposal as long as XENON100 submitted Oct. 2003

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~ 1 event/100 kg/yr Edelweiss (June 2002) ~0.25 event/kg/d ~1 event/kg/yr http://dmtools.berkeley.edu XENON Dark Matter Sensitivity Liquid Xenon as long as Dark Matter WIMPs High mass Xe nucleus (A ~131) good as long as WIMPs S.I. Int. ( s ~A2 ) Odd Isotopes with large spin-dependent enhancement factors High atomic number (Z=54) in addition to density (r=3g/cc) of liquid state good as long as compact in addition to flexible detector geometry Production in addition to purification of Xe with 1ppb O2 in large quantities as long as tonne scale experiment. “Easy” cryogenics at – 100 C. Excellent ionizer in addition to scintillator with distinct charge/light ratio as long as electron/nuclear energy deposits as long as background rejection No long-lived radioactive isotopes. 85Kr reducible to ppt level Electron vs Nuclear Recoil Discrimination in XENON Drift Time E anode e- grid cathode ~1s ~40ns Nuclear recoil from WIMP Neutron Electron recoil from gamma Electron Alpha Gas Liquid Measure both direct scintillation(S1) in addition to charge (proportional scintillation) (S2) Proportional scintillation depends on type of recoil in addition to applied electric field. electron recoil S2 >> S1 nuclear recoil S2 < S1 but detectable if E large Outline Operation of a single phase xenon chamber with PMT in LXe Chamber description, experiment setups Charge collection in addition to electron lifetime Light in addition to charge correlation Light collection improvement with PTFE Operation of a dual phase xenon chamber Operation technique, chamber parameters Direct in addition to proportional light wave as long as ms, method of analysis Proportional light spectrum Properties of electron emission in addition to proportional scintillation Electron emission yield with extraction field Proportional light yield as a function of field in addition to pressure Ratio between direct in addition to proportional light Single phase LXe Detector with Charge in addition to Light Vg Vc Bi-207 PMT LXe Anode Grid Cathode E Q 1cm between Grid in addition to Cathode, 5mm between Anode in addition to Grid. Gamma rays (570keV in addition to 1064keV) in addition to electrons (554keV in addition to 976keV) from Bi-207 deposited on the center of Cathode. Direct scintillation light read out by PMT (Hamamatsu R6041) immersed in LXe. Ionization electrons read out by charge-sensitive pre-amplifier. Charge collection 570keV 1064keV Charge collection calculated assuming W- value of 15.6 eV as long as LXe. With PMT in addition to its HV divider in the LXe, a good charge collection was achieved after several cycles of purification in addition to baking of chamber. Electron lifetime Event drift time defined with respect to the scintillation light trigger. A linear fit of the 570keV Gamma ray line shows a lifetime of about 1.5ms. Electron drift velocity at 1kV/cm is about 2mm/s 976keV electron 554keV electron 570keV gamma ray 1064 keV gamma ray Light in addition to charge correlation There is clear anti-correlation between ionization (charge) in addition to scintillation (light) in liquid xenon. Energy resolution can be improved by combining charge in addition to light signals. 570keV Gamma Rays Light collection improvement with PTFE Adding PTFE wall in addition to PTFE piece on the bottom improved the light collection efficiency. The purity level of liquid xenon is not affected by PTFE. Light spectrum of Bi-207 at zero field was obtained with the PTFE structure. PTFE Light Spectrum, Bi-207 570keV 1064keV Operation of a dual phase xenon chamber Vg Bi-207 Vc Vg Bi-207 Vc LXe LXe GXe GXe 4kV/cm 4kV/cm 0.5kV/cm 0.5kV/cm Vg Bi-207 Vc LXe GXe 4kV/cm 0.5kV/cm Liquid level is below the Grid No ionization electron can escape from LXe to GXe at low extraction field (0.5kV/cm) => No proportional light is produced Proportional light Liquid level is above the Grid in addition to below the Anode Ionization electron can be extracted from LXe to GXe at high extraction field (4kV/cm) => proportional light is abundantly produced Liquid level is above the Anode Ionization electrons are collected by the Anode, no GXe => no proportional light is produced E E E Method of analysis of wave as long as ms Bi-207 energy spectrum, readout from proportional light signals Bi-207 energy spectrum, readout from charge signals directly. Proportional light Direct light Event wave as long as m shows both direct in addition to proportional light signals The area of the proportional light pulse is proportional to the ionization electrons. Spectrum of Bi-207 from the proportional light is compared with charge spectrum in a single phase operation (right) Lower energy threshold can be reached from proportional light Low energy x-ray from Bi-207 Electron emission in addition to proportional scintillation The negative ground state energy of quasi-free electron in liquid xenon requires an electric field to extract electron from LXe to GXe. For a full extraction of ionization electrons to gas phase, a field of 10kV/cm in the gas xenon is needed from our data. The proportional light yield is related to the field in the gas, the gas gap in addition to the gas pressure [Bolozdynya, NIM A 99] The proportional light yield has been measured as a function of reduced field (field/pressure)

Ratio between direct in addition to proportional light The ratio between proportional in addition to direct light as long as Bi-207 is measured to be about 500 at 1kV/cm drift field in addition to 4kV/cm in the gas phase. The gas pressure is around 2atm. With improved geometry in addition to control of the liquid level, we will improve light collection efficiency in addition to energy resolution, in addition to will lower the energy threshold. The ratio of proportional in addition to direct light will be measured as long as low energy electron recoils in addition to nuclear recoils with improved chamber. 570keV

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Biddell, Adam General Manager

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