Search for Dark Matter at CJPL with PANDAX Kirill Pushkin for the PANDAX Collaboration, 10 th...
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![Page 1: Search for Dark Matter at CJPL with PANDAX Kirill Pushkin for the PANDAX Collaboration, 10 th Rencontres du Vietnam, Very High Energy Phenomena in the.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d775503460f94a59fe0/html5/thumbnails/1.jpg)
Search for Dark Matter at CJPL with PANDAX
Kirill Pushkin for the PANDAX Collaboration,
10th Rencontres du Vietnam, Very High Energy Phenomena in the Universe,
August 3-9, 2014
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Contents
• Introduction• Experiment • Commissioning. Data taking.• Prospects and summary
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PANDAX: Particle and Astrophysical Xenon
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The PANDAX Collaboration
• Collaboration started in 2009 (includes ~40 people)
• 7 institutions
Shanghai Jiao Tong University,
Shandong University,
Shanghai Institute of Applied Physics, CAS,
Beijing University,
Yalong Hydropower Co., Ltd.
http://pandax.org
University of Michigan (USA)University of Maryland (USA)
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China JinPing Underground Laboratory (CJPL)
• ~2400 m overburden of rock• Deepest underground lab in operation
6720 m.w.e. ~57 muons/(year x m2)• Low radioactivity marble rock • Easy access – located in the middle of the 18 km tunnel
• μ – veto system unnecessary• compact shielding structure possible• easy access by road• future plans for CJPL II
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CJPL
SURFSURF
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Current layout of CJPL
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The PANDAX laboratoryXe detector
Ge counting station Storage bottles with Gas Xenon
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The PANDAX Detector
• Dual phase Xe detector• Probing WIMP-nucleon cross section• Designed for 1 T fiducial mass
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Stage I: 125 kg xenon target, 400 kg total massStage II: 500 kg xenon target, 1.3T total massStage III: 1.5 ton target, 3T total mass
III stages for PANDAX
Stage I
Stage II
Stage III
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External shielding
Passive shield Rn purge with N2 gas
• Reduces background from surrounding rocks and concrete• Passive shield allows accommodating a large, 1T, scale detector
• Continuous flush with boiled-off LN2
• Levels of Rn achieved < 1 Bq/m3 (limited by thesensitivity of the used Rn detector
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CryogenicsCooling power ~180 W (-96 degrees of Celsius)
LN cooling Heat exchangerPulse Tube Refrigerator
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Stage I TPC
Detector characteristics:
• TPC radius: 30 cm• Drift length: 15.4 cm
• Total Xenon mass: 400 kg• Sensitive target: Xe mass: 125 kg• Fiducial volume: Xe mass 37 kg
• Top PMTs array (1”, R8520): 143• Bottom PMTs array (3”, R11410): 37
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PANDAX- Stage I
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Background control: Detector materials counting
Use materials with low radioactivity: 238U, 232Th, 40K, 60Co
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PANDAX Stage I Progress
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PMT calibration with LEDs
LED calibrations:• 2 Teflon ball diffusers on top PMT array• LED and diffusers are coupled to optical fibers and feedthroughs• Gains balanced at ~2x106
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Calibration data systemWe can insert a gamma or neutron source into the tubing to calibrate the detector
3D position reconstruction important for further background reduction
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Xenon purity
• Electron lifetime ~262 us (drift time 20-80 us)
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S2 vs S1 light anticorrelation
40 keV (Xe-129)
80 keV (Xe-131)
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Gamma background rejection
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Radioactive background: Kr in Xe
• We employ a home made distillation column to remove Kr from gaseous Xe.
• We use an ultrasensitive Purity Analysis System based on RGA (MKS E-Vision 2).
• The amount of Kr-84 in our Xe after the distillation is of the order of ppt which can be subsequently recalculated in to the amount of Kr-85 in Xe.
Radioisotope Kr-85, T1/2=10.756 years. Beta maximum energy decay 687 keV
Kr-Xe distillation system
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Calibration measurements of Kr-84 in Xe gas
Measured by K. Pushkin and He Min Purity Analysis System
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Sensitivity projection (Stage I after 100 days of taking data)
Stay tuned for the Physics Results (17 days Dark Matter data paper will be released VERY SOON)
Leff cutoffbelow 3 keVLeff no cut offbelow 3 keV
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Upgrade: Stage II
Goals:• Upgrade in preparations. Stay tuned for more exciting news• Sensitivity reach 2x10-46 cm2 at 100 GeVwith 54000 kg-day.
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Future plans: CJPL-II
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Summary
• PANDAX has made a good progress in the past year. Currently, the experiment is taking data.
• Stay tuned for the coming 17 days Dark Matter data paper (expected to appear VERY SOON on arXiv).
• Currently, we are upgrading the detector, Stage I, to Stage II.
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Thank you for your attention!