Presentation is loading. Please wait.

Presentation is loading. Please wait.

The XENON Project A 1 tonne Liquid Xenon experiment for a sensitive Dark Matter Search Elena Aprile Columbia University.

Similar presentations


Presentation on theme: "The XENON Project A 1 tonne Liquid Xenon experiment for a sensitive Dark Matter Search Elena Aprile Columbia University."— Presentation transcript:

1 The XENON Project A 1 tonne Liquid Xenon experiment for a sensitive Dark Matter Search Elena Aprile Columbia University

2 Elena Aprile Dark Matter 2002 The XENON Collaboration Columbia University : E. Aprile (Principal Investigator) T. Baltz, A. Curioni (graduate student), K-L. Giboni, C. Hailey, L. Hui, M. Kobayashi and K. Ni (graduate student) Brown University : R. Gaitskell Princeton University : T.Shutt Rice University : U. Oberlack LLNL : W. Craig

3 Elena Aprile Dark Matter 2002 Current and Projected Limits of WIMP Searches Projection for CDMS Soudan (7kg Ge+Si) is ~1 event / kg / yr. Similar limits projected for competing experiments in Europe. It will take a substantial increase in target mass and superior background discrimination power to reach a sensitivity of ~1 event / 100kg / yr. For a Xe target with <10 keV recoil energy threshold this rate corresponds to a WIMP-nucleon  of ~ 10 -46 cm 2 A 1 tonne XENON experiment approaches this sensitivity, assuming 3.9x 10 -5 cts /kg /d /keV background rate, 99.5% discrimination and 10 keV recoil energy threshold.

4 Elena Aprile Dark Matter 2002 Liquid Xenon for a Dark Matter Detector Many favorable properties, from high Z (54) and density (3g/cc) for a compact instrument of flexible design, to high ionization (~60,000 e/ MeV) and scintillation yields if highly purified, to only stable isotopes...etc but a low energy threshold is essential for a sensitive WIMP detector. Expected rates of WIMP interactions in Xe and other targets as a function of recoil energy threshold for a 100 GeV WIMP with a  = 10 -9 pb (from R. Schnee).

5 Elena Aprile Dark Matter 2002 Ionization and Scintillation in Liquid Xenon I/S (electron) >> I/S (non relativistic particle)

6 Elena Aprile Dark Matter 2002 The XENON Experiment : Design Overview The XENON design is modular. An array of 10 independent 3D position sensitive LXeTPC modules, each with a 100 kg active Xe mass, is used to make the 1-tonne scale experiment. The TPC fiducial LXe volume is self- shielded by a few cm thick layer of additional LXe. The active scintillator shield is very effective for charged and neutral background rejection. One common vessel of ~ 60 cm diameter and 60 cm height is used to house the TPC teflon and copper rings structure filled with the 100 kg Xe target and the ~50 kg Xe for shielding.

7 Elena Aprile Dark Matter 2002 The XENON TPC: Principle of Operation 30 cm drift gap to maximize active target  long electron lifetime in LXe demonstrated 5 kV/cm drift field to detect small charge from nuclear recoils  internal HV multiplier (Cockroft Walton type) Electrons extraction into gas phase to detect charge via proportional scintillation (~1000 UV  /e/cm)  demonstrated Internal CsI photocathode with QE~31% (Aprile et al. NIMA 338,1994) to enhance direct light signal and thus lower threshold  demonstrated PMTs readout inside the TPC for direct and secondary light  need PMTs with low activity from U/Th/K

8 Elena Aprile Dark Matter 2002 The XENON TPC Signals: Nuclear Recoil Discrimination Redundant information from charge (secondaryl light) signal (S2) and primary scintillation light (S1) signal from PMTs and CsI photocathode Background ( ,e,  produce electron recoils with S2/S1 >>0 WIMPs (and neutrons) produce nuclear recoils with S2/S1~0 Depth of interaction Z from timing and XY from c.o.g of PMT signals. 3D event localization for effective background rejection via fiducial volume cuts

9 Elena Aprile Dark Matter 2002 The Columbia LXeTPC for Gamma-Ray Astrophysics 30 kg active Xe mass 20 x 20 cm 2 active area 8 cm drift gap with 4 kV/cm Charge and Light readout for calorimetry and 3D imaging 1 st LXeTPC demonstration in near space

10 Elena Aprile Dark Matter 2002 Compton Imaging of MeV  ray Sources with a LXeTPC

11 Elena Aprile Dark Matter 2002 Background Considerations for XENON  and  induced background 85 Kr (  1/2 =10.7y): 85 Kr/Kr  2 x 10 -11 in air giving ~1Bq/m 3 Standard Xe gas contains ~ 10ppm of Kr  10 Hz from 85 Kr decays in 1 liter of LXe. Allowing <1 85 Kr decay/day i n XENON energy band  <1 ppb level of Kr in Xe 136 Xe 2  decay (  1/2 =8 x 10 21 y): with Q= 2.48 MeV expected rate in XENON is 1 x 10 -6 cts/kg/d/keV before any rejection Neutron induced background Muon induced neutrons: spallation of 136 Xe and 134 Xe  take 10 mb and Homestake 4.4 kmwe  estimate 6 x 10 -5 cts/kg/d before any rejection  reduce by muon veto with 99% efficiency ( ,n) neutrons from rock:  1000/n/m 2 /d from ( ,n) reactions from U/Th of rock  appropriate shield reduces this background to  1 x 10 -6 cts/kg/d/keV Neutrons from U/Th of detector materials: within shield, neutrons from U/Th of detector components and vessel give  5 x 10 -5 cts/kg/d/keV  lower it by x10 with materials selection

12 Elena Aprile Dark Matter 2002 Background Considerations for XENON  -rays from U/Th/K contamination in PMTs and detector components dominate the background rate. For the PMTs contribution we have assumed a low activity version of the Hamamatsu R6041 (  100 cts/d ) consistent with recent measurements in Japan with a Hamamatsu R7281Q developed for the XMASS group (Moriyama et al., Xenon01 Workshop). Numbers are based on Homestake location and reflect 99.5% background rejection but no reduction due to 3D imaging and active LXe shield.

13 Elena Aprile Dark Matter 2002 Charge readout with GEMs: a promising alternative High gain in pure Xe with 3GEMs demonstrated Coating of GEMs with CsI 2D readout for mm resolution See Bondar et al.,Vienna01

14 Elena Aprile Dark Matter 2002 Proposed Strategy for XENON 10 kg prototype with all design parameters of 100 kg module. Demonstrate electron drift over 30 cm and charge/light readout under high field operation. Test with electron/nuclear recoils. Study Kr removal techniques (distillation, cryopumping). Develop and test low activity PMTs (Hamamatsu metal channel and/or Burle MCP based). Test multi GEMs charge readout in LXe. Studies of low activity detector materials. Finalize the design of a 100 kg LXeTPC after 2yrs of R&D. Construction phase of 1 st XENON module starts in 3 rd year. Enlarge collaboration and start underground operation by 2005.

15 Elena Aprile Dark Matter 2002 Summary Liquid Xenon is an excellent detector material well suited for the large target mass required for a sensitive Dark Matter experiment. The XENON experiment is proposed as an array of ten independent, self shielded, 3D position sensitive LXeTPCs each with 100 kg active mass. The detector design, largely based on established technology and >10 yrs experience with LXe detectors development at Columbia, maximizes the fiducial volume and the signal information useful to distinguish the rare WIMP events from the large background. With a total mass of 1-tonne, a nuclear recoil discrimination > 99.5% and a threshold of 10 keV, the projected sensitivity for XENON is  0.0001 events/kg/day in 3 yrs operation, covering most SUSY predictions.


Download ppt "The XENON Project A 1 tonne Liquid Xenon experiment for a sensitive Dark Matter Search Elena Aprile Columbia University."

Similar presentations


Ads by Google