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Status of EXO-200

Status of EXO-200. Carter Hall, University of Maryland DUSEL town meeting November 4, 2007. ITEP. ИТЭФ. A liquid xenon TPC as a  0  detector. Monolithic TPC design has optimal surface area to volume ratio Full three dimensional event reconstruction Fluid can be purified in situ

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Status of EXO-200

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  1. Status of EXO-200 Carter Hall, University of Maryland DUSEL town meeting November 4, 2007

  2. ITEP ИТЭФ

  3. A liquid xenon TPC as a 0 detector • Monolithic TPC design has optimal surface area to volume ratio • Full three dimensional event reconstruction • Fluid can be purified in situ • Noble gas isotope enrichment relatively easy and safe • No crystal growth • No long-lived xenon isotopes to activate

  4. The Centerpiece of EXO-200 200 kg of xenon enriched to 80% in 136Xe: the most isotope in possession by any 0 collaboration. 11 times larger than previous experiments.

  5. EXO-200: the first 200 kg bb0n experiment Copper liquid xenon vessel HFE-7000 cryofluid copper cryostat lead shielding 200 kg of Liquid Xenon to be contained in copper vessel, surrounded by 50 cm of ultra pure cryofluid inside a copper cryostat and shielded by 25 cm of lead.

  6. 3 2 1 EXO-200 is housed in a 100 class clean room Refrigerators hold the cryostat at liquid xenon temperature three of six modular clean rooms EXO clean rooms assembled at Stanford

  7. March 30, 2007: commissioning of cryogenics and fluid handling Refrigeration feedthrus Liquid xenon supply line HFE feedthru Liquid xenon return line Insulating vacuum pump-out 24 hour shifts for two months. First cooldown of 4 tons of HFE-7000. First xenon liquefaction for EXO-200. Dummy LXe vessel

  8. Summer 2007: cleanrooms being seperated at Stanford

  9. Summer 2007: moving the experiment underground

  10. Underground site is the WIPP facility in Carlsbad, NM A salt mine for storage of radioactive waste.... and for low radioactivity experiments!

  11. Fitting the cleanroom into the “waste hoist” – one ¼” to spare!

  12. EXO-200 underground at WIPP – September 2007 Cleanrooms expected to be fully operational in mid November. Plan to re-commission cryogenics in February.

  13. Thin (1.5 mm) copper liquid xenon vessel minimizes radioactivity, but it can’t withstand a large pressure differential. Inner cryostat door Liquid xenon inside HFE outside Xenon pressure and HFE pressure must be controlled to maintain no more than a 5 psi pressure difference across the xenon vessel. copper liquid xenon vessel

  14. Low Background Liquid Xenon Vessel Under Construction Each part made from ultra-pure copper Finished part Vessel made by e-beam welding

  15. The EXO-200 detector: a dual TPC charge drift direction cathode crossed wire planes and avalanche photodiodes field shaping rings

  16. acrylic supports ~40 cm LAAPD plane (copper) and x-y wires (photo-etched phosphor bronze) Central HV plane (photo-etched phosphor bronze) teflon light reflectors field shaping rings (copper) flex cables on back of APD plane (copper on kapton, no glue) x-y crossed wires, 60o

  17. Crossed wire planes and APD array measure event energy and position y-position given by induction signal on shielding grid. x-position and energy given by charge collection grid. APD array observes prompt scintillation to measure drift time.

  18. Liquid xenon data show an anti-correlation between ionization and scintillation 1 kV/cm Bi-207 source ~570 keV Energy resolution: 3.0% @ 570 keVor 1.4 % @ Q(bb) Factor of two better than most recent Xe experiment

  19. TPC wire grids produced by photoetching Charge collection with photoetched wire grids Wires connected in gangs-of-three to reduce channel count

  20. Scintillation detected by Avalanche Photodiodes Gang-of-seven APDs EXO-200 will have 259 APDs in each half of the detector Triply redundant electrical connections made by photoetched “spider” Copper APD holder

  21. Case Mass (ton) Eff. (%) Run Time (yr) σE/E @ 2.5MeV (%) Radioactive Background (events) T1/20ν (yr, 90%CL) Majorana mass (meV) QRPA1 NSM2 EXO-200 0.2 70 2 1.6* 40 6.4*1025 133 186 Sensitivity of EXO-200 • Improves on previous 136Xe experiments by one order-of-magnitude, • and competitive with the best 0 experiments in the world. • HM and IGEX (76Ge): ‹mbb› < 340 meV1 • EXO-200 will also make the first observation of bb2n in Xe-136. 1) Rodin, et. al., Nucl. Phys. A 793 (2007) 213-215 2) Caurier, et. al., arXiv:0709.2137v1

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