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S u p e r C D M S Wolfgang Rau Queen’s University

S u p e r C D M S Wolfgang Rau Queen’s University. CDMS Technology Analysis and Results SuperCDMS Detector R&D Underground TF Roadmap. SuperCDMS Collaboration. Caltech Z. Ahmed, J. Filippini, S. R. Golwala , D. Moore, R. W. Ogburn

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S u p e r C D M S Wolfgang Rau Queen’s University

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  1. S u p e r C D M S Wolfgang Rau Queen’s University CDMS Technology Analysis and Results SuperCDMS Detector R&D Underground TF Roadmap

  2. SuperCDMS Collaboration Caltech Z. Ahmed, J. Filippini, S. R. Golwala, D. Moore, R. W. Ogburn Fermilab D. A. Bauer, F. DeJongh J. Hall, L. Hsu, D. Holmgren, E. Ramberg, J. Yoo MIT E. Figueroa-Feliciano, S. Hertel, S. Leman, K. McCarthy, P. Wikus NIST K. Irwin Queen’s University N. Fatemighomi, J. Fox, S. Liu, W. Rau, Santa Clara University B. A. Young SLAC E. do Couto e Silva, G. Godfrey Stanford University P.L. Brink, B. Cabrera, M. Pyle, S. Yellin Southern Methodist UJ. Cooley Syracuse UniversityR.W. Schnee, M. Kos, J. M. Kiveni Texas A&M R. Mahapatra, M. Platt, M. VanDyke, J. Erickson UC Berkeley M. Daal, N. Mirabolfathi, B. Sadoulet, D. Seitz, B. Serfass, K. Sundqvist UC Santa Barbara R. Bunker, D. O. Caldwell, H. Nelson, J. Sanders U of Colorado at Denver M. E. Huber U of Florida T. Saab, D. Balakishiyeva U of Minnesota P. Cushman, M. Fritts, V. Mandic, X. Qiu, O. Kamaev, A. Reisetter U of Zürich S. Arrenberg, T. Bruch, L. Baudis, M. Tarka P. Di Stefano

  3. CDMS Technology Thermal bath Thermal coupling Phonon sensor e n + + + - - Target - Ionization signal [keVeeq] - + + - - + + - + + + + Recoil energy [keV] - - - - Operation Principle • Measure energy deposit through thermal energy, requires low temperature • Electron recoil (ER) events produce more electron-hole pairs in semiconductor than nuclear recoils (NR) events do • Measure charge signal to discriminate between signal (NR) and background (ER) Electron recoils from β’s and γ’s Nuclear recoils from neutrons

  4. CDMS Technology • CDMS Detectors • Cryogenic ionization detectors, Ge (Si) •  = 7 cm, h = 1 cm, m = 250 g (100 g) • Thermal readout: superconducting phase transition sensor (TES) • Transition temperature: 50 – 100 mK • 4 sensors/detector, fast signal (< ms) • Charge readout: Al electrode, divided

  5. CDMS Technology g’s b’s g-Band + – – – – E + n-Band neutrons + – + + – + + + – – + Surface events Surface Effect b-Band Ionisation/Recoil Energie Recoil Energie [keV]

  6. CDMS Technology CDMS Setup 5 Towers: ~5 kg Ge, 1 kg Si “Tower” Stack of 6 detectors Operated in Soudan Lab (Minnesota) 2006 – 2009

  7. Analysis and Results • Published Data: • Data from Oct. 2006 – June 2007 • Raw exposure: ~ 400 kg days • Analysis threshold: 10 keV • Main analysis steps: • Cover signal region • Remove periods with bad detector performance • Determine position dependent calibration and timing performance • Remove multiple scatter & muon veto events • Remove surface events (timing) • 120 kg days after cuts • Calculate expected background • 0.6  0.5 events expected • Open the box • NO events observed!

  8. Analysis and Results CDMS, Si CDMS, Ge WIMP Limits EDELWEISS CRESST ZEPLIN I CDMS, Ge Combined Soudan Data XENON 10

  9. Analysis and Results • Presently under analysis • Data from July 2007 – fall 2008 • Increase of total exposure by a factor of ~3 • Improvements in data analysis: • Data quality cuts • Better algorithm to account for position dependence • Will need to tighten surface event cuts (timing) to keep expected background to < 1 event • Test new approaches for timing analysis • Timeline: announce results this fall • Expected improvement in sensitivity: factor 2-3 (similar to increase in exposure)

  10. Analysis and Results • Example of Improvements (calibration data) • Tighter NR yield band • Fewer outliers in timing distribution Old New

  11. SuperCDMS Larger detectors (250 g  630 g) Improved sensor design Short term goal: Build and install 5 SuperTowers (first installed/cold) Medium term goal: Further increase mass/module; build 100-200 kg experiment Long term: ~ 1 ton Tower  SuperTower More active detectors per tower: 4 out of 6  5 out of 7 (~ 1 kg  3 kg)

  12. SuperCDMS • Detector performance (test facility data) • Phonon energy resolution: similar to old detectors (in spite of 2.5 x mass) • Timing: faster due to larger Al coverage • Surface event discrimination: similar to old detectorsDifficult to estimate due to neutron background at testing facility

  13. SuperCDMS • First peek at SuperCDMS data • Determine alpha rate (indicator for expected surface beta background) • In fiducial volume: below target (0.4/detector/day) • Outside: rate scales as expected with area of side walls

  14. SuperCDMS log (Muon flux [m-2s-1]) Shileding [mwe] SuperCDMS Sensitivity • Need to reduce background! • Reduce surface contamination (Rn, volume/surface ratio) • Improve discrimination • Build new, cleaner setup • Reduce cosmic ray background by moving deeper • Move to SNOLAB

  15. Detector R&D Interleaved electrodes: +3 V 0 V iZIP Basic configuration Electric field calculation -3 V 0 V Individual TES Phonon sensors on top and Electrode/sensor layout bottom

  16. Detector R&D First iZIP data Bulk charge signal Ionization yield Surface charge signal Recoil energy [keV] • Charge based discrimination: 1/1000 • Additional discrimination from phononsignal timing and energy distribution between top and bottom • Excellent basic performance: • Phonon energy resolution: << 1 keV • Yield based discrimination: 1/3000(considerably better than present detectors) Discrimination study limited by neutron background in (surface) lab.

  17. Underground TF Motivation • Discrimination power required for 100 kg scale (or larger) experiments cannot be tested above ground (accidental neutron interaction rate too high) • Detector modules larger than present SuperCDMS detectors are desirable but cannot be tested above ground (pile-up) • Background from contamination of detectors cannot be measured above ground Ionization yield Mostly neutron background Recoil energy [keV] Therefore we would like to investigating the option of setting up an Underground detector Testing Facility at SNOLAB

  18. Underground TF What would we need? • Cryostat available at no (or low) cost (to be equipped with He re-liquefier) • Need to design shielding (water tank?) against environmental neutrons / gammas • Space: could be located in ladder lab without major impact on SuperCDMS setup Crane Poly Lid Water shield Cryostat

  19. Underground TF • Request from SNOLAB (first guess) • Installation • Support for lab interface (crane, electrical power, cooling water etc.) • Engineering support (SNOLAB specific design considerations) • Technical support during installation • Temporary space in surface building to test cryostat before moving UG • Transport of components to underground lab • Operation • Electrical power consumption: ~ 10 kW • Cooling water (~2 tons of cooling power) • Occasionally: liquid cryogenics (LN/LHe) • Some tech support First draft LoI available

  20. Roadmap • Short Term: SuperCDMS @ Soudan • 1 SuperTower operational • 2nd ST under preparation • ST 3-5: to be deployed during 2010 • Operation until summer 2012 • Medium Term: SuperCDMS @ SNOLAB • CFI proposal for infrastructure not funded • Will apply again next year • Funding anticipated in FY 2011 • Long Term: ton scale Ge dark matter experiment • R&D towards larger detector modules (up to 6” diameter) • Investigate feasibility of using lower grade Ge (to reduce cost per mass) • Work with Ge crystal producers to optimize production for our needs • Streamlining of detector production (improve production yield, reduce testing effort) • Investigate alternative sensor designs and readout schemes (multiplexing)

  21. Conclusions • CDMS continues to provide the most sensitive WIMP-nucleon cross section limits(WIMP masses above ~ 45 GeV and spin independent coherent interaction) • Factor 2-3 improvement expected very soon (data presently under analysis) • SuperCDMS started! First SuperTower is operational • Detector R&D: excellent performance for iZIP • Need Underground TF to demonstrate discrimination/performance of new detectors (iZIP, large substrates, …) for experiment with >100 kg target • Ask for comments from EAC wrt space allocation and support from SNOLAB (lab interface, engineering, technical support) for Underground TF • 5 ST @ Soudan to be deployed in 2010 • SuperCDMS @ SNOLAB: 100-200 kgDelayed by funding agencies (funding anticipated for FY 2011) • R&D towards ton scale Ge DM experiment

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