1. W. RauSNOLAB workshop 2009 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 1

2. W. RauSNOLAB workshop 2009 2 SuperCDMS Collaboration Caltech Z. Ahmed, J. Filippini, S. R. Golwala, D. Moore, R. W. Ogburn FermilabD. A. Bauer, F. DeJongh J. Hall, L. Hsu, D. Holmgren, E. Ramberg, J. Yoo MITE. Figueroa-Feliciano, S. Hertel, S. Leman, K. McCarthy, P. Wikus NISTK. Irwin Queen’s UniversityN. Fatemighomi, J. Fox, S. Liu, W. Rau, Santa Clara UniversityB. A. Young SLACE. do Couto e Silva, G. Godfrey Stanford UniversityP.L. Brink, B. Cabrera, M. Pyle, S. Yellin Southern Methodist UJ. Cooley Syracuse UniversityR.W. Schnee, M. Kos, J. M. Kiveni Texas A&MR. Mahapatra, M. Platt, M. VanDyke, J. Erickson UC BerkeleyM. Daal, N. Mirabolfathi, B. Sadoulet, D. Seitz, B. Serfass, K. Sundqvist UC Santa BarbaraR. Bunker, D. O. Caldwell, H. Nelson, J. Sanders U of Colorado at DenverM. E. Huber U of FloridaT. Saab, D. Balakishiyeva U of MinnesotaP. Cushman, M. Fritts, V. Mandic, X. Qiu, O. Kamaev, A. Reisetter U of ZürichS. Arrenberg, T. Bruch, L. Baudis, M. Tarka P. Di Stefano

3. W. RauSNOLAB workshop 2009 CDMS Technology Thermal coupling Thermal bath Phonon sensor Target + + + + - -- - + + + + - - - - - - - + + + e n Recoil energy [keV] Ionization signal [keV eeq] Nuclear recoils from neutrons Nuclear recoils from neutrons Electron recoils from β’s and γ’s Electron recoils from β’s and γ’s 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) 3 Operation Principle

4. W. RauSNOLAB workshop 2009 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 4

5. W. RauSNOLAB workshop 2009 CDMS Technology Ionisation/Recoil Energie Recoil Energie [keV] + + + + – – – – E + + + + – – – – + Surface Effect  -Band  -Band n-Band  ’s neutrons  ’s 5 Surface events

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

7. W. RauSNOLAB workshop 2009 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! 7

8. W. RauSNOLAB workshop 2009 Analysis and Results CDMS, Ge CDMS, Si EDELWEISS XENON 10 CDMS, Ge Combined Soudan Data CRESST 8 WIMP Limits

9. W. RauSNOLAB workshop 2009 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) 9

10. W. RauSNOLAB workshop 2009 Analysis and Results Example of Improvements (calibration data) Tighter NR yield band Fewer outliers in timing distribution OldNew 10

11. W. RauSNOLAB workshop 2009 SuperCDMS Larger detectors (250 g  630 g) Improved sensor design Tower  SuperTower More active detectors per tower: 4 out of 6  5 out of 7 (~ 1 kg  3 kg) 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 11

12. W. RauSNOLAB workshop 2009 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 detectors Difficult to estimate due to neutron background at testing facility 12

13. W. RauSNOLAB workshop 2009 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 13

14. W. RauSNOLAB workshop 2009 Shileding [mwe] log (Muon flux [m -2 s -1 ]) 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 SuperCDMS 14 SuperCDMS Sensitivity

15. W. RauSNOLAB workshop 2009 Detector R&D Interleaved electrodes: Electric field calculation Electrode/sensor layout Individual TES Phonon sensors on top and bottom i Z I Pi Z I P 15

16. W. RauSNOLAB workshop 2009 Detector R&D First iZIP data Excellent basic performance: Phonon energy resolution: << 1 keV Yield based discrimination: 1/3000 (considerably better than present detectors) Charge based discrimination: 1/1000 Additional discrimination from phonon signal timing and energy distribution between top and bottom Discrimination study limited by neutron background in (surface) lab. 16 Surface charge signal Bulk charge signal Recoil energy [keV] Ionization yield

17. W. RauSNOLAB workshop 2009 Underground TF Therefore we would like to investigating the option of setting up an Underground detector Testing Facility at SNOLAB 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 17 Mostly neutron background Motivation Recoil energy [keV] Ionization yield

18. W. RauSNOLAB workshop 2009 Underground TF 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 18 What would we need? Poly Lid Cryostat Water shield Crane

19. W. RauSNOLAB workshop 2009 Underground TF 19 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. W. RauSNOLAB workshop 2009 Roadmap Short Term: SuperCDMS @ Soudan -1 SuperTower operational -2 nd 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) 20

21. W. RauSNOLAB workshop 2009 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 kg Delayed by funding agencies (funding anticipated for FY 2011) R&D towards ton scale Ge DM experiment 21