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The EDELWEISS-II experiment Silvia SCORZA Université Claude Bernard- Institut de Physique nucléaire de Lyon CEA-Saclay DAPNIA/DRECAM (FRANCE), CNRS/CRTBT.

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Presentation on theme: "The EDELWEISS-II experiment Silvia SCORZA Université Claude Bernard- Institut de Physique nucléaire de Lyon CEA-Saclay DAPNIA/DRECAM (FRANCE), CNRS/CRTBT."— Presentation transcript:

1 The EDELWEISS-II experiment Silvia SCORZA Université Claude Bernard- Institut de Physique nucléaire de Lyon CEA-Saclay DAPNIA/DRECAM (FRANCE), CNRS/CRTBT Grenoble (FRANCE), CNRS/IN2P3/CSNSM Orsay (FRANCE), CNRS/IN2P3/IPN Lyon (FRANCE), CNRS/INSU/IAP Paris (FRANCE), CNRS-CEA/Laboratoire Souterrain de Modane (FRANCE), JINR Dubnia (RUSSIA), FZK/Universtat Karlsruhe (GERMANY)

2 Outline Limits of EDELWEISS-I EDELWEISS-II setup Current situation (3 detector types) Outlook

3 Direct Search Principle Detection of the energy deposited due to elastic scattering off target nuclei Event Rate : < 1 ev /kg/week Recoil Energy : 1 – 100 keV Low energy threshold Large detector mass Low background Radio – purity Active/passive shielding Deep underground sites

4 The EDELWEISS collaboration CEA Saclay (DAPNIA & DRECAM)Detectors, background, analysis, electronics, acquisition E. Armengaud, O. Bessida, M. Chapellier, G. Chardin, G. Gerbier, H. Deschamps, M. Fesquet, M. Gros, S. Hassani, S. Hervé, M. Karolak, X-F. Navick, P.Pari, B. Paul Post-doc: R. Lemrani, F. Schwamm Thesis : E. Grémion, A. Chantelauze (cotutelle FZK) CSNSM OrsayDetectors, cabling, cryogenics, analysis L. Berge, A. Broniatowski, D. Carré, S. Collin, L. Dumoulin, A. Juillard, F. Lalu, S. Marnieros Post-doc: Emilano OlivieriThesis : O. Crauste, X. Defay, Y. Dolgorouki, C. Nones IPN LyonElectronics, background, analysis, detectors F. Charlieux, M. De Jésus, P. Di Stefano, J. Gascon, M. Stern, V. Sanglard, L. Vagneron Thesis : S. Scorza, M.A.Verdier IAP ParisLow radioactivity, analysis C. Goldbach, G. Nollez CRTBT GrenobleCryogenics, electronics A. Benoit, M. Caussignac, H. Rodenas FZK/ Uni Karlsruhe (TH)Vetos, background N. Bechtold, J. Blümer, K. Eitel, V. KozlovThesis : A. Chantelauze (cotutelle CEA), H. Kluck JINR DubnaBackground E. Yakushev, A. SmolnikovThesis : A. Lubashevski, L. Perevozchikov 50 persons (30 FET), 11 PhD theses, 3 post-docs

5 Laboratoire Souterrain de Modane

6 Ge Heat-Ionization Detectors Simultaneous measurements: few V/cm with Al electrodes 17 mK with Ge/NTD sensor Different Ionization/Heat energy ratio for nuclear and electronic recoils (dominate bkg) Event by event background rejection => discrimination /n > 99.9% for E r >15keV

7 Edw-I limiting background PRD71, (2005) Background in the physics data taking Leakage from the to the recoil band Neutrons: - 1 n-n coincidence observed - Neutron shield not thick enough Surface electron recoils: - Bad charge collection (trapping and recombination) - Rate compatible with 210 Pb contamination: rate e- 5/kg.day E=5.3MeV Q= Pb 210 Pb 210 Po Best Sensitivity up to 2003, but…

8 EDW – II set-up radiopurity dedicated HPGe detectors for systematic checks of all materials clean room (class 100 around the cryostat, class for the full shielding) deradonized air (from NEMO-3) neutron shielding 20 cm Pb shielding 50 cm PE and better coverage active veto (>98% coverage) up to 110 detectors Ge/NTD + Ge/NbSi + new ID electrodes expected sensitivity: EDW-I × 100 -n pb (phase 100) = evts/kg/day (E r >10keV)

9 23*320g Ge/NTD : Developed by CEA Saclay and Canberra-Eurisys Amorphous Ge and Si sublayer: better charge collection for surface evts Optimized NTD size and homogeneous working T (16-18 mK) : goal keV resolution New holder and connectors (Teflon and copper only) LSM Ge-NTD detectors EDW-I rate: ~ 700 evts/kg/day for E>100keV After the most recent improvement EDW-II rate: ~ 300 evts/kg/day EDW-I rate on central electrode : evts/kg/day ( /m 2 /day) EDW-II rate ~ 3 evts/kg/day first low bg runs in 2006: old bg new bg

10 7*400g Ge/NbSi detectors : developed by CSNSM Orsay NbSi thin film thermometers for active surface evt rejection LSM Ge/NbSi detectors identification of surface events with Ge/NbSi detector data taken with 1 NbSi detector May&June 2007: 1.5kg.d (fiducial) Rejection works, resolutions needs tuning

11 ID detector Radius (cm) Z (cm) guard g: + 1V guard h: - 1V a electrodes: +2V b electrodes: +1V c electrodes:-2V d electrodes: -1V Electron trajectories hole trajectories a&c bulk event a&b near- surface event a,b&c event in low-field area 200g detector, concentric electrodes 2mm gaps, 200µm width trigger thresh. 24keV 241 Am source with 60keV ´s all events after cut b < 5keV (30% of evts. survive) recoil energy [keV] lab data

12 preliminary! status ID bolometer ~1.7 kg.d summary: first detector (200g) with interleaved electrodes in LSM performance as expected New 400g ID´s to be installed end of March

13 EDELWEISS-II next steps Goal 2x10 -8 pb (1200 kg.d no event) (~1 evt/kg/y) acquire physics data with 23 NTD build g NbSi Goal 2x pb (~10 evt/t/y) build 16 NbSi (same/tuned if needed) build 24 NTD with reduced contamination and/or with ID electrodes


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