Véronique SANGLARD Université de Lyon, UCBL1 CNRS/IN2P3/IPNLyon Status of EDELWEISS-II

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th1 Outline  EDELWEISS experiment  EDELWEISS-I limits  EDELWEISS-II setup  EDELWEISS-II preliminary results

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th2 The EDELWEISS collaboration  CEA Saclay  CSNSM Orsay  IPN Lyon  Institut Néel Grenoble  FZ/ Universität Karlsruhe  JINR Dubna *Expérience pour DEtecter Les WIMPs En SIte Souterrain (Underground experiment to detect WIMP)

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th3 LSM (Laboratoire Souterrain de Modane)

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th4 Heat and Ionization Ge detectors  Simultaneous measurement of  17 mK with Ge/NTD sensor  few V/cm with Al electrodes  Different charge/heat ratio for nuclear recoils (WIMP, neutrons) and electron recoils ( ,  )  E I /E R = 0.3 for nuclear recoils  E I /E R = 1 for electronic recoils  Event-by-event discrimination of electron recoils (main background) Neutrons 73 Ge(n,n',  ) Gammas Ionization guard Ionization center Fiducial volume(≈ 57%) Heat Thermometer (Ge NTD) Reference electrode Center electrode Guard Electrodes Ge crystal Center electrode Guard ring 7 cm m=320g Ionization threshold Amorphous (Ge or Si) ~ 60 nm

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th5 EDELWEISS-I (V.S. et al., PRD 71, (2005))  62 kg.d with 3 detectors  Best sensitivity up to 2003, but  Background  Neutrons : 1 n-n coincidence observed (2 singles expected by MC)  Surface electron recoils  Miscollected charge events at low energy  Leak of events down to the nuclear recoil band not visible in coincidence events  Rate compatible with 210 Pb contamination (  rate ~ 5 / kg.d)

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th6 EDELWEISS-II setup  Cryogenic installation (~ 20 mK)  Reversed geometry cryostat  Dilution refrigerator + pulse tube  Room for up to 120 detectors  Shielding  Clean room + deradonized air (15 mB/m 3 )  20 cm Pb  50 cm PE  Active  veto (> 98% coverage)  Facilities  Remotely controlled sources for calibrations and regenerations  Remote operations (cryogeny, acquisition, …)  Detector storage and repair within the clean room  9 cool-downs since January 2006

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th7 EDELWEISS-II setup  Cryogenic installation (~ 20 mK)  Reversed geometry cryostat  Dilution refrigerator + pulse tube  Room for up to 120 detectors  Shielding  Clean room + deradonized air (15 mB/m 3 )  20 cm Pb  50 cm PE  Active  veto (> 98% coverage)  Facilities  Remotely controlled sources for calibrations and regenerations  Remote operations (cryogeny, acquisition, …)  Detector storage and repair within the clean room  9 cool-downs since January 2006

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th8 EDELWEISS-II detectors  “standard” Ge/NTD bolometers (320 g) as for EDELWEISS-I  Ge/NbSi bolometers (400 g)  “interdigit” Ge/NTD bolometers ( g)

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th9 Results from “standard” NTD detectors  Commissioning background run (spring 2007) ~ 19 kg.d  8 lowest threshold detectors selected  Only « pure center » events selected for better Ei resolution  Reduction of factor 3 of  and  background Recoil energy threshold (20-35 keV) Ionization/Recoil Ratio

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th10 Results from “standard” NTD detectors Ionization/Recoil Ratio Recoil energy threshold (20-35 keV)  Commissioning background run (spring 2007) ~ 19 kg.d  8 lowest threshold detectors selected  Only « pure center » events selected for better Ei resolution  Reduction of factor 3 of  and  background

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th11 Results from “standard” NTD detectors  Significant reduction of the  background  Calibration with  source ( 210 Pb) to study the detector’s response to surface events  ~ 100 kg.d of fiducial exposure accumulated after quality cuts (analysis still underway)

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th12 Results from Ge/NbSi detectors  CSNSM since 2003  Goal : active identification of surface events using athermal phonon measurement with NbSi thin film thermometers  Each signal = thermal + athermal component  For surface events, athermal higher in corresponding thermometer  Thermal signals proportional to the deposited energy  Discrimination parameter = asymetry of athermal part of signals from the two surfaces  Surface rejection ok, some problems in 2007 with film contacts / leak currents  Resolutions hasn’t reached Ge/NTD performances

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th13 Results from Ge/NbSi detectors  CSNSM since 2003  Goal : active identification of surface events using athermal phonon measurement with NbSi thin film thermometers  Each signal = thermal + athermal component  For surface events, athermal higher in corresponding thermometer  Thermal signals proportional to the deposited energy  Discrimination parameter = asymetry of athermal part of signals from the two surfaces  Surface rejection ok, some problems in 2007 with film contacts / leak currents  Resolutions hasn’t reached Ge/NTD performances Data taken with 1 NbSi detector May & June 2007 ~ 1,5 kg.d fiducial

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th14 Results from Ge/Interdigit detector Radial coordinate (cm) Z (cm) guard electrode G : + 1V guard electrode H : - 1V A electrodes : + 2V B electrodes + 1V C electrodes : - 2V D electrodes : - 1V Electrons trajectories holes trajectories A & C Bulk event A, B & C Event in low-field area A & B Near surface event  Keep the standard phonon detector  Modify the E field near surfaces with interleaved electrodes (6 ionization channels)  Use B and D signals as vetos against surface events  From preliminary sea-level measurements  Surface event rejection > 95 %  Fiducial volume ~ 50 %

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th15 Results from Ge/Interdigit detector  Few kg.d of background LSM with a 200g detector  Performance as expected (resolutions, threshold, …)  Currently  3 new 400g detectors  Precise measurement of  rejection  A promising detector with a simple design  calibration Neutron calibration EDELWEISS-II ID-201 EDELWEISS-II ID-201

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th16 Results from Ge/Interdigit detector  Few kg.d of background LSM with a 200g detector  Performance as expected (resolutions, threshold, …)  Currently  3 new 400g detectors  Precise measurement of  rejection  A promising detector with a simple design E R threshold < 20 keV No event below Q=0.5 EDELWEISS-II ID-201 (4 kg.d)

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th17 Current run (May …)  Instrumented detectors:  23 “standard” Ge/NTD bolometers  5 “NbSi” bolometers  4 “Interdigit” bolometers ~ 10 kg of Ge

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th18 Conclusion  “standard” Ge/NTD detectors  Improved background understanding : significant reduction of ,  and  backgrounds  100 kg.d recorded and in analysis  Ge/NbSi detectors  Surface rejection ok  Resolution improvements needed  Ge/Interdigit detectors  December 2008 : 9 additional detectors  July 2009 : 120 kg.d fiducial exposure with threshold < 20 keV  Up to 35x320g Ge crystals available for reconfiguration as Ge/Interdigit

SANGLARD V., « Dark Energy and Dark Matter », Lyon, 2008 July 10th19 EDELWEISS prospects  1 st Goal :  4x10 -8 pb in 2010  Acquire physics data with 32 Ge/ID  2 nd Goal :  Few pb in 2012  ~ 70 detectors Ge/ID  EURECA (see H. Kraus’s talk next session)