1. Yong-Hamb Kim Low Temperature Detectors for Rare Event Search 2 nd Korea-China Joint Seminar on Dark Matter Search

2. 2 Outline Introduction –Basic idea of low temperature detectors –Sensor comparison (Thermistors, TES, MMC) Low temperature detectors in underground labs –Direct Search for WIMPs, –Search for ββ0ν Low temperature detectors at KRISS –X-ray sensors –Prospective R & D

3. 3 Solid State Detectors Measurement methods (Charge, Light, Temperature) Thermometer Charge collector Semiconductor Light detector Thermometer Scintillator “Low temperature favorable”

4. 4 Basic idea: Calorimetric detection Absorber Thermometer Thermal link Heat sink < 100 mK X-ray, e -, WIMP, etc. Choice of thermometers TES, MMC, Thermistor, STJ, KID etc.

5. 5 Why Low Temperature Detectors? High resolutionLow threshold 240g sapphire (CRESST-I)  580 eV at 10 mK, 99% efficiency Counting 1.5μm(0.8 eV) photons(NIST) Advantages of using cryogenic calorimeters Extreme sensitivity of energy resolution (ΔE/E < 1/1000) Ultra low energy threshold ( < 1 eV) Active for Charge, Light, Phonon chains

6. 6 What to measure? WIMP: CDMS, CRESST, EDELWEISS, etc. Nutrinoless double beta decay: COURICINO (COURE) Direct measument of neutrino mass: MARE Absolute measurement of radioactivity X-ray astronomy: Constellation-X, XEUS Energy Depressive x-ray spectroscopy γ-ray spectrometer Single photon counting: IR, visible, UV, etc. Bio-molecules: time-of-flight mass spectrometry

7. 7 Thermistors Neutron transmuted doped Ge thermistors Ion implantation doped Si thermistors Near metal-insulator transition R(T) : 1 M  100 M  Operated with conventional electronics Slow due to poor coupling between conduction electrons and lattice of the thermistor E dependent resistance Radioactive contamination ( 68 Ge, 3 H)

8. 8 Transition Edge Sensor (TES) Superconducting strip at T c (W, Ir/Au, Mo/Au, Mo/Cu,Al/Ag, etc.) R N : 10 m  1  Proximity effect : Tunable T c (20~200mK) Voltage Bias  negative feedback working point TES ΔIΔI I t ( 초전도상전이센서 )

9. 9 Metallic Magnetic Calorimeter (MMC) ( 자기양자센서 ) Magnetic material (Au:Er) in dc SQUID junctions Field coil Au:Er(10~1000ppm) weakly-interacting paramagnetic system metallic host: fast thermalization ( ~ 1  s) g = 6.8 50 G  Δε = 1.5  eV 1 keV  10 9 spin flips Si SQUID Loop Au:Er Absorber

10. 10 Different sensors Superconducting strip at T c (W, Ir/Au, Mo/Au, Mo/Cu) ΔE: 1.8 eV @ 6 keV TESMMC Magnetic material (Au:Er) in a SQUID loop ΔE: 2.7 eV @ 6 keV Thermistor Neutron Transmuted Doped Ge Ion Implantation Doped Si ΔE: 3.2 eV @ 6 keV Conventional electronics Absorber friendly Slow at low temp. Joule Heating Fast, Most sensitive MUX possible Narrow working temp. High-tech. fab. Fast, Wide working temp. Absorber friendly MUX being developed I of 167 Er

11. 11 Outline Introduction –Why? How? What? –Sensor comparison (Thermistors, TES, MMC) Low temperature detectors in underground labs –Direct Search for WIMPs, –Search for ββ0ν Low temperature detectors at KRISS –X-ray sensors –Prospective R & D

12. 12 Direct Search for WIMP using LTDs CDMS, EDELWEISS, CRESST High resolution, Low threshold Active background rejection

13. 13 Background rejection Nuclear recoil on electron recoil bkg Phonon Light Charge Different Ch/Ph or L/Ph ratio for electron recoils and nuclear recoils Event by event discrimination Energy in charge channel (keV ee ) Energy in phonon channel (kev) electron recoils (γ‘s) nuclear recoils (neutrons) Energy in light channel (keV ee ) Energy in phonon channel (kev) electron recoils (e - s, γ‘s) nuclear recoils (neutrons) CRESST CaWO 4

14. 14 Neutrinoless ββ decay with LTD Double Beta Decay with two neutrinos Double Beta Decay with no neutrino (Rare Spontaneous Nuclear Transition) Calorimetric Detection Source ≡ Detector (only neutrinos are allowed to escape from the bulk) e-e- e-e-

15. 15 COURICINO toward COURE COURE (741 kg TeO 2 ) plans to start data taking early 2010 COURICINO (40.7 kg of TeO 2 + NTD Ge) (2006) 130 Te : candidate for ββ-0ν natural abundance (34%) high transition energy (2.53 MeV) 5cm

16. 16 Outline Introduction –Why? How? What? –Sensor comparison (Thermistors, TES, MMC) Low temperature detectors in underground labs –Direct Search for WIMPs, –Search for ββ0ν Low temperature detectors at KRISS –X-ray sensors –Prospective R & D

17. 17 First signal at KRISS for rare events Signal size (a.u.) Counts cosmic ray 6 keV from 55 Fe 5×5×0.5 mm 3 Si with Ti/Au TES 2006/06 S.C. Kim Clear appearance of 6 keV x-rays Important demo. toward massive detectors WIMP, ν, 0νββ etc.

18. 18 Detector development at KRISS TES MMC field coil Au:Er Si SQUID loop 55 Fe spectrum Measured with MMC 2007/11/09, S.J. Lee Mn K a 2 Mn K a 1 18 eV FWHM

19. 19 R & D plan at KRISS Scintillating Detectors for 0νββ at Low temperatures CaMoO 4 Phonon sensor w. TES or MMC Additional light sensor Si or Ge Two detection channels phonon + light TES

20. 20 Comparison with COURE COUREprospect Crystal (abundance) 130 TeO 2 (34%) Ca 100 MoO 4 (9.6%) Q2530 keV3034 keV Phonon sensorNTD GeMMC or TES Debye Temp.260 K420 K B.G. RejectionTBA (none)Light ΔE/E, α( 3 MeV )1/1000 Mass741 kg LocationGran Sasso Start2010 ~ 1/3000 ?? Y2L ??

21. 21 LTD People at KRISS Staffs –Yong-Hamb Kim( 김용함 ) Kyoung-Bum lee( 이경범 ) Minkyu Lee( 이민규 ) Post docs and students –Young-Hwa Lee ( 이영화, post doc) –Yong-Dae Kwon ( 권용대, post master) –Sang-Jun Lee ( 이상준, PhD candidate, SNU) –Hwa-Yong Lee ( 이화용, PhD Candidate, Kongju U.) A few positions available for students and post-docs If interested, talk to us.

22. 22 Thank you ( 감사합니다 )

23. 23 Extra slides

24. 24 Phonon signals Phonon down conversion 1. Very high energy phonon (not stable) 2. 20 ~ 50 K phonon (stable) Anharmonic decay 3. Thermal phonon distribution Inelastic surface scattering Inelastic impurity scattering ~ ns ~ 10 μs Athermal signals: TES, MMC, NbSi Thermal signals: NTD, TES, MMC Size and shape of athermal signals also provide discrimination for surface events

25. 25 Cryogenic massive detectors EDELWEISS-IGe1 kgCh/PhNTD1996Modance EDELWEISS-IIGe2.1kg /10kgCh/PhNTD,NbSi2006Modance CDMS-IGe, Si1 kg, 250 gCh/PhNTD1996Stanford CDMS-IIGe, Si7 kg, 1.4 kgCh/PhTES2003Soudan SuperCDMSGe or Si25 kgCh/PhTES?Sudbury CRESST-IAl 2 O 3 1 kgTES1999Gran Sasso CRESST-IICaWO 4 0.6 kg/10 kgL/PhTES2003/06Gran Sasso CUORICINOTeO 2 40 kgNTD2003Gran Sasso CUORETeO 2 741 kgPh/surf. phNTD~2010Gran Sasso NameTargetTotal MassDiscrimThermometerStartLocation