1. Min Kyu Lee ( 이민규 ) Kyoung Beom Lee ( 이경범 ) Yong-Hamb Kim ( 김용함 ) Low Temperature Detectors 2006 Workshop on the Underground Experiment at Yangyang TEXONO-KIMS collaboration meeting

2. LTD 2 Outline Basic idea –Calorimetric detection, Why? What? Sensors –NTD, TES, MQC Massive detectors –Search for WIMPs, 0ν-ββ, ν mass LTDs at KRISS –Future plan

3. LTD 3 Basic Idea: Calorimetric Detection x-ray, γ-ray, e -, WIMP, etc. Choice of thermometers NTD, TES, MQC etc.

4. LTD 4 Why Low Temp. Detectors? High resolution Low threshold NIST Al-Ag TES Si(Li) Low heat capacity dielectric ~ T 3 240g sapphire (CRESST-I) ~ 580 eV at 10 mK, 99% efficiency

5. LTD 5 What to measure? WIMP: CDMS, CRESST, EDELWEISS, etc. Nutrinoless double beta decay: COURICINO (COURE) Direct measument of neutrino mass: MANU, MARE X-ray astronomy: Constellation-X, XEUS, Astro-E2 Solar neutrino detector: HERON Energy Depressive x-ray spectroscopy Single photon counting: IR, visible, UV, etc. Bio-molecules: time-of-flight mass spectrometry x-ray absorption spectroscopy

6. LTD 6 NTD Sensor (Neutron Transmuted Doped Ge Thermistors) Near metal-insulator transition R(T) : 1 M  100 M  Operated with conventional electronics 4.5 eV at 6 keV (Alessandrello et. al. prl. 1999) Slow due to poor coupling between conduction electrons and lattice of the thermistor E dependent resistance Radioactive contamination ( 68 Ge, 3 H)

7. LTD 7 Transition Edge Sensor (TES) Superconducting strip at T c (W, Ir/Au, Mo/Au, Mo/Cu, Al/Ag, etc.) R N : 10 m  1  (2004) ΔE = 2.4 eV @ 6 keV

8. LTD 8 Magnetic Quantum Calorimeter (MQC) Magnetic material (Au:Er, Ag:Er, Bi 2 Te 3 :Er) in loop of a dc SQUID ΔE = 3.4 eV @ 6 keV 99 % quantum efficiency Brown-Heidelberg Au:Er (2003) KαKα KβKβ

9. LTD 9 Cryogenic massive detectors EDELWEISS-IGe1 kgCh/PhNTD1996Modance EDELWEISS-IIGe10 kgCh/PhNTD,NbSi2005Modance CDMS-IGe, Si1 kg, 250 gCh/PhNTD1996Stanford CDMS-IIGe, Si7 kg, 1.4 kgCh/PhTES2003Soudan CRESST-IAl 2 O 3 1 kgTES1999Gran Sasso CRESS-IICaWO 4 10 kgL/PhTES2003Gran Sasso CUORICINOTeO 2 40 kgNTD2003Gran Sasso CUORETeO 2 750 kgNTD~2007Gran Sasso NameTargetMassDiscrimThermometerStartLocation ROSEBUD, Tolyo-DM, ORPHEUS, MACHe3, etc.

10. LTD 10 Detection of signals for WIMPs Nuclear recoil on electron recoil bkg Phonon Light Charge Different Ch/Ph or L/Ph ratio for electron recoils and neutron 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

11. LTD 11 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 Thermal signals Size and shape of athermal signals also provide discrimination for surface events

12. LTD 12 Neutrinoless ββ decay U, Th contaminations on Cu give 50% bkg of ββ region (tested some ideas for surface event rejection) COURE (750 kg TeO 2 ) being built COURICINO: 40 kg of TeO 2 + NTD 130 Te : candidate for 0ν-ββ natural abundance (34%) high transition energy (2.53 MeV) Source ≡ Detector (neutrino is the only allowed to escape from the bulk)

13. LTD 13 Direct search for neutrino mass rel. Rate (a.u.) -3 -2 -1 0 E e -E 0 (eV) 1 0.8 0.6 0.4 0.2 0 m = 0 eV m = 1 eV E 0 = 2.46 keV Source ≡ Detector (neutrino is the only allowed to escape from the bulk) Published results: < 15 eV(90 C.L.) Milano MIBETA (AgReO4) < 26 eV(95 C.L.) Genova MANU (metallic Re) Future plan MARE phase I (MANU II, 2006~2009), goal < 2 eV TES or MQC phase II (2010~2015), goal < 0.2 eV, TES or MQC Theoretical β spectrum near endpoint

14. LTD 14 LTDs at KRISS MQC: We own the sensors (900 ppm Au:Er). TES: Ti/Au bilayer (DMRC & KRISS) Temperature (K) Resistance (Ω) Ti/Au (15/50 nm) Jan19/2006 Sensors

15. LTD 15 Absolute measurement of radioactivity (Future work at KRISS) No loss in source and detector Absolute measurement 55 Fe, 3 H, or other source in 4π geometry

16. LTD 16 High resolution EDS e-e- detector cryostat sample x-ray optics x-ray window (Future work at KRISS) Long term goal: resolution 3 eV at 6 keV count rate 10,000/s quantum efficiency 90% up to 6 keV Long term goal: resolution 3 eV at 6 keV count rate 10,000/s quantum efficiency 90% up to 6 keV

17. LTD 17 LTDs in the underground lab at Yangyang? Certainly possible ! We are open for new ideas and people !