AMoRE 0 experiment using low temperature 40 Ca 100 MoO 4 calorimeters

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1 AMoRE 0 experiment using low temperature 40 Ca 100 MoO 4 calorimeters Yong-Hamb Kim On behalf of AMoRE collaboration Institute for Basic Science (IBS) Korea Research Institute for Standards and Science (KRISS)

2 The AMoRE Project 2 AMORE: Love in Italian AMORE: A cosmetic company in Korea AMoRE: Advanced Mo-based Rare process Experiment to search for neutrinoless double decay of 100 Mo using cryogenic 40 Ca 100 MoO 4 detectors That s AMoRE for us! Ø4cmx4cm CaMoO 4 crystal

3 AMoRE collaboration (since 2009) 3 Russia Germany Ukraine 8 counties, 18 institutions, ~90 collaborators China Korea Pakistan Thailand Indonesia

4 Neutrinoless double beta decay (0νββ) 4 Double Beta Decay with two neutrinos Double Beta Decay with no neutrino requires massive Majorana ν! It may answer Mass of neutrinos ( T m ) 1 1/ 2 - Majorana ( ), or Dirac particles ( ) - Lepton number conservation?

5 Experimental Sensitivity of T 1/2 (0 ) 5 For sizeable background case: T 0 1/ 2 (exp) Detection Efficiency Isotopic Abundance (ln 2) N a a A Detector Mass MT b E Time Atomic mass Background level (count/kev kg year) Energy Resolution For zero background case: T 0 1/ 2 (exp) (ln 2) N a a MT A n CL

6 100 Mo is chosen for 0 experiment Mo High Q-value ( ) of (12) kev. High natural abundance of 9.6% Relatively short half life (0 ) expected from theoretical calculation m T 1/2 G0 M 0 me 2 Candidate Q (MeV) Abund. (%) 48 Ca Ge Se Mo Cd Sn Te Barea et al., Phy. Rev. Lett. 109, (2012) 136 Xe Nd

7 AMoRE detector technology 40 Ca 100 MoO 4 + MMC : Source = Detector 7 Photon(Light) sensor CaMoO 4 - Scintillating crystal - High Debye temperature: T D = 438 K, C ~ (T/T D ) 3-48 Ca, 100 Mo 0ν candidates - AMoRE uses 40 Ca 100 MoO 4 w. enriched 100 Mo and depleted 48 Ca Phonon(Heat) sensor MMC (Metallic Magnetic Calorimeter) - Magnetic temperature sensor (Au:Er) + SQUID - Sensitive low temperature detector with highest resolution - Wide operating temperatures - Relatively fast signals - Adjustable parameters in design and operation stages

8 Temperature dependent CaMoO 4 scintillation 8 From RT to 7 K, the light yield increases 6 times (V.B. Mikhailik et al., NIMA 583 (2007) 350) CaMoO4 absolute light ph/mev (H.J. Kim et al., IEEE TNS 57 (2010) 1475) Light yield at low temp. : ~ 30,000 ph/mev Largest light yield among Mo contained crystals.

9 40 Ca 100 MoO 4 crystals 9 Enrichment of 100 Mo (natural abundance : 9.6%) - Gas-centrifuge method - Enrichment of 100 Mo is higher than 96%. Depletion of 48 Ca (natural abundance : 0.157%) - Electromagnetic separation - Composition of 48 Ca is less than %.

10 Internal backgrounds of 40 Ca 100 MoO 4 crystals 10 4p CsI(Tl) active setup with Pb shielding at Y2L 4p gamma veto system a decay in 238 U 214 Bi (Q-value : 3.27-MeV) 214 Po (Q-value : 7.83-MeV) 210 Pb a a decay in 232 Th 220 Rn (Q-value : 6.41-MeV) 216 Po (Q-value : 6.91-MeV) 212 Pb Crystal S Po : 1.13-MeV 216 Po : 1.62-MeV, 363 events, 0.26mBq/kg 214 Po : 1.93-MeV, 2445 events, 1.74mBq/kg Crystal SB Po : 1.93-MeV, 63 events, 0.08mBq/kg 216 Po : 1.61-MeV, 57 events, 0.07mBq/kg 220 Rn : 1.44-MeV 214 Bi

11 Metallic Magnetic Calorimeter (MMC) 11 Magnetic material Au:Er(100~1000ppm) weakly-interacting paramagnetic system metallic host: fast thermalization ( ~ 1ms) g = mt Δε = 1.5 mev 1 kev 10 9 spin flips

12 MMC provides high resolution detection 12 1x1 mm 2 Au:Er layer designed for MeV signals Fabricated at KRISS Gold foil absorber Au:Er MMC chip Am241 full spectrum MMC with gold foil absorber with C ~ 0.3kg CaMoO kev FWHM <LTD16> G2.25 <2013 KRISS> 0.86 kev FWHM <LTD16> G2.25 S.R. Kim 0.4keV FWHM for 60keV 1.2keV FWHM Gaussian width for 5.5MeV a

13 <Heat flow optimization> Phonon sensor for AMoRE Phonon collector Patterned gold film MMC LTD15 13 Gold film Gold wires (thermal connection) rise-time: ~ 0.5ms We measure both thermal and athermal phonons.

14 Wafer holder (Cu, heat bath) Light (patchable) sensor with MMC Phonon collector (Gold films) SQUID sensor MMC chip 14 G4.35 H.J. Lee Light absorber (Ge wafer) Thermal connection Signal size ( 0 ) 6 x ~0.2 ms rise time at 30 mk Temperature independent rise-time! Time (ms)

15 Phonon + Photon Assembly 15 Phonon collector film on bottom surface 196 g 40 Ca 100 MoO 4 (doubly enriched crystal) Phonon collector film on bottom surface Light detector 2 inch Ge wafer + MMC

16 Particle discrimination 16 G3.34 G.B. Kim Particle discrimination by light heat ratio Phonon pulse shape discrimination (PSD)

17 Energy spectrum (above-ground) 17 G3.34 G.B. Kim Electron and alpha events can be efficiently identified. Better than 9 kev energy resolution was obtained at 10 mk temperature. Internal alpha background levels of each isotopes were calculated successfully.

18 Other detector R&Ds in AMoRE 18 Integrated light sensors Combined phonon and photon detector AuEr sensor with Au phonon collector Load ind uctor Photon ab sorber = Ge/Si isl and 3 Si/Ge bridge s define link to bath G4.33, C. Hassel

19 YangYang Underground Laboratory (Y2L) 19 AMoRE-pilot and AMoRE-phase1 will be run at Y2L. AMoRE-phase2 will be run at other place. (New underground lab.) NaI, Ge, 4 pi LTD lab separated two main labs Yangyang pumped storage Power Plant Minimum vertical depth : 700 m Access to the lab by car : around 2 km Experiments KIMS : dark matter search experiment AMoRE : 0νββ decay search experiment

20 20 AMoRE pilot: 1.5 kg 40 Ca 100 MoO 4 5 Crystals ( 40 Ca 100 MoO 4 ) with total mass ~1.5 kg SS g SB g S g NSB g SE#1 354 g

21 AMoRE pilot : 5 phonon + 6 photons 21 All are installed in a dilution refrigerator. with plastic scintillator muon veto

22 Now it is cold. 22 All of the shields are mounted. The dil. fridge reaches 8 mk with 250kg lead attached to MC We are improving noise figures now. - High friq.: reasonably low. - Low friq.: should be improved. with an external source at 20 mk

23 Schedule of the AMoRE project 23 Crystal: 40 Ca 100 MoO 4, doubly enriched scintillating crystals MMC technology for heat and light measurement Temperature: mk Zero background measurement in ROI Location: Y2L (till Phase I) and a new deeper place (after) Pilot Phase I Phase II Mass 1.5 kg ~5 kg ~200 kg Background (kev kg year) Sensitivity(T 1/2 ) (year) ~10 24 ~10 25 ~ Sensitivity(m ee ) (mev) < Location Y2L Y2L New Lab Schedule

24 AMoRE (CMO + MMC) development KRISS has been developing LTDs since 2005 Ø4cm x 4cm First CMO + MMC Large crystal Optimization cm 3 Presented at LTD13 LTD14 LTD15 Phonon + Photon at above-ground LTD16 AMoRE pilot Underground 5 crystals 40 Ca 100 MoO 4 Total mass 1.5 kg (Just started) Physics results Hopefully in LTD17

25 25 Postdoc positions are available in the AMoRE project.