09/04/2006NDM061 CANDLES for the study of 48 Ca double beta decay OGAWA Izumi ( 小川 泉 ) Osaka Univ. ( 大阪大学 )

09/04/2006 NDM062 Double beta decay of 48 Ca Largest Q value (4.27 MeV) next largest; 150 Nd (3.3 MeV) large phase space factor almost background free (  : 2.6 MeV,  : 3.3 MeV) Low Natural abundance → 0.187% large detector enrichment Next generation detector M det 2 if background free M det 4 if background limited

09/04/2006 NDM063 CANDLES CAlcium fluoride for studies of Neutrino and Dark matters by Low Energy Spectrometer undoped CaF 2 (CaF 2 (pure)) 48 Ca ( Q  =4.27 MeV ) 300 kg 6 t 100 t Liquid Scintillator (LS) 4  active shield Passive shield wavelength shifter for CaF 2 Photomultiplier large photo-caoverage

09/04/2006 NDM064 CANDLES I - POP (Proof of Principle) Detector CaF 2 (pure) crystal in liquid scintillator (with w.l. shifter) viewed by 4 PMTs (5 inch) LS : mineral oil + DPO (3 g/l) + Bis-MSB (0.3 g/l) 4  active shield

09/04/2006 NDM065 Performance Test (4  active shield) events from LS events from CaF 2 Clear separation between CaF 2 and LS 2 ADCs with different gate width 40 K

09/04/2006 NDM066 CaF 2 scintillator Internal Background (BG) at Q  High energy tail of 2  events  Good energy resolution Radioactive contaminations (U, Th-chain)  High purity crystal  Event selection using pulse shape information

09/04/2006 NDM067 Energy resolution Resolution Scintillation photons from CaF 2 (pure) <1/2 of CaF 2 (Eu) peak emission at U.V. (285 nm) Increase # of photo-electrons Wavelength shifter UV visible light CaF 2 (Eu) : from BICRON catalogue CaF 2 (pure) : measured value

09/04/2006 NDM068 Energy resolution Side View 9.14%(FWHM) Energy (keV) Counts Energy (keV) 60 Co (1333 keV) 5.91%(FWHM) 137 Cs (662 keV) CaF 2 (pure) wavelength shifter Standard  Source CANDLES I with 10 cm 3 CaF 2 (pure) Energy Resolution: 9.1 %(FWHM) at 662keV 3.4 % (FWHM) at 4.27MeV Req. for CANDLES III ; 4.0 %

09/04/2006 NDM069 Radioactive BG inside CaF 2 Natural Radioactive BGs ~ Q  Maximum energy   ~ 2.6 MeV,  ~3.3 MeV,  (max)~2.7 MeVe.e. (quench; f   ~ 0.3 ) Successive decays of  in decay chain  ~1  sec decay time CaF 2 E max =5.8MeV(U) 5.3MeV(Th)  Pulse shape

09/04/2006 NDM0610 Successive decays in U,Th-chain High Purity CaF 2 (pure) Crystal Rejection of double pulse Pulse Shape Discrimination between  +  and  events Space-Time Correlation (  and  +  ) Cut ( 208 Tl) 238 U 214 Bi 214 Po T 1/2 = 164  sec 232 Th 212 Bi 212 Po T 1/2 =  sec 64% U-Chain Q  = 8.95MeV Q  = 3.27MeV Q  = 2.25MeV 36% Q  = 6.09MeV 210 Pb Q  = 7.83MeV Q  = 4.99MeV 208 Pb stable    +     Th-Chain 208 Tl T 1/2 = 3.05min f   = 0.3

09/04/2006 NDM0611 Development of High Purity CaF 2 Crystals Radioactivities in CaF 2 (pure) Crystal (  -ray measurement) Radioactivities in CaF 2 Powder (HPGe measurement) U-chain( 214 Bi) ~35  Bq/kg … 1/30 of Previous Crystals (14±5  Bq/kg ;Best) Th-chain( 220 Rn) ~32  Bq/kg … 1/3 of Previous Crystals ( 6±1  Bq/kg ;Best) CaF 2 Powder Fused CaF 2 Raw Materials CaCO 3, HF CaF 2 Crystal Powder selection Crystal growing CaF 2 (Eu) in ELEGANT VI U-chain( 214 Bi) : 1100  Bq/kg Th-chain( 220 Rn) : 98  Bq/kg 93 crystals U and Th (ICP-MS)

09/04/2006 NDM0612 Rejection of Double Pulse Prompt Delayed Typical Pulse Shape (500 MHz FADC) 810ns 8.8ns time(2 nsec) pulse height (ch) time(2 nsec) pulse height (ch) PMT LinFI/O PM AMP FADC ‘ Dirty ’ CaF 2 crystal recorded shape fitted shape

09/04/2006 NDM0613 Pulse Shape Discrimination Pulse Shape discrimination Shape Indicator (PRC 67(2003) ) Difference in decay shape between  and  rays  -event  event mean value: no energy dependence (>1 MeV) 11

09/04/2006 NDM0614 Liquid scintillator Active shield Veto against external background Transparent to scintillation photon  Pseudocumene (PC) in mineral oil Wavelength shifter for CaF 2 (pure) UV visible light  PPO, Bis-MSB in UV transparent mineral oil  PC absorbs UV light

09/04/2006 NDM0615 Two Phase System CaF 2 (Pure) Concept of Method Conversion Phase  large conversion eff.  good transparency for UV Veto Phase  large light output with aromatic solvent  good transparency for visible light CaF 2 Emission (~285nm) Conversion by WLS (350~400nm) PMT propagate

09/04/2006 NDM0616 Performance of two phase system Liquid Scintillator for Conversion Phase Liquid Scintillator for Veto Phase conversion phase only (5 cm thickness) Two Phase system 5 mm no reduction 137 Cs

09/04/2006 NDM0617 CANDLES III CANDLES III (U.G.) ‘ Sanchika ’ Kamioka CANDLES III University R&D

09/04/2006 NDM0618 CANDLES III(U.G.) CaF 2 (pure) 10 3 cm 3 × 96 crystals; 305 kg Liquid scintillator two phase system Purification system H 2 O Buffer passive shield PMTs 17 ” PMT (×14) : R ” PMT (×56) : R8055 mirror type reflector photon trans. simulation energy res. ~3.5 Q  Kamioka underground lab.

09/04/2006 NDM0619 CANDLES III (prototype) Constructed at Osaka Univ. (sea level) small version for R&D check the performance of CANDLES CaF 2 modules 10 3 cm 3 × 60 crystal; 191 kg with conversion phase Liquid scintillator  1000× h 1000 acrylic container H 2 O Buffer : passive shield   00× h 2600 PMTs 15 ” PMT (× 8) : R ” PMT (×32) : R8055

09/04/2006 NDM0620 CANDLES III (prototype)  2.8 m h  2.6 m

09/04/2006 NDM0621 PMTs Photomultiplier Tube (13inch) Inside view

09/04/2006 NDM0622 PMT accident water leakage 31 PMTs of 40 are damaged replaced by modified version

09/04/2006 NDM0623 CaF 2 module CaF 2 + conversion phase + acrylic case half filled filled Index (CaF 2 ) Index (Mineral Oil)

09/04/2006 NDM0624 LS tank 4 CaF 2 modules installed

09/04/2006 NDM0625 Present status CANDLES III (prototype) Permission of using LS (~0.7 m 3 ) at Osaka Univ.  Sep./1/2006 by a fire dep. 4 CaF 2 modules installed R&D using prototype detector will start soon. CANDLES III (U.G.) Kamioka (ICRR) construction will start in summer 2007

09/04/2006 NDM0626 Mile stone CANDLES I, II, POP CANDLES III (prototype) CaF 2 (10cm 3 ) 191 kg CANDLES III (U.G.) Kamioka underground lab. (summer 2007) CaF kg ~30  Bq/kg for ~0.5 eV CANDLES IV 15 cm 3 cube (600 crystals) 6.4 t; Kamioka ~3  Bq/kg for ~0.1 eV in 6 yrs CANDLES V 100 t; SNO, Kamland or ??? for ~30 meV in 7 yrs another option; enrichment