Characterization of Large CaMoO4 crystals for 0n bb search Presented by H.J.Kim (KyungPook National U.) 2007/11/24 2nd Korea-China Joint workshop

Double beta work status Sn-124 excited state, Zn-64 study was published in Nuclear Physics A 2007. 0-n bb for Sn-124 with LSC physics draft is in progress (NIMA published in 2007) CaMoO4 study is on going : Mo-92: EC/b+ study in 4p CsI(tl) shielding +CaMoO4 background test (J.I.Lee’s talk) SrCl2 : EC/b+ study in 4p CsI(tl) (J.So) CeBr3 crystal development for EC/b+, b+b+, study (Gulrooh’s talk) Sn-112 resonant 0n ECEC study with HPGe

CaMoO4 Scintillation crystals 12.5 cm 2.2 cm Korea(2004) Ukraina(2006) Russia(2006) Russia(2007), ISTC Project

History CaMoO4 crystal R&D in very fast progress 1) 2002 : Idea and try to grow CMO in Korea 2) 2003 : Discussion with V.Kornokov => Send test CMO (better quality) 3) 2004 : CMO characterizations and Conference presentation Extended idea of XMoO4, low temp. CaMoO4 4) 2005-2007 : Large CMO with ISTC 5) 2006 : Discussion with F. Fanevich => CMO by Lviv and collaborative effort 6) 2007 : CMO R&D in low temp. started by SNU group 7) ……….

Crystal used for test Russia S1 22x22x30mm S0 10x10x10mm Large (L1) 12.5 cm 2.2 cm S1 22x22x30mm S0 10x10x10mm Large (L1) 22x22x125 XL1, 2 30x30x210 f38x20 mm Ukraine UK2 UK3

Clustering method with 400 Mhz FADC The same method with Darkmatter Search Total 42 ms window with 34 ms pulse window

# of Photoelectron/keV & Absolute light yield

# of PE with 60keV gamma CdWo4 :197+-19 S1 :28+-8 UK2 :37.5+-8

Number of photoelectron from 60keV g # of photoelecton from Am-241 Crystals tested 0.6-0.7PE/keV : Ukraine 0.4-6PE/keV : Russia 0.5PE/keV : Korea * The size of crystals are different 0.6 PE/keV => 6% FWHM at 3MeV (theoretical limit) 9

CaMoO4 small absolute light yield CsI(Tl) reference test Cs-137 source Gain:20 Shaping time:4us HV:1800V Peak:1597±34.4 Pedestal:33±10 Resolution(FWHM): 4.9% e-h pair = 37000. NP = 37000/0.8/0.9 = 51000 CaMoO4 S0 test Na-22 source Gain:100 peak time:12us HV:1800V Peak:520±116 e-h of CsI(Tl): 8.6±1% 4300±500ph/MeV Assume 15% QE,90% eff 0.6 ± 0.1 PE/keV Need more study * Tested with LLAPD (Details by M.J.Kim)

Attenuation Length& Relative light output with S1 & XL1, XL2

Large size CaMoO4 test - using two 3" PMT’s and attached at both end faces of CaMoO4 crystal. made small holes of few millimeter diameter at every 2cm distance in the teflon along the length wise direction of the crystal. 12.5 cm 2.2 cm PMT1 PMT2

Comparison between S1 and L1 CaMoO4 Light yield of Big CMO/ Small CMO is 90%

Energy spectrum of Am-241 Placed the Am-241 radioactive source at every 2cm mark Red= 2cm Green= 4cm Blue= 6cm Pink= 8cm Black= 10cm

Attenuation Length = ~ 30 cm

Larger (XL1, XL2) CaMoO4 test - XL1,XL2 crystals were used for test. - using one 3" PMT (green extended) and one 2" PMT (bi-alkali) of CaMoO4 crystal. made small holes of few millimeter diameter at every 3cm distance

a test with S1 & XL1, XL2 XL1 : ~70% of S1, XL2 : ~80% of S2

3” PMT side with Cs-137

L1-CMO

L2-CMO

Resoultion & light output comparison with S1 and UK2,UK3

Checking energy resolution with CdWO4 Energy resolution of 9%

Cs137 source with CMOs and CdWo4

Cs-137 with S1 and UK2, UK3 Relative light yield ; 1.2 : 1.9 : 2.0

Different fitting, different results The best way is subtract background from data and fold MC data with data with Gausian fit only

S1 with Gaussian+Exp 18% FWHM

Mean time distribution of CMOs

Summary Different size of CMO crystals from Russia (ISTC project) and Ukraine are being tested # of photoelectron/keV, absolute light yield and attenuation length are measured Relative light output and energy resolution were compared.

Work list before experiment Resolution and light yield issue ->Different crystal results need to be resolved Test with the same size of LU3 and XL1 Improve light output… ->Further study of LAAPD : LAAPD or PMT? -> How low temperature is necessary? -> Size of CMO optimization Internal Background issue -> measurement UK3 (results) XL (soon…) => Shielding optimization for VETO Enriched 100Mo, purification, growing issues Low temp Det., XMoo4 (X->?)

Backgrounds and signal for 20kg of CaMoO4 with 5 years data taking (GEANT4) Sensitivity 10kg (100Mo) 5% FWHM resolution 0.05 mBq/kg for 208Tl, 214Bi 5 years  7.1x1024 y (90% CL) ( 0.18~0.71 meV) Mo-100 2n Ca-48 2n Signal (m=0.4eV) Bi-214 Tl-208 10s significance Current best limit on 100Mo : 4.6x1023 by NEMO3 with 6.9kg 100Mo Claim by Klapdor-Kleingrothaus et al.  ~ 400 meV  Assuming optimistic theoretical value

Thank you

New Crystal for Am-241 Distance Mean of det00 (2” PMT) Mean of det01(3” PMT) 1 15390 10960 3 14880 10950 6 14740 10990 9 14630 10930 12 14390 10610 15 13880 11398 18 15120 9494 Old Crystal for Am-241 Distance Mean of det00(2” PMT) Mean of det01(3” PMT) 1 12810 9370 3 11280 9785 6 10910 9784 9 10890 9695 12 10530 9757 15 9663 10460 18 11790 8416