1. 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

2. 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

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

4. 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) : Large CMO with ISTC
5) : Discussion with F. Fanevich
=> CMO by Lviv and collaborative effort
6) : CMO R&D in low temp. started by SNU group
7) ……….

5. 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

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

7. # of Photoelectron/keV
& Absolute light yield

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

9. Number of photoelectron from 60keV g
# of photoelecton from Am-241
Crystals tested
PE/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

10. 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 =
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): ±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)

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

12. 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

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

14. 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

15. Attenuation Length = ~ 30 cm

16. 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

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

18. 3” PMT side with Cs-137

19. L1-CMO

20. L2-CMO

21. Resoultion & light output comparison with S1 and UK2,UK3

22. Checking energy resolution with CdWO4
Energy resolution of 9%

23. Cs137 source with CMOs and CdWo4

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

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

26. S1 with Gaussian+Exp
18% FWHM

27. Mean time distribution of CMOs

28. 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.

29. 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->?)

30. 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

31. Thank you

32. 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