1. Status of 100Mo based DBD experiment
J. H. So
Kyungpook National University
2nd International Workshop on Double Beta Decay search at KRISS

2. Theory issues 1/T0n 1/2 = G0n(E0,Z) |M0n|2 <mbb>2,
G0n(E0,Z) : phase space factor (~ Qbb5) : higher Q-value is better.
M0n-Nuclear Matrix Element, hard to calculate
Uncertain to factor 2-10, isotope dependent
Motivation to measure several isotopes
Experimental limits :
T0n 1/2 = (ln2/1.64) x 6 x1026   (a/A)  (M T/B R) 90% C.L.
B = background index in cts/(keV kg y)
R = FWHM energy resolution at Qbb in keV
M = mass of detector in kg, A = mass number of candidate material
e = detection efficiency at Qbb, a = bb isotope fraction (Enrichment),
t = measured time in years

3. Experimental methods for 0n DBD (e factor)
Source  Detector
(calorimetric technique) 
+ high energy resolution
+100% efficiency
- no event topology
+ event shape reconstruction
low energy resolution
low efficiency e-
source
detector
Source  Detector 
If you use the calorimetric technique :
Poor energy resolution
can mask the peak of 0n.
Signature: shape of the two electron
sum energy spectrum
two neutrino DBD
continuum with maximum at ~1/3 Q
R = 5%
sum electron energy / Q
neutrinoless DBD
peak enlarged only by the detector energy resolution

4. Energy resolution issue (R factor)
NIMA 584 (2008) 334
A.N. Annenkov et. al.
At least, 4-5% of energy resolution will promise to separate the 0n energy peak with 2n energy spectrum for 0n DBD search with 100Mo based crystal.

5. Why 40Ca100MoO4 scintillator? (a, B factor)
100Mo is one of promising candidate material for 0n DBD search. (Natural Abundance : 9.63%)
The enrichment of 100Mo is concerned with bb isotope fraction factor (a factor).
The natural Ca have been composed by 40Ca (N.A : 97 %) and 48Ca (N.A : %).
48Ca is also a candidate material of DBD. We need to use 48Ca distilled crystal to reduce
the background (B factor in previous formula).

6. BG Spectrum of SB29 for 80 days
Raw data
Anti-coincidence with front and back of 4p detector for internal BG

7. New 40C100MO crystal from Russia
SB35
SB28
CMO-3

8. Schematics CsI channel Preamp DAQ CsI channel
FADC
400MHz
CsI channel
10 times amplified for CMO
Preamp
DAQ
FADC
64MHz
CsI channel
10 times amplified for CsI
137Cs gamma ray source : 661-keV
Trigger conditions
- Threshold : 25 ADC (1V/1024 = 1ADC)
- Pulse width : 200 ns
- Photon number : 6

9. Light output / energy resolution of SB35
Resolution : 30% (FWHM)
Mean : 2.88 x 105
SB35
Resolution : 16% (FWHM)
Mean : 5.97 x 105
CMO_3
Resolution : 16% (FWHM)
Mean : 6.79 x 105

10. Upgrade of 4p CsI tagging detector
Previous setup
Future setup
CsI(Tl)
CsI(Tl)
CsI(Tl)
CsI(Tl)
CsI(Tl)
CsI(Tl)
CsI(Tl)
CsI(Tl)
14 CsI channel + 14 PMT
12 CsI channels (side) were shared
a PMT with neighbor channel.
14 CsI channel + 26 PMT
12 CsI channels (side) will be attached with 2 PMTs.
14 new PMTs (12 for upgrade and 2 extra) are prepared at KNU, and ready to test.

11. New DAQ machine DAQ machine for DBD at Y2L : kims10
Current DAQ machine has used for 4 years and data storage is not enough for our new experiment.
New machine has been prepared at KNU, we are installing the software for data taking.
SB35 is running with old kims10 machine.
After this running, we will replace the DAQ machine to new one.

12. Upgrade of external shielding
12 cm
CsI(Tl)
Lead 15 cm for external shield
Poly-ethylene 20 cm
40Ca100MoO4
N2 gas flowing
100 cm

13. Upgrade of external shielding
CsI(Tl)
Front side
23 cm
12 cm
Upper View
Lead 15 cm for external shield
N2 gas flowing
Poly-ethylene 20 cm
3 inch PMT : 13 cm + 7 cm
30 cm
3 inch PMT : 13 cm + 7 cm + CsI 6 cm
Extra space : 14 cm
100 cm
160 cm

14. 360 cm
90 cm
140 cm
4p Detector Rn
Detector
110 cm
HPGe
New 4p
Detector
100 cm
160 cm
Ukraine
CaMoO4
Setup
400 cm
220 cm
140 cm
80 cm

15. Summary and Future Plans
SB35 has better performance than the previous crystals. (SB28, SB29)
We took the background data for 3 weeks, it will be taken for 2 month with 4p CsI tagging detector.
#14 of PMTs have been prepared at KNU to upgrade the 4p CsI tagging detector.
The external shield will be required to upgrade for external background shielding. (lead and poly-ethylene)
The DAQ machine already have been prepared to replace the old machine.