Natural CMO+HPGe experiment Sejong University Kang Woon Gu KIMS Collaboration

Motivation 1.HPGe detector at the Y2L(700m) has higher background than other hpge detector by a factor of ~5-10. 2.This seems to be due to detector itself. We need a new detector for ultra-low background measurement. 1400m 233m IRMM 50 m 0 m Depth IRMM operates an underground laboratory at the premises of the Belgian Nuclear Research Centre in Mol, 233 m below the ground Gransso Fig.1

New HPGe detector Setup Fig.3 Mass Diameter Height 2.8kg 79.9 mm 84.3 mm Fig.2 Ortec mass = 2.424kg Last year  replace an ortec hpge as a canberra hpge

B.G Rate with CANBERRA HPGe Detector acrylic box open in oder to LN2 re-fill using data analyze ■U238 BackGround Rn Gas effect ■Th232/K40 BackGround Consistent Fig.4 ■ In last year, we measured bg levels for the new Canberra hpge detector And this figure shows the measured results. ■ In the case of the U238 bg levels  were higher because of Radon Gas effect ■ But, in case of the Ra226 is lower than previous Ortec Ra226 bg level ■ In case of the Th232 and K40 bg level  were Consistent ■ In order to compare ortec bg levels, in the case of consistent dataanalyze

B.G Level with ORTEC and CANBERRA U238 B.G level inconsisten  Rn Gas effect Fig.4 Good News Ra226 Fig.5 Bi214 Ra226 Pb214 K40/Th232 Background Consistent Tl208 K40 Tl208 Bi214 K40 Fig.7 Fig.6 ■ In case of the Ra226 is lower than previous Ortec Ra226 bg level Good News ■The U238,Th232,K40 levels are, respectively, about 2 times and 5 times and about 8 times lower than previous Ortec bg level.(Fig.5,6,7) ■ In order to compare ortec bg levels, we was analyze using consistent bg level

HPGe B.G Energy Spectrum Fig.9 P1 1.86evt/bin Black Line : ORTEC 0.0119 Hz Red Line : Canberra0.0060 Hz P1 5.08evt/bin 50keV~350keV P2 Fig.8 620keV~1200keV Fig.10 0.219evt/bin P2 0.431evt/bin ■ In the case canberra spectra, the bg levels are lower than the previous ortec bg levels about two times.(Fig.8) ■ Also, in low energy region from 50keV to 350keV, the spectra show difference between the results from the two detectors about 4 times maybe because of difference in the detector qualities.(Fig.9) ■ We have interests mainly at this flat region from 620keV to 1200keV without bg peak. in the flat region, the spectra are about 2 times lower than the ortec background. Fig.10

Energy Resolution-DAQ Setup Shaping Time = 6us HPGe Pre-Amp Ge-E ch0 Data Acquisition ORTEC 671 Amplifier Ch1(1/3) FADC400 ch2 Preamp Signal ■ Energy Resolution of HPGe detectord □ We was replace an MCA card as a FADC-400MhZ □ We want to confirm good energy resolution of HPGe Detector using a 400MHz fast-ADC(FADC) and ORTEC-671 Amplifier ■ Experiment DAQ setup □ in the case of the ch0  from 0keV to 700keV □ and, in the case of ch1  from 700keV to 3000keV also, three times smalls than ch0 signal Sigma*constant=area charge ■ UNI-Output singal – 671 Spectroscopy Amplifier □ Front- and rear-panel BNC connectors provide positive, unipolar, shaped pulses with a linear output range of 0 to +10 V

MCA-Card and Gammavision

ORTEC 671Amplifier Module Front Panel Rear Panel Uni-Output signal (1/3 signal) 700keV~3000keV One input Two output PreAmp Input Signal Uni-Output signal (Normal Signal)

Signal Shape Ch0 – Amp671 Front Signal Ch1 – Amp671 Rear Signal Ch2 – Preamp Signal X-axis : Time [ns] Y-axis : Height [mV] Fig.11

Energy Resolution □ MCA card (G=20) ■ MCA card( G=10) Ba133 700keV ch0 ch1 Ba133 Cs137 Co60 □ MCA card (G=20) ■ MCA card( G=10) ● FADC module(G=10) Ba133 Fig.13 Fig.12 Cs137 Co60 Fig.14 Fig.15

2E.C/EC β+ : Hamamtsu 3inch PMT Q-Value : HPGe detector ECEC and EC/β+ of 92Mo 92Mo nucleus is double EC and beta plus EC isotope Fig.16 In the Case of ECEC,Q-value is 1.65MeV for Mo92 2E.C/EC β+ : Hamamtsu 3inch PMT Q-Value : HPGe detector (A, Z) + 2e- -> (A, Z-2 ) + 1650keV(Q-value) Abundance = 92Mo: 14.84% We will perform a 2beta decay experiment for the Mo92 using the new HPGe detector

DBD DAQ Setup Pre-Amp x100 in CaMoO4 crystal Signal FADC400 Data Acquisition ch3 ECEC HPGe Detector Q-Value ch0 Pre-Amp in F-Out Ch1(1/3) R-Out Amp ch2 This slide shows our DAQ setup for ECEC and EC b+ experiment using the HPGe detector and the CaMoO4 crystal

HPGe detector  Q-Value measured DBD Experiment Setup ECEC CaMoO4 Crystal HPGe Detector 25X25X60 [mm] Q-Value 25 X 25 X 215 [mm] HPGe detector  Q-Value measured 3inch PMT  2EC/ECb+

Hamamatsu New PMT ■ 2EC/EC b+ signal measured ■ The R11065 are 76mm(3”) diameter head-on PMT with extremely low radioactivity ■ photocathode area : Φ64mm ■ High QE and High cathode linearity Response Cathode Current Linearity

Plane & Summary ■ U238 bg levels inconsistent because Rn gas effect ■ but, the Th232 and K40 levels consistent ■ the bg levels of canberra hpge  lower than ortec bg (U238,Th232,K40) ■ We was measured for good energy resolution using 400Mh FADC and amp671 module ■ We will performed a double beta decay experiment using a CaMoO4 crystal and new HPGe detector

Backup Slide

U238 /Th232/ K40 Decay Chain Rn222 Up Rn222 Down Rn220 Down Rn220 Down In csae of U238  Ra228 and Pb214, Bi214 In case of Th232  Ac228 and Pb212, Bi212 , Tl208