Development of InP solid state detector and liquid scintillator
containing indium complexes for measurement of pp/7Be solar neutrinos
and Neutrinoless double beta decay
Y.Fukudaa M.Asakurad B.Enkhbata T.Izawad S.Moriyamab T.Nambac A.Obataa H.Sekiyab K.Watanabeab ICRR, University of Tokyo

c ICEPP, University of Tokyo d Solid state division, Hamamatsu Photonics K.K.

1. Introduction

4. Liquid scintillator containing
metal complexes◆ Purpose : Measurement of precise mixing angle θ12・ 96%C.L. allowed region obtained by global fit
LMA solution (blue) : Cl + Ga + SK (D/N spectrum)
KamLAND (green) → confirm ∆m12227°< θ 12<37°・ mixing angle θ12 is not fixed compared with θ23 (obtained by Atm. ν)・ survival probability would increase at 5MeV or less in case of LMA
solution, and the shape depends on the value of θ12.
pp/7Be solar neutrino spectrum could obtain precise θ 12
● on-going solar 7Be experiment◆ Development of liquid scintillator using metal complexes● goal : solubility : 5 wt%, light yield : 60% of BC505, attenuation length : 2~3m
● 8-quinolinolate metal complex (InQ3 ZrQ4)
N・ AlQ3 has been established as organic Electro Luminescencematerial (maximum luminescence @ 530nm)
Mn+・ InQ3 (for solar ν) and ZrQ4 (for ββ-decay) should have same luminescenceOn● Solution of organic solvent
M = In, n = 3; M = Zr, n = 4● Synthesis efficiency

・ KamLAND (Liquid scintillator, electron elastic scattering [ES])・ Borexino (Liquid scintillator, ES)

InQ3
primary yield 100%sublimation 77%● future solar pp/7Be experiment
・ XMASS (LXe, ES, DARK MATTER)
・ LENS (Liquid scintillator loaded In/Ye, charged current [CC])・ othersZrQ4
primary yield 96%
sublimation 70%

Y.Suzuki@Neutrino2004◆ Contribution to determination of θ13◆ Technique of low energy solar neutrino detection● Advantage
・ large cross section (~640SNU)
・ direct counting for solar neutrinos
・ sensitive to low energy region (Eν ≧ 125keV)・ energy measurement (Ee = Eν － 125keV)・ triple fold coincidence to extract neutrino signal
from huge BG (e1 +γ2 + γ3 )● Disadvantage
・ natural β-decay of 115In115In + ν → 115Sn* + e (τ1/2 = 4.4 × 1014 yr , Ee≧498keV)
e1
115Sn*(4.76µs) → 115Sn + γ (115keV) + γ (497keV)・ possible BG due to correlated accidental
23coincidence by radiative Bremsstrahlung

R.S.Raghavan Phs.Rev.Lett.37(1976)259◆Indium Project on Neutrino Observation for Solar interior (IPNOS) experiment●Hybrid structure of InP and external scintillator

28.5cm
1.0cm

・InP multi-pixel detector (10mmX10mmX0.2mm cell)・external scintillator to detect γ1 and γ2●4tons of 115In detector for solar ν experiment
・ InP : 5.1tons (2.0X106 modules with ∆E/E~10% )・ high Z material for external scintillator
・ total size ~5m X ~5m X ~5m (depends on structure)

Excitation wave length (nm)

Excitation wave length (nm)● Quantum yieldemission wave length (nm)(Phys.Rev.Lett. 110(2008)141801)

emission wave length (nm)◆ Luminescence of 8-quinolinolate metal complex

・ Precise θ12 from solar neutrino experiment and KamLAND
experiment will contribute to determination of θ133.0cm

Solvent : Benzonitrile (PhCN: C6H5CN)
density : 1.0g/mL flash point : 75℃
Photon emission : 291nm@maximum
Solubility of InQ3 complex: 2wt%
Attenuation length : 66cm (@0.5wt%)

emission wave length (nm)a Miyagi University of Education

Excitation wave length (nm)● Light (energy) transfer to InQ3 / ZrQ4Quantum Yield :InQ3 5.0%
ZrQ4 1.1%

・ Number of expected events assuming no ν oscillation → 1885
・ Number of expected event assuming LMA solution with Ee≧100keV → 720

θ12 = 30°- 34°

Statistical and theoretical error in total → ~3.5 %◆ Performance of liquid scintillator

2. SI InP cell detector◆InP detector in vacuum dewar

Schematic view of InP detector
Size:
10mm×10mm×0.2mm
Electrode :・ Ohmic contact
・ Au vacuum evaporation
・Insulator (SiN) to avoid
leak current● Setup・ Hamamatsu H6410 2inch photomultiplier・ Fisherbrand 20mL Borosilicate Glass Scintilation Vials
・ Acrylic light guide・ LeCroy 1182 charge sensitive VME ADC
・ coincidence method was used for eliminating BG
・ Solution : PhCN with PPO 100mg and POPOP 10mg
● Response for γ−ray from radioactive source
1040keV :1925ch@0db(QE : 0.093)◆Response for γ−ray from radioactive source

Setup Clearpulse 5102 preamplifier
Clearpulse 4417 shaping amplifier
CAEN V419 peak sensing VME ADC

・ Measured clear photo- peak , but twopeak structure
・ Lower peak: induced charge(Led~200µm Lhe ~ 30µm)
Higher peak: e- full collection
・ Energy of electron-hole pair
production :3.5eV・ Energy resolution : 25%@122keV

1040keV :1525ch@0db(QE : 0.10)1040keV :2075ch@24db

20699ch@0db

15250ch@0db

33200ch@0db(QE : 0.25)

Quantum
Yield :
20699/132800=15.6%(5.0%)

Quantum
Yield :
15250/132800=11.5%(1.1%)132800ch@0db

Light Yield toBC505:
20699/208640=9.9%Light Yield toBC505:
15250/208640=7.3%

478keV:
1875ch@18db
expected :1907chInQ3 50mg

・ 30cm cubic chamber (like XMASS 100kg prototype detector)
・ InP multi-pixel detector inside of Liquid Xenon
・ Chamber includes ~10kg InP detector

PhCN coktailZrQ4 50mg

Photo luminescence caused by γ-ray was confirmed

3. IPNOS phase-I experiment◆ Detector

Light Yield
toBC505: 63%

5. Next step
◆ For IPNOS phase-I● Measurement of scintillation light from LXe◆ For liquid scintillator containing
metal complex● modify 8-quinolinolate ligand to add
substituent◆ Purpose・ demonstrate LowBG environment
・ long stable operation (1 ppν event will be expected for half year)◆ Requirements to detect γ3 (498keV)・ assuming surface coverage : 0.8
・ modify shape of electrode such as mesh structure
・ assuming 50% for naked area

Expected number of photon for γ3 is 8400,
which corresponds to 30keV electron equivalent

R8778 photomultiplier
Produced by Hamamatsu
Photonics (used for XMASS)・ direct measurement of LXe scintillation light・ construct small LXe chamber (volume : 0.15L)・ use R8778 PMT for coincidence method
・ finalize shape of electrode for InP detector
supported by Grant-in-Aid for Scientific
Research on Priority Areas 22011001● beta diketon complex
・ good solubility (over 10wt.%) has beenreported・ For ββ decay experiment, 4%@3MeV ofenergy resolution should be required.
supported by Grant-in-Aid forScientific Research (C) 22540303