Supported by Grant-in-Aid for Scientific Research (C) 24540295 andGrant-in-Aid for Scientific Research on Innovative Areas 24104501

Development of liquid scintillator
and its application to Neutrino
Physics
186th committee on radiation science and its application
FY2012 5th meeting
March 2nd , 2013
Yoshiyuki FUKUDA (Miyagi University of Education)

In the beginning of neutrino physics

Frederick Reines…with Clyde Cowan, another Los Alamos staff member. We initiallyconsidered the use of a nuclear bomb test as the source of neutrinos,
but soon decided that the reactor at Hanford, Washington, would bebetter.

In 1956, it was succeeded to detect ne using
liquid scintillator from commercial reactor.
March 2nd, 2013

186th committee radiation science andits application2

Detection method for anti-electron neutrino

nenp

2.2MeV g-ray
DT = ~ 200 msece+

No pre-activity

Very tiny post-activity with DT=~200msec.
186th committee(trig. eff.=~1%)
radiation science and3March 2nd, 2013its application

Elementary particle

電荷０-1-1/3+2/3
軽い

March 2nd, 2013

186th committee radiation science andits application
4重い
ニュートン１９９８年７月号

Neutrino oscillation
mass eigenstateandn2(mass=m2） n3(mass=m3）

mixture of mass eigenstate n2 and n3

Muon neutrino

Tau neutrino

Neutrino oscillation is easily explained byinterference 186thof wave.
committee radiation science andMarch 2nd, 2013its application
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If

and

are same mass, wavelength is same
波の伝播

時間

合成した波

（うなり）

6

March 2nd, 2013

186th committee
radiation science and its
application

ifandare not same, wavelength is different
波の伝播

時間(位置)

合成した波

（うなり）

7

March 2nd, 2013

186th committee
radiation science and its
applicationNeutrino oscillation experiments
If neutrinos have a finite mass, they will change flavor
state in the pass of flight.
P(na→nb) = sin22q sin2(1.27Dm2L/E)
cf. assuming E=1GeV L=250km

Dm2=0.001eV2 at maximum
 Appearance experiment

Searching for neutrinos which does not exist at source Disappearance experiment

Measurement of intensity of known flavor of neutrinos fromsource

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CHOOZ experimentsin22q13＜0.2 @ Dm213=2×10-3eV2
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KamLAND experiment

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186th committee radiation
science and its application

Kashiwazaki –kariwa
Nuclear power station

10

Allowed region of oscillation parameters
Consistent of resultsfrom solar neutrino
experiments
LamLAND

Solar neutrinos

March 2nd, 2013

Evidence of solar
neutrino oscillation

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Recent reactor experiments
P(ne→ne)=1-sin22q13sin2(Dm213L/4E)+O(10-3) (as Dm12~solarn )cf. E=4MeV and sin22q13=0.1

KamLAND
12

March 2nd, 2013186th committee
radiation science and itsapplication

Discovery of finite q13

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Neutrinoless double beta decay[T1/20n(0+ ->0+)]-1 =G0n(E0,Z)|M0n|2<mn>2
T1/2~a(Mt/DEB) a: abundance M: masst: meas.time DE: energy res. B: BG rate
Requirement : Low BG, Large target mass, High energy
resolution
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For future experiments

high energy
resolution
4%@2.5MeVF.Piquemal@n2012

http://kds.kek.jp/getFile.py/access?contribId=37&sessionId=16&resId=2&materialId=slides&confId=9151~tons of target will be needed for next generation detector
March 2nd, 2013

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Future experiments for Neutrinolessdouble beta decayExperimental requirement
for BG rate and DE

 To achivemn < 100meV high energy
resolution
4%@2.5MeV low background rate
0.01count kg-1 y-1
 ton scale of target

Liq. Scintillator is easy to scale up target volume
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Piquemal@n2012

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March 2nd, 2013

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K.Inoue@n2012

Pseudocumene
20%+Dodecane
80%+
PPO
0.15wt%March 2nd, 2013

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March 2nd, 2013

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Detector design for ZICOS experimentZirconium Complex in Organic liquid Scintillator(ZICOS) for double beta decay experiment

Assuming 10w.t.% solubility

3m

Zirconium loaded 100ton LS
March 2nd, 2013

10m

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Zirconium β-diketon complex
 Zirconium(IV)acetylacetonate(Zr(acac)4)

 Advantage
 good solubility (over10w.t.%) in Anisole(PhOMe) Stable and cheep Commercial product Disadvantage
 Low scintillation light

Molecular weight : 487.66
March 2nd, 2013yield

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What’s problem
 Absorption spectra ofIn(acac)3 (indiumacetyl acetone) wasoverlapped with theemission spectra fromAnisole （Chem. Phys.
Lett., 435(2007), 252)

Same overlap between the emission
and the absorption could be occurred
even if different metal (Zr) was used.
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Observed absorption spectra of Zr(acac)4
 Emission peak ofanisole was observed
around 295nm.
 Absorption peak ofZr(acac)4 was observed
around 270nm.
Scintillation light fromanisole (PhOMe) might beabsorbed by Zr(acac)4March 2nd, 2013

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Simple expectation for quenching Assuming to same cross section

for light
Light yield = L0 ×s1Nppo
s1Nppo + s2NZr
L0 : Light yield of anisole +PPO + POPOP
Nppo , NZr : Number ofmolecular for PPO and Zr(acac)4
s1,s2 : cross section of absorbance for
PPO and Zr(acac)4March 2nd, 2013

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Scintillation Light yield (60Co) withrespect to concentration of Zr(acac)4March 2nd, 2013

concentrationof Zr(acac)4ObservedchannelExpectedchannel

0 mg

3850

3850

50mg
(1.03X10-4)

3175

3138

100mg
(2.05X10-4)

2800

2651

200mg
(4.10X10-4)

2000

2018

300mg
(6.15X10-4)

1600

1613

500mg
(1.03X10-3)

900

1178

186th committee radiation science andits application

PPO 100mg : 4.52X10-4 mol
26

Improvement of scintillation light yield Move absorption peak

to shorter wavelength How to do it?

substituent groups
http://www.hi-ho.ne.jp/hosomi/sotsuron

Courtesy of Prof. Yoshiyuki Kowada(Hyogo University of Education)
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Absorbance peak for several
substituent groups
Measured absorbancepeaks for several
substituent groups

March 2nd, 2013



Expected absorbancepeak for several
substituent groups

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Zr b-diketon complex introducing
substituent groups (β-keto ester complex)
Zr(CH3COCHCOOCH(CH3))4 = Zr(iprac)4
mw : 711.92

March 2nd, 2013

Zr(CH3CCOCHCOO
CH3)4 = Zr(etac)4
mw : 665.81

186th committee radiation science andits application29

Zr β-keto ester complex
Zr(iprac)4+(iprac)1.5
state: powder

Zr(etac)4
state : dry solid

Synthesized by Prof. Takahiro Gunji (Tokyo University of Science)

Solubility > 10 w.t.% for anisoleMarch 2nd, 2013

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Absorbance spectra (Solvent effect)
Solution : Hexane

Solution : acetonitrile

solvent effectAbsorption peak moves to shorter wavelength,
however it depends on the polarity of solvent.
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Absorbance in liquid scintillator
Solution : Diethyl Ether

Solvent effect could
depend on the polarity(dielectric const.)
 Acetonitrile : 37.5

 Hexane : 1.89
 Anisole : 4.3

Need solution which hassame polarity as anisole Diethyl ether : 4.33

Still solvent effectremains around 270nm
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Light yield of Zr β-keto ester scintillator
Zr(iprac)5.5 in anisoleZr(etac)4 in anisole0%0%

1w.t.%

1w.t.%

5w.t.%

5w.t.%

Same quenching as Zr(acac)4 was observed
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Requirement of scintillator solvent
Low polarity (lowdielectric constant) No absorption ~270nm

Aromatic compounds
 luminescence >270nm

Keep high solubility >~10% Keep luminescence fromsolventPossible solvent:Toluene / Xylene
March 2nd, 2013

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A.McDonald @ n2012
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IPNOS phase-I experiment for low energy
solar n experiment
InP multi-pixel detector inside of
Liquid Xenon (LXe) with PMTs

30cm cubic chamber (like XMASS
100kg prototype) includes ~10kg
InP detector~103 modules will be neededin the final IPNOS (~10ton InP)

Need larger area InP detector
March 2nd, 2013

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Capture of low energy solar neutrinos by 115In
R.S.Raghavan Phs.Rev.Lett37(1976)259● Advantage
・ large cross section (~640SNU)
・ direct counting for solar neutrinos
・ sensitive to low energy region(En ≧ 125keV)・ energy measurement (Ee = En － 125keV)・ triple fold coincidence to extract neutrinosignal from huge BG (e1 +g2 + g3 )● Disadvantage
・ natural b-decay of 115In(t1/2 = 4.4 × 1014 yr , Ee≧498keV)・ possible BG due to correlatedcoincidence by radiative Bremsstrahlung

Goal
Nuclear Physics A 748 (2005) 333-347

ne115Sn*(4.76ms) → 115Sn +g1(115keV) + g 2(497keV)
115In +→ 115Sn* + e-

March 2nd, 2013

1.
2.
3.

Good energy resolution :10%(FWHM)
Fine segmentation (104-105)
High efficiency g detection

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LENS
R. Raghavan@Neutrino2010

38
March2nd, 2013

186th committee radiation science andits application

Development for new LS for IPNOS
phase-II (solar neutrino experiment) Liquid Scintillator

containing Inium βketo ester complex

 Advantages
 Cheep and stable 10ton In in 100ton LS Possible same design

as ZICOS Low energy solar n pp/7Be and CNO n
 Modulation using 7Be n

 Supernova n burst
 ne burst formNeutralization
March 2nd, 2013

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Cross section for 100MeV- 1GeV nn-nucleus cross sectionSensitive to neutralization burst

Rhy.Rev.C53(1996)1409

100ton of indium detects
20-100 ev
115In has ~10-39 cm 2 for 20-100Me

compared with snee~10-43 cm2
March 2nd, 2013

 Nuclear synthesis (r-process) n mass hierarchy

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Zirconium complex with luminescence Zr-ODZ complex

 Photo luminescencem.w. = 1040.18
Solvent : Acetonitrile
Concentration : 3.0×10-5 mol/L
March 2nd, 2013

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Emission and absorption spectrum ofZr(ODZ)4• Emission wavelength :430nm
emission

PMT sensitive• Absorption wavelength:
270nm and 320nm
absorption

March 2nd, 2013

different from excitation W.L.

• Solvent : PhCN(Benzonitrile)• Solubility : ~5w.t.%186th committee radiation science andits application

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Response for g-irradiation
Most of emission light fromPhCN was not used for theemission of Zr(ODZ)4.
 third excitation of ~340nm
from PPO was used for theemission of Zr(ODZ)4.
 Estimated Quantum yield
was obtained ~30% at firstexcitation of ~240nm.
Need another solvent
which has shorter emission
wavelength than PhCN.
March 2nd, 2013

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Summary Liquid scintillator is ordinal and popular technique toobserve neutrinos
 High solubility of Zirconium β-keto ester in Anisole(>~10w.t.%) was achieved.
 Confirmed absorption peak moves to shorter
wavelength (275nm → 245nm) by introducing ester
substituent groups.
 Observed scintillation light yield decreased inproportion to the concentration of Zr β-keto ester due
to solvent effect
Need low polarity solvent Indium β-keto ester complex will be developed forIPNOS phase-II in next fiscal year.
March 2nd, 2013

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BACKUP

March 2nd, 2013

186th committee radiation science andits application

45Tetrakis 8-quinolinolate Zr complex loaded
scintillator
Tetrakis (8-quinolinolate)
Zirconium complex (ZrQ4)

ZrQ4 50mg in PhCN-POPOP
Quantum
Yield=1.1%
obtained by
optical method

NMn+O-n

M = In, n = 3; M = Zr, n = 4

Light Yield toBC505:=7.3%

ZrQ4 m.w. = 689.07
March 2nd, 2013

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Scintillation light yield (137Cs) withrespect to concentration of Zr(acac)4March 2nd, 2013

concentrationof Zr(acac)4ObservedchannelExpectedchannel

0 mg

2450

245050mg

1800

1997

100mg

1400

1687

200mg

950

1284

300mg

650

1038

500mg

300

750

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Photo Luminescence and absorption of PPOPhoto luminescence Fluorescence device: HORIBA

FluoroMax-4
 Absorbance device : HITACHI
U-3000 Solvent : Benzonitrile (PhCN) Concentration : 1.0×10-5 mol/L 2,5-Diphenyloxazole
 Molecular mass : 221.26
 Max. emission wavelength :368.0nm Max. absorption wavelength :309.7nmMarch 2nd, 2013

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Photo Luminescence and absorption ofPOPOP

Photo luminescence Fluorescence device: HORIBA

FluoroMax-4
 Absorbance device : HITACHI
U-3000 Solvent : Benzonitrile (PhCN) Concentration : 1.0×10-5 mol/L 1,4-Bis(5-phenyloxazol-2-yl)benzene
 Molecular mass : 364.40
 Max. emission wavelength :423.6nm Max. absorption wavelength :364.1nm
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Photo Luminescence and absorption of bisMSBPhoto luminescence Fluorescence device: HORIBA

FluoroMax-4
 Absorbance device : HITACHI
U-3000 Solvent : Benzonitrile (PhCN) Concentration : 1.0×10-5 mol/L 1,4-Bis(2-methylstyryl)benzene
 Molecular mass : 310.44
 Max. emission wavelength :426.6nm
 Max. absorption wavelength :355.3nm
March 2nd, 2013

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