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

ジルコニウム９６を用いたニュートリノを放出しない二重ベータ崩壊の研究
新学術領域「宇宙の歴史をひもとく地下素粒子原子核研究」
第一回

宮城教育大学教育学部

福田研究会
善之、ナリンゲルラ、小畑東京大学宇宙線研究所

福井大学工学部
東京理科大学理工学部

森山 茂栄

小川

泉

郡司天博、塚田学

旭*第一回 地下素核研究 研究会

Aug 24th, 20142

NEUTRINOLESS DOUBLE BETA DECAY[T1/20n(0+ ->0+)]-1 =G0n(E0,Z)|M0n|2<mn>2
T1/2~a(Mt/DEB)

a: abundance

M: target masst: measurement time DE: energy resolution B: BG rate

Requirement : Low BG, Large target mass, High energyresolution
第一回 地下素核研究 研究会

Aug 24th, 2014

3ZIRCONIUM COMPLEX IN ORGANIC LIQUIDSCINTILLATOR FOR DOUBLE BETA DECAY
EXPERIMENT (ZICOS EXPERIMENT)
Goals ：
(1) Over 10w.t.% solubility(2) 60% light yield to BC505(3) 4% at 2.5MeV energy-resolution

3m

PMT with
40% photocoverage

Water shield surrounding
inner balloon to veto g’s

Zirconium loaded 100 tons LS(300kg 96Zr assuming10% enrich)
第一回 地下素核研究 研究会

10m
Aug 24th, 2014

4

ZIRCONIUM BETA-DIKETON COMPLEX
 Zirconium(IV)acetylacetonate (Zr(acac)4)

 Advantage
 good solubility (over10w.t.%) in Anisole(PhOMe)

MW: 487.66

 Stable and cheep Commercial product Disadvantage
 Low scintillation lightyield due to overlap
the absorption ofligand and emission ofanisole.

第一回 地下素核研究 研究会

Aug 24th, 2014

5

LIGHT YIELD AS A CONCENTRATION OFZIRCONIUM ACETYLACETONATE
concentrationof Zr(acac)4Observedchannel

Expectedchannel

0 mg

2450

2450

50mg

1800

1997

100mg

1400

1687

200mg

950

1284

300mg

650

1038

500mg

3007506
第一回 地下素核研究 研究会

Aug 24th, 2014ZIRCONIUM ΒETA-KETO ESTER COMPLEX
Zr(CH3COCHCOOCH(CH3)2)4Zr(CH3COCHCOOCH2CH3)4= Zr(iprac)4mw : 663.87= Zr(etac)4mw : 607.76

Expected shorter absorption wavelength
第一回 地下素核研究 研究会

Aug 24th, 2014

7

SYNTHESIZE OF ZIRCONIUM BETA-KETO ESTERCOMPLEXZr(iprac)4
state: powderZr(etac)4
state : dry solid

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

Solubility > 10 w.t.% for anisole
第一回 地下素核研究 研究会

Aug 24th, 20148

ABSORBANCE SPECTRA FOR ZIRCONIUM
BETA-KETO ESTER COMPLEXAbsorption tail of b-ketoester ligands slightlyoverlapped with theregion of the emission ofanisole.

第一回 地下素核研究 研究会

Aug 24th, 2014

9

LIGHT YIELD OF LS CONTAINING ZIRCONIUM
BETA-KETO ESTER COMPLEX
Light yield decreased
as increasing theconcentration of thecomplex even thoughsmall overlapping
between theabsorption of ligand
and the emission ofanisole .

第一回 地下素核研究 研究会

Aug 24th, 201410

BACK SCATTERING METHODSingle peak could be usedeven in liquid scintillator.
第一回 地下素核研究 研究会

Aug 24th, 201411

LIGHT YIELD OF LS CONTAINING ZIRCONIUMCOMPLEX AS A FUNCTION OF CONCENTRATIONLight yield of Zr(iprac)4even with small bumprecovered about double
compared with Zr(acac)4.
Light yield at 10w.t.%
concentration wasalmost 40% to BC505(≒ standard cocktail) .
It is slightly smaller
value than our goal...
第一回 地下素核研究 研究会

Aug 24th, 201412

ENERGY RESOLUTION OF LS CONTAININGZIRCONIUM COMPLEX AS A FUNCTION OF
CONCENTRATION
Photo coverage : ~8.5%(see explanation slide)
Assuming 40% of photo
coverage, the energy
resolution will recover
6.5% @ 1MeV = 4.1%
@ 2.5MeV for 10 w.t.%
concentration.
They almost achieved
to our initial goal!.
第一回 地下素核研究 研究会

Aug 24th, 2014

13

TETRAKIS (DIETHYL MALONATO) ZIRCONIUM
AND ABSORBANCE SPECTRUM OF LIGAND
Zr(CH3CH2OCOCHCOOCH2CH3)4= Zr(demｌ)4 mw : 727.87

shorter wavelength (~210nm)
第一回 地下素核研究 研究会

Aug 24th, 201414

LIGHT YIELD OF LS CONTAINING DIETHYL
MALONATO LIGAND
No quenching due tooverlap between theabsorption of ligand andthe emission of anisole
should be occurred.

Perfect!
第一回 地下素核研究 研究会

Zr(deml)4 will be an
ultimate complex if thesolubility could be over
10w.t.% for anisole.
Aug 24th, 201415

SUMMARY ZICOS uses liquid scintillator containing zirconium

complex for neutrinoless double beta decay search Confirmed that the absorption peak moved shorter

wavelength (275nm → 245nm) by introducing b-ketoester substituent groups.

 Succeeded anisole based liquid scintillator with 10w.t.% concentration of Zr(iprac)4 which has both 40%
for light yield to BC505 and 4.1%@2.5MeV (assuming40% photo coverage) for energy resolution, so thatthey almost achieved our initial goal !

 To improve light yield (and also energy resolution) , weshall move the absorption peak around 210nm usingZr(deml)4 “tetrakis (diethyl malonato) zirconium”.

第一回 地下素核研究 研究会

Aug 24th, 201416

BACKUP

第一回 地下素核研究 研究会

Aug 24th, 201417

ATTENUATION LENGTH OF ANISOLE
Attenuation length oflight from POPOP wasobtained as ~6m. It isalmost equivalent withthe detector size.

第一回 地下素核研究 研究会

Aug 24th, 201418

ABSORBANCE SPECTRA FOR ZIRCONIUM
BETA-KETO ESTER COMPLEXAbsorption peaks ofzirconium b-keto ester
complex were foundaround at 245nm.
Also small bump was
found around 280nm
due to impurities whichmight be made by thevapor.
第一回 地下素核研究 研究会

Aug 24th, 201419

ABSORBANCE SPECTRA OF ZIRCONIUM
BETA-KETO ESTER COMPLEX
No bump appeared for
initial complex.
Small bump might bemade by vapor in the air,because no bump was
found for complex storedin solvent.

第一回 地下素核研究 研究会

Aug 24th, 201420

ABSORBANCE SPECTRA OF ZIRCONIUM BETAKETO ESTER COMPLEX FOR VARIOS POSITION
Small bump disappearedafter ~ 1 week.
These could be some
impurities of Zr complex
and they precipitated onbottom of the vial.

第一回 地下素核研究 研究会

Aug 24th, 201421

ABSORBANCE SPECTRA FOR ZIRCONIUM
BETA-KETO ESTER COMPLEX AFTER 1 WEEK
Small bump disappeared
after ~ 1 week.
It could be explained by
impurities of Zr complex,
and they should beprecipitated on bottom ofthe vial.

(see explanation slide)
第一回 地下素核研究 研究会

Aug 24th, 201422

ABSORBANCE SPECTRA FOR ZIRCONIUM
BETA-KETO ESTER COMPLEX IN ANISOLE
Small bump around
280nm in anisole did notdisappear even after ~ 1week.
Impurities might bedissolved in anisole…
We have to purify thecomplex by using suchas sublimation.
第一回 地下素核研究 研究会

Aug 24th, 201423

ABSORPTION SPECTRA FOR SEVERALSOLVENT Absorption spectra ofZr(iprac)4 changes.

第一回 地下素核研究 研究会

Aug 24th, 201424

ABSORPTION SPECTRA

第一回 地下素核研究 研究会

Aug 24th, 201425

LIGHT YIELD OF LS CONTAINING BETA-KETO
ESTER LIGAND
Light yield recovered
about 50% comparedto the Zr-keto ester
complex due to vanish
the small bump.
However, a quenchingoccurred due to theabsorption tail.

第一回 地下素核研究 研究会

Aug 24th, 201426

PHOTO COVERAGE
Scintillation light wasguided to PMT via theacrylic light guide.
From the computer
simulation, the solid
angle was obtained as
8.5% for 4p area.

第一回 地下素核研究 研究会

Aug 24th, 201427

PHOTO COVERAGE
Scintillation light wasguided to PMT via theacrylic light guide.
From the computer
simulation, the solid
angle was obtained as
8.5% for 4p area.

第一回 地下素核研究 研究会

Aug 24th, 201428

Light yield calculation
Light yield = L0 ×s1Nppo
s1Nppo + s2NZr

L0 : Light yield of anisole
Nppo : No. of PPO molecular
NZr : No. of complex moleculars1: absorbance of PPO
s2 : absorbance of complex

第一回 地下素核研究 研究会

Aug 24th, 2014

29

WHAT’S PROBLEM
 Absorption spectra ofIn(acac)3 (indium acetylacetone) was overlappedwith the emission spectrafrom Anisole （Chem. Phys.
Lett., 435(2007), 252)

Same overlap between the emission
and the absorption could be occurred
even if different metal (Zr) was used.
第一回 地下素核研究 研究会

Aug 24th, 201430

PHOTO LUMINESCENCE AND ABSORPTION OFPPO Photo luminescence Fluorescence device: HORIBA

FluoroMax-4

 Absorbance device : HITACHI

U-3000 Solvent : Benzonitrile (PhCN) Concentration : 1.0×10-5mol/L 2,5-Diphenyloxazole

 Molecular mass : 221.26
 Max. emission wavelength :368.0nm

 Max. absorption

wavelength : 309.7nm

第一回 地下素核研究 研究会

Aug 24th, 201431

PHOTO LUMINESCENCE AND ABSORPTION OFPOPOP Photo luminescence Fluorescence device: HORIBA

FluoroMax-4

 Absorbance device : HITACHIU-3000

 Solvent : Benzonitrile (PhCN) Concentration : 1.0×10-5mol/L 1,4-Bis(5-phenyloxazol-2-yl)benzene

 Molecular mass : 364.40
 Max. emission wavelength :423.6nm

 Max. absorption

wavelength : 364.1nm

第一回 地下素核研究 研究会

Aug 24th, 201432

PHOTO LUMINESCENCE AND ABSORPTION OFBIS-MSB
 Photo luminescence Fluorescence device: HORIBA

FluoroMax-4

 Absorbance device : HITACHI

U-3000 Solvent : Benzonitrile (PhCN) Concentration : 1.0×10-5mol/L 1,4-Bis(2-methylstyryl)benzene

 Molecular mass : 310.44
 Max. emission wavelength :426.6nm Max. absorption

wavelength : 355.3nm

第一回 地下素核研究 研究会

Aug 24th, 201433

FOR FUTURE EXPERIMENTS

high energyresolution
4%@2.5MeV

F.Piquemal@n2012

http://kds.kek.jp/getFile.py/access?contribId=37&sessionId=16&resId=2&materialId=slides&confId=9151~tons of target will be necessary for next generation detector
第一回 地下素核研究 研究会

Aug 24th, 201434