Supported by Grant-in-Aid for Scientific Research (C) 24540295 andGrant-in-Aid for Scientific Research on Innovative Areas 24104501 and 26105502

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事象の探索Ⅴ
日本物理学会

2014年秋季大会

2014年9月20日
宮城教育大学教育学部

福田善之、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*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
日本物理学会 2014年秋季大会

Sep 20th, 2014

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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)
日本物理学会 2014年秋季大会

10m
Sep 20th, 2014

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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.

日本物理学会 2014年秋季大会

Sep 20th, 2014

4

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

300

750

5
日本物理学会 2014年秋季大会

Sep 20th, 2014

ZIRCONIUM ΒETA-KETO ESTER COMPLEXZr(CH3COCHCOOCH(CH3)2)4Zr(CH3COCHCOOCH2CH3)4= Zr(iprac)4
mw : 663.87= Zr(etac)4mw : 607.76

Expected shorter absorption wavelength
日本物理学会 2014年秋季大会

Sep 20th, 2014

6

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

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

Solubility > 10 w.t.% for anisole
日本物理学会 2014年秋季大会

Sep 20th, 20147

ABSORBANCE SPECTRA FOR ZIRCONIUM
BETA-KETO ESTER COMPLEX
Absorption tail of (pure)zirconium b-keto ester
complex slightlyoverlapped with theregion of the emission ofanisole. (No bumparound 270nm was seen.
See next talk)
日本物理学会 2014年秋季大会

Sep 20th, 20148

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 .

日本物理学会 2014年秋季大会

Sep 20th, 2014

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LIGHT YIELD OF LS CONTAINING ZIRCONIUMCOMPLEX AS A FUNCTION OF CONCENTRATIONLight yield of Zr(iprac)4
recovered 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...
日本物理学会 2014年秋季大会

Sep 20th, 201410

LIGHT YIELD OF LS CONTAINING COMPLEX AND
LIGAND AS A FUNCTION OF CONCENTRATION
Both light yields ofZr(iprac)4 and Zr(etac)4
are almost same. They
are also about half yieldfor those ligand.
It is due to small bumparound 270nm (seenext talk).
日本物理学会 2014年秋季大会

Sep 20th, 201411

ENERGY RESOLUTION OF LS CONTAINING
LIGAND 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!.
日本物理学会 2014年秋季大会

Sep 20th, 2014

12

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

shorter wavelength (~210nm)
日本物理学会 2014年秋季大会

Sep 20th, 201413

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

Perfect!
日本物理学会 2014年秋季大会

Zr(deml)4 will have anenergy resolution of
2.9% @ 2.5MeV for
10w.t.% concentration.
Sep 20th, 2014

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SYNTHESIS OF TETRAKIS (DIETHYL MALONATO)ZIRCONIUM

Absorbance spectra ofZr(deml)4 and diethyl
malonate are almost same.
日本物理学会 2014年秋季大会

Sep 20th, 201415

SUMMARY ZICOS uses liquid scintillator containing zirconium

complex for neutrinoless double beta decay search.

 Confirmed that the absorption peak was moved toshorter wavelength (275nm → 245nm) by introducing
b-keto ester substituent groups.

 Possible to anisole based liquid scintillator be 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 will be almost achieved our initial goal !

 To improve both light yield and also energy resolution ,we shall move the absorption peak around 210nm
using Zr(deml)4 and will get 2.9% @ 2.5MeV!

日本物理学会 2014年秋季大会

Sep 20th, 201416