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Liquid S Liquid Scintillator for CANDLE cintillator for CANDLE cintillator for CANDLE S System S System Liquid S Liquid S cintillator for CANDLE S System S System OGAWA Izumi Graduate School of Science, Osaka University

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SLIDE 1

Liquid S Liquid S Liquid S Liquid Scintillator for CANDLE S System cintillator for CANDLE S System cintillator for CANDLE S System cintillator for CANDLE S System

OGAWA Izumi （小川 泉）

Graduate School of Science, Osaka University （大阪大学 大学院理学研究科）

CANDLES Collaboration: Osaka Univ. : R. Hazama, Y. Hirano, K. Ichihara, T. Kishimoto,

  • K. Matsuoka, S. Umehara, D. Yokoyama, S. Yoshida
  • Univ. of Tokushima : K. Fushimi

Saga Univ. : H. Ohsumi

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SLIDE 2

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Outline Outline Outline Outline

  • Introduction – CANDLES –
  • Requirements for liquid scintillator
  • Two phase system

– LS for conversion phase – LS for veto phase – Performance of two phase system

  • Summary
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SLIDE 3

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Concepts of CANDLE S system Concepts of CANDLE S system

Undoped CaF2 crystals immersed in a liquid scintillator

  • CaF2(pure) crystal

– Long attenuation length large scale detector

  • Liquid scintillator

– 4π active shield

  • Difference in decay time of signal

900 nsec : CaF2(pure) a few×10 nsec : liquid scintillator

– WLS

  • Convert UV light from CaF2(pure)

to visible light

Buffer oil liquid scintillator CaF2 crystal + w.l. shifter 13" PMT

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SLIDE 4

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

CaF CaF CaF CaF

2 2(E

u) and CaF (E u) and CaF (E u) and CaF (E u) and CaF

2 2(pure)

(pure) (pure) (pure)

  • CaF2(Eu)

– Commonly used scintillator – 24 photons / keV – λemission = 420 nm – Self absorption

  • CaF2(pure)

– Commonly used as lens – Good transparency – Can be used as scintillator – ~10 photons / keV – λemission = 285 nm

0.0 0.2 0.4 0.6 0.8 1.0 10 20 30 40 50 200 300 400 500 600 CaF2(pure) CaF2(Eu) Borosilicate UV

Wavelength (nm) I n t e n s i t y ( a . u . ) Q.E. (%)

Scintillation emission spectra of CaF2 crystal

  • CaF2(Eu) :

from BICRON catalogue

  • CaF2(pure) : measured value
slide-5
SLIDE 5

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Outline Outline Outline Outline

  • Introduction – CANDLES –
  • Requirements for liquid scintillator
  • Two phase system

– LS for conversion phase – LS for veto phase – Performance of two phase system

  • Summary
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SLIDE 6

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Requirements for liquid scintillator (1) quirements for liquid scintillator (1) Requirements for liquid scintillator (1) quirements for liquid scintillator (1)

  • Photon collection of CaF2(pure)

– WLS

  • UV light from CaF2(pure)

sensitive region (visible light) of PMTs

  • Short fluorescent lifetime

– not distort pulse shape of CaF2(pure)

– Base solvent

  • Transparent to UV light from CaF2(pure)
  • Refractive index: closed to that of CaF2(pure)

– avoid optical loss at a boundary PSD for BG rejection

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SLIDE 7

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Requirements for liquid scintillator (2) quirements for liquid scintillator (2) Requirements for liquid scintillator (2) quirements for liquid scintillator (2)

  • Passive shield

– large quantity with reasonable costs

  • Low background

– purification

  • Simple mixture
  • 4π active shield

– large light output – highly transparent against its light

  • Long term and safe operation

– high flush point – chemical stability Mineral

  • il base

aromatic solvents

with

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SLIDE 8

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Aromatic solvents Aromatic solvents Aromatic solvents Aromatic solvents To increase light output of LS aromatic solvents

emission absorption 280 260 22 0.12 cumene (C9H12) 290 270 27.2 0.41 pseudocumene (C9H12) 290 275 36.5 0.17 mesithylene (C9H12) 285 265 32.2 0.19

  • -xylene (C8H10)

285 270 30 0.40 p-xylene (C8H10) 280 255 29 0.07 benzene (C6H6) 285 260 31 0.18 ethyl-benzene (C8H10) 285 270 30.8 0.17 m-xylene (C8H10) 285 260 34 0.17 toluene (C7H8) λmax (nm) τF (nsec) Q.Y. solvent

absorption in UV region

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SLIDE 9

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Outline Outline Outline Outline

  • Introduction – CANDLES –
  • Requirements for liquid scintillator
  • Two phase system

–LS for conversion phase

– LS for veto phase – Performance of two phase system

  • Summary
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SLIDE 10

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Two Phase System Two Phase System Two Phase System Two Phase System

CaF2(Pure)

Concept of Method

  • Conversion Phase

– Large conversion eff. – good transparency for UV

  • Veto Phase

– Large light output with aromatic solvent

CaF2 Emission (~280nm) Conversion by WLS(350~400nm) PMT propagate

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SLIDE 11

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Requirements for two phase system Requirements for two phase system Requirements for two phase system Requirements for two phase system

  • Thickness of conversion phase

– As thin as possible – BG rejection efficiency is worse in conversion phase because of its low light

  • utput
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SLIDE 12

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

LS for conversion phase LS for conversion phase LS for conversion phase LS for conversion phase

  • Solvents

– Paraol250

good transparency in UV region

SK Data

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SLIDE 13

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Optimization of WLS Optimization of WLS Optimization of WLS Optimization of WLS

Investigated Solute

1.50 0.93 Dimethyl-POPOP 2.06 0.94 α-NPO 1.24 0.94 bis-MSB 1.44 0.84 PPO 1.21 0.93 p-Terphenyl τF (nsec) Q.Y. Solute

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SLIDE 14

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

LS for conversion phase LS for conversion phase LS for conversion phase LS for conversion phase

  • absorption/emission curve

p-Terphenyl PPO bis-MSB α-NPO Dimethyl-POPOP

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SLIDE 15

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Resu Results lts Resu Results lts

  • Pulse height spectra

p-Terphenyl PPO bis-MSB α-NPO Dimethyl-POPOP

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SLIDE 16

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Thickness of Conversion phase Thickness of Conversion phase Thickness of Conversion phase Thickness of Conversion phase

  • 5 mm thickness is sufficient

bis-MSB Dimethyl-POPOP

γ source liquid scintillator CaF2 crystal

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SLIDE 17

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Mixture for conversion phase Mixture for conversion phase Mixture for conversion phase Mixture for conversion phase

  • Solvent

– Mineral Oil (Paraol250)

  • WLS

– bis-MSB 0.1 g/l good solubility in Mineral Oil

  • Thickness

– 5 mm

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SLIDE 18

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Performance Test (conversion phase) Performance Test (conversion phase)

Side View CaF2(pure) 10×10×10 cm3

Standard γ Source

R = 3.5 % @ Q-value

Liquid Scintillator

250 500 750 1000 1250 1500 200 400 600 800 1000

9.14%(FWHM) Energy (keV) Counts

500 1000 1500 2000 2500 3000 250 500

60Co (1333keV) 137Cs (662keV)

(conversion phase; 7mm)

750 1000 1250 1500 1750

Energy (keV) 5.91%(FWHM)

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SLIDE 19

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Outline Outline Outline Outline

  • Introduction – CANDLES –
  • Requirements for liquid scintillator
  • Two phase system

– LS for conversion phase – LS for veto phase – Performance of two phase system

  • Summary
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SLIDE 20

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

LS for veto phase(1) LS for veto phase(1) LS for veto phase(1) LS for veto phase(1)

Solvent

  • Pseudocmene in Mineral Oil

– long attenuation length – high chemical stability – refractive index close to that

  • f CaF2(pure)

– acrylic vessel dissolved in PC

20 vol% of PC in P250

LS

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SLIDE 21

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

LS for veto phase(2) LS for veto phase(2) LS for veto phase(2) LS for veto phase(2)

Solute

  • PPO (P250(0.8)+PC(0.2))

– 1.0 g/l

  • bis-MSB (P250(0.8)+PC(0.2)+PPO(1.0 g/l))

– 0.1 g/l Same WLS in conversion phase

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SLIDE 22

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Attenuation Attenuation length length

Cylindrical Acrylic case

200cm Long

0.3cm

exp. sim. w/o atten. 9.7 ± 1.3 m LS for veto phase

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SLIDE 23

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Mixture for Veto phase Mixture for Veto phase Mixture for Veto phase Mixture for Veto phase

  • Solvent

– Mineral Oil (Paraol250) 80 vol% – Pseudocumene 20 vol%

  • WLS

– PPO 1.0 g/l – bis-MSB 0.1 g/l

  • Attenuation length

– 9.7 m w/o purification

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SLIDE 24

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Outline Outline Outline Outline

  • Introduction – CANDLES –
  • Requirements for liquid scintillator
  • Two phase system

– LS for conversion phase – LS for veto phase – Performance of two phase system

  • Summary
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SLIDE 25

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Performan Performance of two phase system e of two phase system Performan Performance of two phase system e of two phase system

  • Thick (5 cm) conversion phase only

CaF2(pure) Liquid Scintillator for Conversion Phase PMT(5")×4

small photo coverage

137Cs

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SLIDE 26

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Performan Performance of two phase system e of two phase system Performan Performance of two phase system e of two phase system

  • Two Phase system (5 mm conversion phase)

CaF2(pure) Liquid Scintillator for Conversion Phase PMT(5")×4 Liquid Scintillator for Veto Phase

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SLIDE 27

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Performance Test Performance Test (Veto)

(Veto)

events from LS events from CaF2

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SLIDE 28

September 19, 2005

Liquid Scintillator for CANDLES System 小川 泉

Summary Summary Summary Summary

  • LS in CANDLES System

– complete 4π active shield – WLS for emission from CaF2(pure)

  • Two Phase System

– conversion phase

  • Paraffin oil (Paraol250) + bis-MSB (0.1 g/l)
  • 5 mm in thickness

– veto phase

  • P250(80 vol%) + PC(20 vol%) + PPO(1.0 g/l) + bis-MSB(0.1 g/l)
  • long attenuation length; 9.7 m (without purification)
  • large light output response; ~7×103 photons/MeV
  • In CANDLES System

– Energy resolution of CaF2(pure); ~4 % @ Q-value – light output in Veto phase; ~500 photoelectrons/MeV