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 （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
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 Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
Concepts of CANDLE S system Concepts of CANDLE S system Undoped CaF 2 crystals immersed in a liquid scintillator CaF 2 crystal • CaF 2 (pure) crystal + w.l. shifter Buffer oil – Long attenuation length large scale detector • Liquid scintillator – 4 π active shield • Difference in decay time of signal 900 nsec : CaF 2 (pure) a few × 10 nsec : liquid scintillator – WLS liquid scintillator • Convert UV light from CaF2(pure) to visible light 13" PMT Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
CaF CaF (E (E u) and CaF u) and CaF (pure) (pure) CaF CaF 2 (E (E u) and CaF u) and CaF 2 (pure) (pure) 2 2 • CaF 2 (Eu) Scintillation emission spectra of CaF 2 crystal – Commonly used scintillator 1.0 50 CaF 2 (pure) CaF 2 (Eu) – 24 photons / keV 0.8 40 – λ emission = 420 nm ) . Borosilicate u 0.6 30 . UV a Q.E. (%) ( y t – Self absorption i s n e 0.4 20 t n I 0.2 10 • CaF 2 (pure) 0.0 0 – Commonly used as lens 200 300 400 500 600 Wavelength (nm) – Good transparency • CaF 2 (Eu) : from BICRON catalogue – Can be used as scintillator • CaF 2 (pure) : measured value – ~10 photons / keV – λ emission = 285 nm Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
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 Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
Requirements for liquid scintillator (1) quirements for liquid scintillator (1) Requirements for liquid scintillator (1) quirements for liquid scintillator (1) • Photon collection of CaF 2 (pure) – WLS • UV light from CaF 2 (pure) sensitive region (visible light) of PMTs • Short fluorescent lifetime PSD for – not distort pulse shape of CaF 2 (pure) BG rejection – Base solvent • Transparent to UV light from CaF 2 (pure) • Refractive index: closed to that of CaF 2 (pure) – avoid optical loss at a boundary Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
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 Mineral • Simple mixture oil base • 4 π active shield with aromatic – large light output solvents – highly transparent against its light • Long term and safe operation – high flush point – chemical stability Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
Aromatic solvents Aromatic solvents Aromatic solvents Aromatic solvents To increase light output of LS aromatic solvents λ max (nm) τ F (nsec) solvent Q.Y. absorption emission benzene (C 6 H 6 ) 0.07 29 255 280 toluene (C 7 H 8 ) 0.17 34 260 285 p-xylene (C 8 H 10 ) 0.40 30 270 285 m-xylene (C 8 H 10 ) 0.17 30.8 270 285 o-xylene (C 8 H 10 ) 0.19 32.2 265 285 ethyl-benzene (C 8 H 10 ) 0.18 31 260 285 mesithylene (C 9 H 12 ) 0.17 36.5 275 290 pseudocumene (C 9 H 12 ) 0.41 27.2 270 290 cumene (C 9 H 12 ) 0.12 22 260 280 absorption in UV region Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
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 Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
Two Phase System Two Phase System Two Phase System Two Phase System Concept of Method • Conversion Phase – Large conversion eff. – good transparency for UV • Veto Phase – Large light output with CaF 2 (Pure) aromatic solvent CaF 2 Emission (~280nm) Conversion by WLS(350~400nm) propagate PMT Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
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 output Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
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 Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
Optimization of WLS Optimization of WLS Optimization of WLS Optimization of WLS Investigated Solute τ F (nsec) Solute Q.Y. p-Terphenyl 0.93 1.21 PPO 0.84 1.44 bis-MSB 0.94 1.24 α -NPO 0.94 2.06 Dimethyl-POPOP 0.93 1.50 Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
LS for conversion phase LS for conversion phase LS for conversion phase LS for conversion phase • absorption/emission curve bis-MSB p-Terphenyl PPO α -NPO Dimethyl-POPOP Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
Results Resu lts Resu Results lts • Pulse height spectra p-Terphenyl PPO bis-MSB α -NPO Dimethyl-POPOP Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
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 liquid scintillator CaF 2 crystal γ source Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
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 Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
Performance Test (conversion phase) Performance Test (conversion phase) Standard γ Source Side View CaF 2 (pure) 10 × 10 × 10 cm 3 R = 3.5 % @ Q -value Liquid Scintillator (conversion phase; 7mm) 3000 Counts 1500 137 Cs (662keV) 60 Co (1333keV) 2500 1250 9.14%(FWHM) 2000 1000 5.91%(FWHM) 1500 750 1000 500 500 250 0 0 0 200 400 600 800 1000 0 250 500 750 1000 1250 1500 1750 Energy (keV) Energy (keV) Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
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 Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
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 LS of CaF 2 (pure) – acrylic vessel dissolved in PC 20 vol% of PC in P250 Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
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 Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
Attenuation length length Attenuation Cylindrical Acrylic case 200cm Long 0.3cm LS for veto phase sim. w/o atten. 9.7 ± 1.3 m exp. Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
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 Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
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 Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
Performance of two phase system Performan e of two phase system Performan Performance of two phase system e of two phase system • Thick (5 cm) conversion phase only small photo 137 Cs coverage Liquid Scintillator for PMT(5") × 4 Conversion Phase CaF 2 (pure) Liquid Scintillator for CANDLES System 小川 泉 September 19, 2005
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