Reactor Experiment for Neutrino Os-cillation

Liquid Scintillator R&DJS Park for RENO Collaboration

□ Transparency□ High light yield□ Long term stability□ High radiopurity □ Safety matter□ Reasonable price□ Massive quantity available

Liquid Scintillator ingredients: Base solvent + primary scintillating fluor + secondary wavelength shifter

Effect of wavelength shifter

Before

After

PMT sensitive region

•Internal background material : 238U, 232Th, 40K

• PMT glass is dominant internal background material : ~10Hz

• LS radioimpurity contribute to background : ~2Hz (10-12 g/g)

Sample Th U

ICP-MS(g/g)

1.1E-12 8E-13

MC simulation of internal background

E4Lm

sin)2(sincosE4

Lmsin)2(sin1)(P

2212

122

134

2312

132

ee

IntroductionTheta 13 measuring Experiment□ Two Identical Detectors : Lower Experimental errors : ~1% level !!□ Power Reactors : 6-core□ Large Volume Detector : 15 tons□ Lower Background : Increase overburden

Reaction in the Detector Detector Configuration

Inverse Beta Decay

Delayed signal

prompt signal

enpe

Neutron captured by Gadolinium

P n

Gd Total E~8MeV

Target : Gd-LSCatcher : LSBuffer : Mineral-OilVeto : Water

4-cylindrical detector

Base solvent For mixing FluorWave-length

shifter

PC , LAB MO, Dodecane PPO, BPO bis-MSB, POPOP

General Elements of Liquid Scintillator

Gd-CBX

Liquid Scintillator

Gd-CBX synthesis process

Gd-CBX precipitated !!

Reaction equation

1. RCOOH + NH3•H2O ->RCOONH4 + H2O

2. 3RCOONH4(aq) + GdCl3*6H2O -> Gd(RCOO)3 + 3NH4Cl

Gd-CBX powder was rinsed with 18MΩ water for several times and dried in vacuum desiccator.

We can check whether we truly make Gd-CBX power with FT-IR Spectroscopy.1. No OH group (3200~3500)2. No free acid peak (~1700)3. We have Carboxylic peak (~1420, ~1580)

Quality check

pH 7.4

pH 6.5

pH 6.2

pH 6.0

pH 5

pH 9.7

pH 7.5

pH 7.2

OH group

Free acid peak

After reaction pH Neutralization pH

□ Gd have large neutron capture cross section : ~49000 barn□ Gd needs to transform to Gd-CBX for loading into organic phase

Gd to Gd-CBX

Gd-CBX powder for RENO Detector

FT-IR Graph

Carboxylic peak

No OH Group

No Free Acid

□ Final Gd-CBX powder□ After grinding, store in a petri dish

Loading into LAB and purity□ We can load Gd-CBX into LAB by 0.1% (1g/L).□ ~ 95% of purity has been achieved.

Required PropertiesLY saturated when PPO 3g/L and bis-MSB 30mg/L

Bis-MSB

PPO

Fluor Optimization

20mL Liquid Scintillator

Reference - CsI Crystal with3cm*3cm*3cm

Compton edge

Photo peak

Light Yield Measurement Radioactive Background

ICP-MS result of radioimpurity

Using Cs source : 0.662MeV

~30us

θ13 Dominant

θ12 Dominant

Near DetectorFar Detector

Survival probability with respect to baseline(L)

Compton edge