1. Summary of Gd+Liquid Scintillator 김수봉, 박정식, 이재승 ( 서울대학교 ) 서준석 ( 경북대학교 ) 유인태 ( 성균관대학교 ) 주경광, 김선희 ( 전남대학교 ) 9 th RENO Collaboration Meeting at SNU Oct. 10~11, 2008 RENO LS Subgroup Collaboration 주경광 ( 전남대 )

2. RENO Detector Buffer with PMT Front view Side view RENO detector consists of four concentric cylindrical containers. 384 PMTs

3. Liquid Scintillator at a Glimpse Transparency High light yield Long term stability High radiopurity Safety matter Reasonable price Massive quantity available Base solventFor mixingFluor Wave-length shifter PC, PXEMO, DodecanePPO, BPObis-MSB, POPOP Base solvent + primary scintillating fluor + secondary wavelength shifter Required Properties General elements of Liquid Scintillator Effect of wavelength shifter Before After PMT sensitive region PC is widely used for base solvent for its excellent transparency and fluor dissolution.

4. RENO Base Liquid Scintillator  PC(20%) + dodecane(80%) + PPO(3g/L) + bis-MSB(30mg/L) Gd-LS R&D with the Russian INR/IPCE group : Gd-LS stability: good for > 6 months Performance study of various LS recipes : : light yield : Optical properties (transmission & attenuation lengths, etc.) Development of purification system to enhance optical properties & reduce radioactive materials. : Al 2 O 3 adsorption : Vacuum distillation : Water extraction, etc Long-term stability test Reactivity test with acrylic Study of Linear Alkyl Benzene(LAB) for replacing PC. Purification with Al 2 O 3 Before After Transparency can be increased by purification.

5. LAB(Linear Alkyl Benzene) C n H 2n+1 -C 6 H 5 (n=9~14) PCLAB Molecular formulaC 9 H 12 C n H 2n+1 -C 6 H 5 Molecular weight(g/mol)120.19233~237 Flash point (°C)48130 Density(g/ml)0.890.86 Compatibility(acryllic)Negative, need diluentTest in progress CostModerateCheap Fluor dissolutionVery goodModerate Domestic availabilityAbroadAvailable etcHarmful odorColorless & odorless LAB nPercent(%) 90.47 109.7 1133.85 1234.72 1320.83 140.43 GC-MS result of LAB Light Yield Comparison 4 main component

6. Optimization of PPO & bis-MSB Concentration Light Yield Measuremen t LY saturated when PPO 3g/L and bis-MSB 30mg/L Bis-MSB PPO

7. Optimization of PPO & bis-MSB Concentration Light Yield Measuremen t LY saturated when PPO 3g/L and bis-MSB 30mg/L Bis-MSB PPO

8. Problems reported CHOOZ 실험에서 - 5t 0.09% Gd-loaded scintillators - 변색문제 : Not stable (turned yellow after few months of deployment) ~250 일 경과 후 ) - 출력감소 문제 : Degradation of its optical properties. 즉, very rapid decay of attenuation length 관측됨. ~0.4% degradation/day 또한, Palo Verde 실험에서도 비슷한 결과가 보고됨 - 12t 0.1% Gd-loaded scintillators - Slight deterioration with time - ~0.03% degradation/day Gd-doped Liquid Scintillator Chemistry

9. Gd -CBX Precipitated Gd-CBX powder was filterated and rinse with 18MΩ water several times and dried in desiccator. After filteration Stored in bottle Gd needs to transform to Gd-CBX for loading in organic phase Gd-CBX precipitated Reaction equation RCOOH + NH 3 H 2 O ->RCOONH 4 + H 2 O 3RCOONH 4 (aq) + GdCl 3 (aq) -> Gd(RCOO )3 + 3NH 4 Cl

10. FT-IR 에 의한 Gd-TMHA 성분분석 FT-IR( Fourier Transform Infrared Spectroscopy, 적외선 분광법 ) 적외선을 시료에 주사하면 시료의 분자운동에 의한 적외선 흡수가 발생하고 흡수된 적외선 스펙트럼을 얻어 시료를 분석하는 장치

11. 만족 시켜야 할 조건 1.OH group 유무 - FT-IR 3200~3500 사이에 peak 나타남. 2. Free acid peak 유무 - FT-IR ~1700 근방에 peak 나타남. 3. Carboxylic peak 유무 - ~1420 & 1580 근방에 peak 나타남. 4. Gd loading into LAB Gd-(TMHA) 3 powder 제조가 목적 Gd-OH 는 불순물로 작용. 이유 여분의 TMHA 가 남아있는 것. 물로 세척 할 때 씻겨나가지 않는다.  불순물로 작용. Gd-TMHA 가 만들어 진것을 나타내는 증거 성공적인 RENO 실험을 위해 Requirements for Gd-TMHA

12. 결정 요인 : after reaction 의 pH 값 pH 7.4 pH 6.5 pH 6.2 pH 6.0 After reaction pH ~ 6.0 이하로 제작해야 OH peak 이 보이지 않는다. Carboxylic -1420 & 1580 OH -3200~3500 Peak position Free Acid -1710 OH peak OH group

13. 결정 요인 : 중화반응 시 남는 여분의 TMHA 의 유무 TMHA 과량 NH 3 다량 과량 NH 3 미량 과다 Almost 1:1 중화반응 시 NH 3 양이 더 많아야 함 : pH > 7 pH ~5 pH ~7.2 pH ~7.5 pH ~9.7 Free acid peak Free acid

14. R&D 결과 - pH control 이 중요 - After reaction pH ~ 6 After reaction pH 결정 요인 - Gd 수용액 pH 4.5~5 - 중화반응 pH > 7 8:8Sample 1 sample 2 Sample 3 sample 4 sample 5 Sample 7 Sample 10 sample 13 GdCl 3 *6H 2 ON/A2.01542.0072.0122.0081.60882.4032.00132.0072 Gd pHN/A55555555 중화 pH N/A87.58 7.27 After reactionN/A6.95.66.76.57.46.26.06.47 Purity ( 질산 ) 122102.895.7102.798.797.595.793.294.2 Sample lists OH group OH group + 염 과다 Worst Gd-TMHA Samples Best sample Sample 10 PH 배합이 가장 promising

15. Sample 10 LAB loading 적정 결과 : 2.81 g/L 까지 해봄 LAB 에 문제없이 loading 됨 Gd Loading in LAB Reproduce pH 6.0 pH 6.47 pH 6.83 Sample 10-1 - LAB loading 적정 : 92.4% - 질산 적정 : 94.3% - LAB / 질산 = 0.98 Sample 10-2  비교 sample - LAB loading 적정 : 93.8% - 질산 적정 : 94.9% - LAB / 질산 = 0.99

16. Vol(L)Flow Rate Target1532 L/min G.Cat cher 11206 L/min Buffer688924 L/min Flow rate to keep same level GdLS 200L LS 200L MO 200L Mockup 123 N2N2 N2N2 N2N2 Accumulate Flow Meter Magnetic Pump Schematic Design of LS Handling System for Mockup

17. Mixing Tank + Capacity : 200 L + Material : P.E. 3 tanks for Target, Gamma Catcher and Buffer. All tubing for liquid transportation is made from Teflon. N2 purging with Ф6 Teflon tubing MO 고순도 LAB

18. Production of LS for Mockup Baseline LS cocktail : –PPO(3g/L) + bis-MSB(30mg/L) + LAB PPO, bis-MSB 20 배 농축 일의 효율성증가 1 회 200L LS 생산한 후 filling 시작예정 –LAB (190L) + 20 times concentrated LS (10L) : with circulation mixing method –20 times concentrated LS = LAB (10L) + PPO (600g) + bis-MSB (6g) 목표량 : 200L of LS / a day ( 총 4 일정도 소요 )

19. Summary LAB is promised material to replace PC, dodecane. (e.g. Optical properties, radiopurity, …) Concentrations of PPO and bis-MSB for Liquid Scintillator are optimized. Light yield was measured in special dark box using Compton edge. Long term stability test will be carried out. Gd-TMHA 제작 R&D + Mock-up sample recipe 확정. Reproduce & quality control 진행 중 RENO 검출기를 위한 대량 생산 준비 Mock-up 용 powder 준비기간 + R&D 끝나면 대량 생산 시작 + 하루 ~80g 생산 예정 ( 제작에 2 주 소요될 것으로 예상됨 )