1. Update of Gd-LS R&D at IHEP Ding Yayun, Zhang Zhiyong, Cao Jun Institute of High Energy Physics, Chinese Academy of Sciences

2. Quality Requirements for Gd-LS – long attenuation length – good light yield – chemically compatible with acrylic – stable for several years Two main concerns in the preparation of Gd-LS – to find out the suitable solvents – to find out the suitable Gd complexes with organic ligands

3. Choice of Solvents  pseudocumene, PC and mesitylene Drawbacks: low flash point aggressive to acrylic  Linear alkylbenzene, LAB high light yield, high flash point, low toxicity, cheap long attenuation length

4. Linear alkylbenzene, LAB, C10~C13  Produced by JinLing Petrochemical Limited Corp., SINOPEC Crop. P.R.C  Meet national standards GB/T 5177.5-2002  Elemental analysis shows: C: 87.3% H: 11.5% (deviation: 1~3%) The most possible average molecular formula is C 6 H 5 -C 12 H 25  Further study about the composition of LAB is ongoing.

5. Requirements for the Selected Gd Complexes – stable enough against hydroylsis – relatively high solubility in aromatic solvent – low absorption around 430 nm – Organophosphorous compounds –  -Diketones – Carboxylic acids Three kinds of organic ligands have been used Choice of Gd Complexes

6. Organophosphorus Ligands Triethylphosphate (TEP) Triisoamylphosphine Oxide (TiAPO) Dibutylbutylphosponate (DBBP) Tri-n-octylphosphine oxide (TOPO) Di(2-ethylhexyl) phosphate (D2EHP) -Highly soluble in aromatic solvents -Moderate attenuation length Gd 3+

7.  -Diketone Acetylacetone (Acac) Chooz-II Low solubility in the scintillator solvent Gd 3+

8. Carboxylic acids 2-Methylvaleric acid (2-MVA) 6C BNL, IPCE-RAS, Chooz-II 2-ethylhexanoic acid (EHA) 8C Bicron, Palo Verdo 3, 5, 5-trimethylhexanoic acid (TMHA) 9C MPIK

9. Preparation of Gd-CBX 1.Direct synthesis (Bicron, Palo Verdo, Chooz-II) 1) HA + NH 4 OH → NH 4 A + H 2 O 2) 3NH 4 A + GdCl 3 → GdA 3 + 3NH 4 Cl 2. Liquid-liquid extraction (BNL, MPIK) Organic phase Water phase

10. Gd carboxylate complexes synthesized  Gd complexes with 2-ethylhexanoic acid (EHA) white powder  Gd complexes with 3, 5, 5-trimethylhexanoic acid (TMHA) white powder Composition of the complexes Gd-L3 L = EHA, TMHA Measured by Elemental Analysis, Vario EI, Elementar Analysensysteme GmbH

11.  Gd(TMHA) 3 can be directly dissolved in LAB  Gd(EHA) 3 only can be dissolved in the mixtures of trimethylbenzene and LAB( or trimethylbenzene and dodecane) Four Gd-LS samples have been prepared Gd (g/L)Ligand fluors solvents 1.5 TMHA PPO5g/L bis-MSB 10mg/L LAB 2.0 TMHA PPO5g/L bis-MSB 10mg/L LAB 1.5 EHA PPO5g/L bis-MSB 10mg/L V mesitylene :V LAB =2:8 2.0 EHA PPO5g/L bis-MSB 10mg/L V mesitylene :V LAB =2:8

12. Characteristics of Gd-LS Based on Gd-EHA, TMHA Pgeneral TU-1901 UV-Vis spectrophotometer 10 cm Quartz Sample Cuvettes 1 、 Absorption Measurements

13. A is the absorption at 430 nm Absorption Spectrum measured by TU-1901

14. 2 、 Attenuation Length Measurements by Vertical LED System  Vertical LED System needs larger volume of sample Vertical LED System: 1L UV-Vis spectrophotometer: 40mL  Vertical LED System can obtain more accurate attenuation Length data than ordinary UV-Vis spectrophotometer.

15. sample name Absorption MeasurementVertical LED System Abs @ 430nm Calculated Attenuation Length/m Attenuation Length/m LAB (unpurified ) 0.0053 ±0.0002 8.2±0.3 8.7±0.6 LAB (filtered) 0.0054 ±0.0003 8.0 ±0.4 9.0±1.0 LAB+PPO +bis-MSB (filtered) 0.0062 ±0.0001 7.0±0.1 7.1±0.4 Comparison of two methods for measuring Attenuation Length of the same Liquid samples

16. 3 、 Stability Test: 2g/L Gd-LS as a Function of Time

17. 4 、 Light Yield Measurements Gd (g/L) LigandfluorssolventsRelative Light Yield --PPO5g/L, bis-MSB 10mg/LV mesitylene :V Dodecane =2:80.459 --PPO5g/L, bis-MSB 10mg/LLAB0.542 1.5EHAPPO5g/L, bis-MSB 10mg/LV mesitylene :V LAB =2:80.538 2.0EHAPPO5g/L, bis-MSB 10mg/LV mesitylene :V LAB =2:80.528 1.5TMHAPPO5g/L, bis-MSB 10mg/LLAB0.492 2.0TMHAPPO5g/L, bis-MSB 10mg/LLAB0.478 relative light yield data = liquid scintillator / anthracene

18. 5 、 Emission Spectrum measurement

20. Ongoing and Future R&D at IHEP  Continue our long-term stability tests for periods more than 1 year  Study the chemical compatibility of these Gd-LS with the materials that will be used to construct the detector vessel  Develop methods to remove radioactive impurities (  10 -10 g/g)  Mass producition

21. Thank You!