Update of Gd-LS R&D at IHEP

Ding Yayun, Zhang Zhiyong, Cao Jun

Institute of High Energy Physics,

Chinese Academy of Sciences

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

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

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

C6H5-C12H25

Further study about the composition of LAB is ongoing.

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

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

P OR

R

R

P

O

RR

R

P

RR

R

Ln3+

O

Gd3+

-Diketone

Acetylacetone (Acac) Chooz-II

Low solubility in the scintillator solvent

HC OC

R

R' CO

CH

O

CR R'

C

O

CH

OC R

R'

CO

Ln3+

_

_

_

Gd3+

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

Preparation of Gd-CBX

1. Direct synthesis (Bicron, Palo Verdo, Chooz-II)

1) HA + NH4OH → NH4A + H2O

2) 3NH4A + GdCl3 → GdA3 + 3NH4Cl

2. Liquid-liquid extraction (BNL, MPIK)

Organic phase

Water phase

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, TMHAMeasured by Elemental Analysis,

Vario EI, Elementar Analysensysteme GmbH

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/LLAB

2.0 TMHA PPO5g/L

bis-MSB 10mg/LLAB

1.5 EHA PPO5g/L

bis-MSB 10mg/LVmesitylene:VLAB=2:8

2.0 EHA PPO5g/L

bis-MSB 10mg/LVmesitylene:VLAB=2:8

Characteristics of Gd-LS Based on Gd-EHA, TMHA

Pgeneral TU-1901 UV-Vis spectrophotometer

10 cm Quartz Sample Cuvettes

1 、 Absorption Measurements

A is the absorption at 430 nm

Absorption Spectrum measured by TU-1901

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.

sample name

Absorption Measurement Vertical LED System

Abs

@ 430nm

Calculated Attenuation Length/m

Attenuation Length/m

LAB

(unpurified )

0.0053

±0.00028.2±0.3 8.7±0.6

LAB

(filtered)

0.0054

±0.00038.0 ±0.4 9.0±1.0

LAB+PPO

+bis-MSB

(filtered)

0.0062

±0.00017.0±0.1 7.1±0.4

Comparison of two methods for measuring Attenuation Length of the same Liquid samples

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

4 、 Light Yield Measurements

Gd (g/L)

Ligand fluors solvents Relative Light Yield

- - PPO5g/L, bis-MSB 10mg/L Vmesitylene:VDodecane=2:8 0.459

- - PPO5g/L, bis-MSB 10mg/L LAB 0.542

1.5 EHA PPO5g/L, bis-MSB 10mg/L Vmesitylene:VLAB=2:8 0.538

2.0 EHA PPO5g/L, bis-MSB 10mg/L Vmesitylene:VLAB=2:8 0.528

1.5 TMHA PPO5g/L, bis-MSB 10mg/L LAB 0.492

2.0 TMHA PPO5g/L, bis-MSB 10mg/L LAB 0.478

relative light yield data = liquid scintillator / anthracene

5 、 Emission Spectrum measurement

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 (10-10g/g)

Mass producition

Thank You!Thank You!