# Presentation: 860616

**Brookhaven Science Associates****U.S. Department of Energy**

**Studies of Gd-LS in the U.S.A.**

**Richard L. Hahn**
***Solar Neutrino/Nuclear Chemistry Group ***
***	******	******  ******(Z. Chang, M. Yeh, A. Garnov, C. Musikas)***
***BNL Chemistry Department***

**March 15, 2004**

- Low-Energy
- Antineutrino Workshop
- Cal Poly, S.L.O.

**Brookhaven Science Associates****U.S. Department of Energy**

**A Bit of History**

*** *****This R&D begun a few years ago at BNL for LENS project, in ****	****collaboration with R. S. Raghavan and others.**
** ****Purpose: To synthesize metal-loaded liquid scintillator, M-LS, at ****	****relatively high concentration of M, 5-10% wt/wt.**
** ****M serves as target for neutrino capture (CC interaction) to excited state  ****	****in daughter nucleus, producing e****- ****+ ********ray(s) in coincidence.**
** ****Low-energy Q-value makes M suitable to detect solar ****7****Be, pp, pep,   ****	****CNO neutrinos.**
** ****Studied M = Yb(3+) and In(3+).**
** ****Approach is to prepare metal-organic complex that is stable and **
**	****soluble in LS.**

**Brookhaven Science Associates****U.S. Department of Energy**

**A Bit of History - Continued**

** ****Organic complexing agents were ****carboxylic acids, RCOOH,**** and ****	****organophosphorus compounds, such as TBP, TBPO, TOPO.**
** ****Need  * Long-term chemical stability (no precipitates or gels).**
**	****  ***** Optical clarity, i.e., long attenuation length.**
**	****  ***** High light production.**
** ****Succeeded in preparing M-LS, mainly with In,**** that satisfied our ****	****needs. ****Use (6-carbon) carboxylic acid – methylvaleric, HMVA.**
** ****In principle, this method should work well with Gd(3+) to make Gd-LS ****	****for reactor antineutrino experiment.**
** ****Began Gd R&D several weeks ago. **
** ****Have preliminary results that are very promising.**

## Systems Tested for the BNL Gd-LS Synthesis

| System* | Form of Gd  | Extractant | Notes+ |
| --- | --- | --- | --- |
| BNLGd#1 | GdCl3.6H2O
Dissolved in | Ethanol   (+ PC) | GdCl3 ethanol soln. mixed with PC. Not stable.  Product: Gd=0.39%, L@430nm=434 cm, and S=36.9% |
| BNLGd#2
 | GdCl3 .6H2O Dissolved in | Propanol (+ PC) | GdCl3 propanol soln. mixed with PC. Not stable. Product: Gd=0.10%, L@430nm=434 cm and S=57.0% |
| BNLGd#3 | Gd(MVA)xCly similar to 
In-LS | PC | Get Precipitate in the Aqueous phase. Extractn. pH=3.89. Gd-LS Stable, but Low Extractn. Efficiency.             Product: Gd=0.28%, L@430nm=167 cm, and S=58.7% |
| BNLGd#4 | Gd(MVA)2.7
Cl0.3-x OHx (TOPO)0.3
 | TOPO      (+ PC) | Aqueous and PC phases are clear. Extractn. pH=6.63. Gd-LS Stable. High Extractn. Efficiency. Product: Gd=3.24%, L@430nm=543 cm, and S=68.9% |

******* 1,2,4-trimethylbenzene (pseudocumene, PC) is used as the solvent for all the systems.**
**+** **L = attenuation length; S = Light Output relative to 100% PC.**

## Purification of HMVA by Distillation 

##  Purification of Pseudocumene, PC

## Purification of Phenyl Cyclohexane, PCH

**Brookhaven Science Associates****U.S. Department of Energy**

**Steps in ****Solvent-Extraction ****Synthesis**** ****of BNLGd#4**

**  ****Prepare Aqueous Phase.**** Neutralize  HMVA + H****2****O with NH****4****OH solution.   Product is NH****4****MVA. **
** ****Purify NH****4****MVA.**
** ****Add Organic Phase, PC + TOPO, ****to the purified Aqueous NH****4****MVA   solution.**
** ****Purify Aqueous GdCl****3 ****separately.**
** ****Solvent Extraction.**** Add GdCl****3**** solution drop-wise into the two-phase     NH****4****MVA + PC + TOPO system. White plume forms in the Aqueous Phase, disappears gradually as the Gd-MVA complex extracts into the Organic Phase. Two clear phases form at equilibrium. pH~6.**** **
** ****H****2****O Removal.**** Separate the Organic Phase and centrifuge it to remove any residual H****2****O (or pass through drying column).**
_** **_

## The Chemical Composition of BNLGd#4

|  | Gd | MVA | Cl1 | H2O | TOPO | PC2 |
| --- | --- | --- | --- | --- | --- | --- |
| wt.% | 3.24 | 6.39 | 0.23 | 0.22 | 1.90 | 88.07 |
| Number per Gd | 1 | 2.69 | 0.33 | 0.59 | 0.24 | 35.56 |

- _Analytical formula of Gd is estimated as_:
**Gd(MVA)**** 2.7****Cl****0.3-x****OH****x****(TOPO)****0.3**

- 1 **Chlorine content is estimated from the charge balance of the Gd molecule.**
**2****  PC% is estimated from the percentage of other components.**

## UV Spectra of BNLGd#4 Samples

## Attenuation of BNLGd#4 Samples

## Light Yields of the BNLGd#4 Samples

## Gd-LS From Different Labs

| Lab | Solvent | Extractant | Fluors |
| --- | --- | --- | --- |
| BNL | 1,2,4-trimethylbenzene
(PC) | Tri-n-octylphosphine oxide | 0.3 g/L BPO,
15 mg/L bis-MSB |
| Univ. Of Sheffield | -hydroxytoluene | Tri-ethylphosphate | 2-(4-Biphenyl)-5-phenyl-1,3,4-oxadiazole, 
(2-(1-Naphthyl)-5-phenyloxazole) |
| CHOOZ | IPB | Hexanol | p-PTP,
Bis-MSB |
| Eljen Technol. | Anthracene | Unknown | 3 g/L PPO,
0.3 g/L POPOP |

## Development of a gadolinium-loaded liquid scintillator for solar neutrino detection and neutron measurements. 

**(Submitted to NIM A)**
- 		_P.K. Lightfoot_, V.A. Kudryavtsev and N.J.C. Spooner
- Department of Physics and Astronomy, _University of Sheffield_, Hicks Building,
- Hounsfield Road, Sheffield, S3 7RH, UK
- I.Liubarsky
- Imperial College of Science, Technology and Medicine, London, SW7 2BW, UK
- R. Luscher and N.J.T. Smith
- Rutherford Appleton Laboratory, Didcot, Oxfordshire, OX11 0QX, UK

- Parallel Independent R&D in the U.K.

## Properties of Gadolinium-loaded 

**	********-hydroxytoluene based scintillators.**
** **

- (University of Sheffield data)

## Long term stability of 10% gadolinium loaded -hydroxytoluene 			based liquid scintillator.

- 			(University of Sheffield data)

## Comparison of the Attenuation Length(EJT and Chooz values taken from their publications) 

## Comparison of the Light Output (EJT and Chooz values taken from their publications)

**Brookhaven Science Associates****U.S. Department of Energy**

**Ongoing and Future R&D at BNL**

** ****Vary Synthesis Parameters, e.g., pH, Gd/MVA ratio.**
** ****Improve Purification Procedures.**
** ****Replace PC with Other LS Solvents, such as PCH.**
** ****Quality Control of Long-term Stability: Chemical, Optical, Light ****	****Output; Temperature-dependency (“rate approximately ****	****doubles per increase ****	****of 10****o ****C”). **
** ****Long-Pathlength Optical**** ****Measurements.**

## UV Attenuation Change with Time (In-LS)

## Light Yield Change with Time (In-LS)

## S2 – Signal from Sample

** **

- S3 – Chopper reduces UV background  S3  (S1-S2)
- S1 – a reference beam for S2  (S1-S2)

**BNL Long-Pathlength Optical system**

**Brookhaven Science Associates****U.S. Department of Energy**

**END**