Brookhaven Science Associates U.S. Department of Studies of Gd-LS in the U.S.A. (and the U.K.) 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.
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Brookhaven Science Associates U.S. Department of Energy Studies of Gd-LS in the U.S.A. (and the U.K.) Richard L. Hahn Solar Neutrino/Nuclear Chemistry.
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Brookhaven Science AssociatesU.S. Department of Energy
Studies of Gd-LS in the U.S.A.(and the U.K.)
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 WorkshopCal Poly, S.L.O.
Brookhaven Science AssociatesU.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 7Be, 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 AssociatesU.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.
Brookhaven Science AssociatesU.S. Department of Energy
Steps in Solvent-Extraction Synthesis of BNLGd#4
Prepare Aqueous Phase. Neutralize HMVA + H2O with NH4OH solution. Product is NH4MVA.
Purify NH4MVA.
Add Organic Phase, PC + TOPO, to the purified Aqueous NH4MVA solution.
Purify Aqueous GdCl3 separately.
Solvent Extraction. Add GdCl3 solution drop-wise into the two-phase NH4MVA + 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.
H2O Removal. Separate the Organic Phase and centrifuge it to remove any residual H2O (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) 2.7Cl0.3-xOHx(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.