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 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 GdExtractantNotes + BNLGd#1 GdCl 3.6H 2 O Dissolved in Ethanol (+ PC) GdCl 3 ethanol soln. mixed with PC. Not stable. Product: Gd=0.39%, cm, and S=36.9% BNLGd#2 GdCl 3.6H 2 O Dissolved in Propanol (+ PC) GdCl 3 propanol soln. mixed with PC. Not stable. Product: Gd=0.10%, cm and S=57.0% BNLGd#3 Gd(MVA) x Cl y similar to In-LS PCGet Precipitate in the Aqueous phase. Extractn. pH=3.89. Gd-LS Stable, but Low Extractn. Efficiency. Product: Gd=0.28%, cm, and S=58.7% BNLGd#4 Gd(MVA) 2.7 Cl 0.3-x OH x (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%, 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 GdMVACl 1 H2OH2OTOPOPC 2 wt.% Number per Gd Analytical formula of Gd is estimated as: Gd(MVA) 2.7 Cl 0.3-x OH x (TOPO) 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 LabSolventExtractantFluors 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 Unknown3 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. Property Percentage loading of Gadolinium Boiling point (  C) Flash point (  C) Light collection, pe/keV 1.13      Attenuatn length, cm 3010      8 (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)

1-meter glass Herriott cell LASER, 452 nm HV Power Supply Photon Detector (1) Photon Detector (2) Density Filter O.D.=1 Mirrors Beam Chopper Spherical Mirror Lock-in Amplifier 10-cm Herriott cell S1 S2 S3 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