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Hahn_SLO

VIEWS: 2 PAGES: 23

									                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




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

Brookhaven Science Associates      March 15, 2004
  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- + g 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 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.
   Brookhaven Science Associates
     U.S. Department of Energy
        Systems Tested for the BNL Gd-LS Synthesis
        System*          Form of Gd      Extractant                   Notes+

       BNLGd#1           GdCl3.6H2O       Ethanol     GdCl3 ethanol soln. mixed with PC. Not
                         Dissolved in      (+ PC)     stable. Product: Gd=0.39%,
                                                      L@430nm=434 cm, and S=36.9%

       BNLGd#2           GdCl3 .6H2O     Propanol     GdCl3 propanol soln. mixed with PC. Not
                         Dissolved in     (+ PC)      stable. Product: Gd=0.10%,
                                                      L@430nm=434 cm and S=57.0%

       BNLGd#3           Gd(MVA)xCly         PC       Get Precipitate in the Aqueous phase.
                          similar to                  Extractn. pH=3.89. Gd-LS Stable, but
                            In-LS                     Low Extractn. Efficiency.
                                                      Product: Gd=0.28%, L@430nm=167 cm,
                                                      and S=58.7%
       BNLGd#4          Gd(MVA)2.7         TOPO       Aqueous and PC phases are clear.
                        Cl0.3-x OHx        (+ PC)     Extractn. pH=6.63. Gd-LS Stable. High
                        (TOPO)0.3                     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
      0.14



                 430 nm
      0.12

       0.1

      0.08                                  Higher BP

      0.06
Abs




      0.04
                                                        Lower BP fraction
      0.02
                            Original
         0

      -0.02
                          Distilled
      -0.04
           400        440             480      520      560      600        640   680   720   760   800
                                                               WL (nm)
                Purification of Pseudocumene, PC
         0.03

        0.025                                                      Alpha Aesar
                                                                   Al2O3 Column
         0.02
                                                                   Distilled

        0.015
R_Abs




         0.01

        0.005


            0

        -0.005
              350 370 390 410 430 450 470 490 510 530 550 570 590 610 630 650 670 690
                                             WL (nm )
   Purification of Phenyl Cyclohexane, PCH
          0.03


         0.025
                                                               Acros
          0.02                                                 Triple Distilled
                                                               Al2O3 Column
         0.015
R-Abs.




          0.01


         0.005


            0


         -0.005
               350 370 390 410 430 450 470 490 510 530 550 570 590 610 630 650 670 690
                                               WL (nm)
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).


    Brookhaven Science Associates
      U.S. Department of Energy
       The Chemical Composition of BNLGd#4

               Gd        MVA          Cl1         H 2O       TOPO            PC2

    wt.%       3.24       6.39        0.23        0.22        1.90           88.07

Number          1         2.69        0.33        0.59        0.24           35.56
per Gd
1Chlorine content is estimated from the charge balance of the Gd molecule.
2 PC% is estimated from the percentage of other components.




           Analytical formula of Gd is estimated as:
                 Gd(MVA) 2.7Cl0.3-xOHx(TOPO)0.3
                       UV Spectra of BNLGd#4 Samples

        0.045
                                                      Gd 3.24%, R_Abs   0.008
                                                      Gd 1.05%, R_Abs   0.006
        0.035                                         Gd 0.50%, R_Abs   0.005
                                                      Gd 0.10%, R_Abs   0.003

        0.025
R_Abs




        0.015


        0.005


        -0.005
                 350    390   430   470   510   550       590      630          670
                                          WL (nm)
                       Attenuation of BNLGd#4 Samples
              1800


              1500


              1200
Atten. (cm)




               900


               600
                                                               Gd 3.24%, L543 cm
                                                               Gd 1.05% L 724 cm
               300                                             Gd 0.50% L 869 cm
                                                               Gd 0.10% L 1448 cm

                 0
                     350   370   390   410   430   450   470    490    510    530
                                               UV (nm)
                   Light Yields of the BNLGd#4 Samples
     10000



            1000
CR (Arb.)




             100
                            PC
                            Gd 3.24%, S 68.9%
              10            Gd 1.05%, S 82.9%
                            Gd 0.50%, S 92.3%
                            Gd 0.10%, S 94.3%

               1
                   0   50     100     150       200   250    300     350   400   450
                                                 Channel
                                (fluors: 3g PBD/L, 15mg bis-MSB/L)
            Gd-LS From Different Labs

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

  Eljen       Anthracene         Unknown          3 g/L PPO,
Technol.                                        0.3 g/L POPOP
  Parallel Independent R&D in the U.K.


     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
             Properties of Gadolinium-loaded
              a-hydroxytoluene based scintillators.
  Property
                           Percentage loading of Gadolinium


                    0          2.5         5.0      7.5        10.0

 Boiling
  point            205         205        207       208        212
   (C)
  Flash
  point             93         98         103       105        109
   (C)
Light
collection,        1.13       0.78        0.58      0.46       0.34
pe/keV            0.057     0.039      0.029    0.023     0.017

Attenuatn
 length,           3010       1460      366 18   209 10     142 8
   cm              420       153


              (University of Sheffield data)
Long term stability of 10% gadolinium loaded a-hydroxytoluene
                    based liquid scintillator.
                  (University of Sheffield data)
                 Comparison of the Attenuation Length
(EJT and Chooz values taken from their publications)
                2400

                2100                                        BNLGd#4 @430 nm
                                                            UniSFD @420 nm
                1800                                        EJT_EJ331 @424 nm
                                                            Chooz @430 nm
                1500
 Attenu. (cm)




                1200

                900

                600                                                L = 742[Gd] -0.25
                300

                  0
                       0   1   2       3    4     5     6     7    8      9      10    11
                                                   Gd (%)
                                   UV Attenuation as A Function of Gd%
               Comparison of the Light Output
(EJT and Chooz values taken from their publications)
     100

     90                                                        BNLGd#4
                                                               USFD_Gd
                                                               EJT_EJ331
     80
                                                               Chooz

     70
S%




     60
                    S% = 97e-0.10[Gd]
     50

     40

     30
           0    1    2      3      4    5        6   7   8      9      10   11
                                        Gd (%)

                           Light Output as A Function of Gd%
              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 10o C”).
 Long-Pathlength Optical Measurements.


  Brookhaven Science Associates
    U.S. Department of Energy
  UV Attenuation Change with Time (In-LS)
         0.03


        0.025


         0.02                                             Beginning, 0.004
                                                          3 months, 0.006
        0.015
R_Abs




         0.01


        0.005


            0


        -0.005
              350   380   410   440   470   500   530   560   590   620      650   680

                                              WL (nm)

                                 z115 (In%=6.8, MVA%=23.1)
                      Light Yield Change with Time (In-LS)
    10000

                                                                PC
                                                                Beginning, 39.8%
           1000
                                                                3 months, 40.0%
CR (Arb)




           100



            10



             1
                  0      50   100    150    200    250    300     350     400      450
                                             Channel

                              (z155, Fluors: 3g PBD/L , 15mg bis-MSB/L)
              Photon
              Detector                               Lock-in                      S2
                                     S1
                (1)                                  Amplifier


   10-cm                 Spherical                                                     Spherical
   Herriott               Mirror                             S3                         Mirror
    cell
                                                                                                     Photon
                                                1-meter glass Herriott cell                          Detector
                                                                                                       (2)


      Mirrors


                                 Beam Chopper                                                       HV
                                                                  LASER, 452 nm                    Power
                                                                                                   Supply
                                            Density Filter
                                              O.D.=1




                  BNL Long-Pathlength Optical system
•S2 – Signal from Sample
•S3 – Chopper reduces UV background  S3  (S1-S2)
•S1 – a reference beam for S2  (S1-S2)
                                END




Brookhaven Science Associates
  U.S. Department of Energy

								
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