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.

Purification of HMVA by Distillation

-0.04

-0.02

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

400 440 480 520 560 600 640 680 720 760 800

WL (nm)

Ab

s

43

0 n

m

Dis tilled

Original

Lower BP fraction

Higher BP

Purification of Pseudocumene, PC

-0.005

0

0.005

0.01

0.015

0.02

0.025

0.03

350 370 390 410 430 450 470 490 510 530 550 570 590 610 630 650 670 690

WL (nm)

R_A

bs

Alpha Aesar

Al2O3 Column

Distilled

Purification of Phenyl Cyclohexane, PCH

-0.005

0

0.005

0.01

0.015

0.02

0.025

0.03

350 370 390 410 430 450 470 490 510 530 550 570 590 610 630 650 670 690

WL (nm)

R-A

bs.

Acros

Triple Distilled

Al2O3 Column

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.

UV Spectra of BNLGd#4 Samples

-0.005

0.005

0.015

0.025

0.035

0.045

350 390 430 470 510 550 590 630 670

WL (nm)

R_

Ab

s

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

Attenuation of BNLGd#4 Samples

0

300

600

900

1200

1500

1800

350 370 390 410 430 450 470 490 510 530

UV (nm)

Att

en

. (c

m)

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

Light Yields of the BNLGd#4 Samples

(fluors: 3g PBD/L, 15mg bis-MSB/L)

1

10

100

1000

10000

0 50 100 150 200 250 300 350 400 450

Channel

CR

(A

rb.)

PCGd 3.24%, S 68.9%Gd 1.05%, S 82.9%Gd 0.50%, S 92.3%Gd 0.10%, S 94.3%

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. SpoonerDepartment of Physics and Astronomy, University of Sheffield, Hicks Building,

Hounsfield Road, Sheffield, S3 7RH, UKI.Liubarsky

Imperial College of Science, Technology and Medicine, London, SW7 2BW, UKR. 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

0 2.5 5.0 7.5 10.0

Boiling point (C)

 

205 

205 

207 

208 

212

Flash point (C)

 

93 

98 

103 

105 

109

Light collection,pe/keV

 

1.13 0.057

 

0.78 0.039

 

0.58 0.029

 

0.46 0.023

 0.34

0.017

Attenuatn length,

cm

 

3010 420

 

1460 153

 

366 18

 

209 10

 

142 8

 

(University of Sheffield data)

Long term stability of 10% gadolinium loaded -hydroxytoluene based liquid scintillator.(University of Sheffield data)

0.2

0.22

0.24

0.26

0.28

0.3

0.32

0.34

0.36

0.38

0.4

16/4/02 31/5/02 15/7/02 29/8/02 13/10/02 27/11/02 11/1/03

date

light

yie

ld (

pe/k

eV

)

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

UV Attenuation as A Function of Gd%

L = 742[Gd]-0.25

0

300

600

900

1200

1500

1800

2100

2400

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

Att

en

u. (

cm

)

BNLGd#4 @430 nmUniSFD @420 nmEJT_EJ331 @424 nmChooz @430 nm

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

Light Output as A Function of Gd%

S% = 97e-0.10[Gd]

30

40

50

60

70

80

90

100

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

S%

BNLGd#4USFD_Gd

EJT_EJ331Chooz

Brookhaven Science AssociatesU.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 10o C”).

Long-Pathlength Optical Measurements.

UV Attenuation Change with Time (In-LS)

z115 (In%=6.8, MVA%=23.1)

-0.005

0

0.005

0.01

0.015

0.02

0.025

0.03

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

WL (nm)

R_A

bs

Beginning, 0.004

3 months, 0.006

Light Yield Change with Time (In-LS)

(z155, Fluors: 3g PBD/L , 15mg bis-MSB/L)

1

10

100

1000

10000

0 50 100 150 200 250 300 350 400 450

Channel

CR

(Arb

)

PC

Beginning, 39.8%

3 months, 40.0%

1-meter glass Herriott cell

LASER, 452 nmHV

PowerSupply

PhotonDetector

(1)

PhotonDetector

(2)

Density Filter O.D.=1

Mirrors

Beam Chopper

Spherical Mirror

Spherical Mirror

 

Lock-inAmplifier

10-cmHerriott 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 AssociatesU.S. Department of Energy

END