Studies of Gd-LS at BNL for Reactor Neutrino θ 13 Measurement

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1 Studies of Gd-LS at BNL for Reactor Neutrino θ 13 Measurement Minfang Yeh Brookhaven National Laboratory, Chemistry Department, Upton, NY US/UK Reactor θ 13 Workshop, Oxford, UK, June 21-22, 2004

2 BNL Neutrino/Nuclear Chemistry Group Richard Hahn Minfang Yeh Zheng Chang Alex Garnov Claude Musikas Leader, Senior Scientist Associate Scientist Research Associate Research Associate Consultant Students

3 BNL Chemistry and Neutrinos HOMESTAKE Radiochemical Detector 615 tons of C 2 Cl 4 ; 37 Cl + ν e 37 Ar + e - GALLEX Radiochemical Detector 30 tons of Ga; 71 Ga + ν e 71 Ge + e - SNO Water Cerenkov Detector 1000 metric tons of ultra-pure D 2 O LENS Real-time Radiochemical Detector (R&D) 115 In in Liquid Scintillator BNL-AGS NEUTRINO FACTORY Very Long-Baseline Experiment- Neutrino Beam from BNL

4 Absorbance/10cm Characteristics of Bell Labs-BNL In-loaded Scintillator for LENS-Sol Start A= months A= months A= l(nm) Stability: The UV-VIS absorbance (430 nm) with time over six months (BNL#115, In%=6.77) Counts PC Start 39.8% 3 months 40.0% 6 months 40.7% channel Light yield with time over six months (BNL#115, 3g PBD/L, 15mg bis-msb/l) BL/BNL developed a very consistent In-LS chemical synthesis method for LENS. This In-LS has: high In content (~7%) good light yield (~40% of PC) long attenuation length (L(1/e) ~9 m without shifter) chemical stability for over 6 months since synthesis (top figures). The BNL dual-beam, 1-meter optical measurement using blue laser (442nm) confirmed the result from 10-cm UV spectrometer (bottom figure).

5 Overview of Gd-LS Needs of Gd-LS long attenuation length good light yield long-term stability Synthesis of Gd-LS ph complexing agent equilibrium time purification of chemicals

6 Purification of HMVA by Distillation nm 0.08 Higher BP Fractionion Abs Lower BP fraction Original Distilled l (nm)

7 Purification of Pseudocumene, PC Alpha Aesar Al2O3 Column Distilled Abs l (nm)

8 Purification of Phenyl Cyclohexane, PCH Acros Triple Distilled Al2O3 Column Abs l (nm)

9 Gd-LS Synthesis and Characterization Chemical Analysis (Org.) (Aqu.) 1,2,4-Trimethylbenzene (PC) Gd-LS Gd(RCOO) 3 Gd 3+ (Cl - ) 3 + 3RCOO - Gd(RCOO) 3 NH 3 + RCOOH NH 4+ + RCOO - Filtration/Separation L 1/e by UV-Vis and blue laser. Light Yield (S%) [Gd 3+ ] by colorimetric method [RCOOH] total by acid-base titration [RCOOH] free by IR [Gd species] PC by IR [H 2 O] by Karl-Fischer titrator [Cl - ] by electrochem

10 Preliminary Preliminary Chemical Composition of BNL 3.24% Gd-LS Gd(3+) MVA Cl 1 H 2 O TOPO PC 2 wt.% Number/Gd Chlorine 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 in LS: Gd(MVA) 2.7 Cl 0.3-x OH x (TOPO) 0.3

11 Infrared 1760 cm cm -1

12 [HMVA] free Estimation HMVA=0. 3M HMVA=0. 5M 1710 cm Calibration Curve 0. 8 HMVA=0. 7M HMVA=0. 9M 1 Abs HMVA=1. 5M HMVA=2. 2M Abs y = 14.96x + 3E-05 R 2 = [HMVA] cm Wavenumber (cm -1 )

13 Chemical Species from IR BNL65 after vacuum distillation BNL65 before vacuum distillation In(OH) cm Wavenumber (cm -1 )

14 UV Spectra of BNL Gd-LS Samples Gd 3.24%, R_Abs Gd 1.05%, R_Abs Gd 0.50%, R_Abs Gd 0.10%, R_Abs Abs l (nm)

15 Attenuation Length from UV-Vis L = log( e) L A( L) L is attenuation length L is path length = 10 cm at BNL A(L) is absolute absorption at 430 nm L = (0.434 * 10 cm)/(0.008) = 542 cm = 5.4 m

16 Attenuation Lengths of BNLGd-LS 1800 Samples Atten. (cm) Gd 3.24%, L543 cm Gd 1.05% L 724 cm Gd 0.50% L 869 cm Gd 0.10% L 1448 cm l (nm)

17 Dual-beam long-path Optic System Photo- Detector S1 Lock-in Amplifier S2 10-cm Herriott cell Spherical Mirror S3 Spherical Mirror 1-meter glass Herriott cell Photo- Detector Mirrors S2 Signal from Sample Beam Chopper Density Filter O.D.=1 50 mw, Blue LASER, 442 nm For In-LS, 1-m laser measurement confirmed the extrapolation from 10-cm UV results. S3 Chopper reduces UV background S3 (S1-S2) S1 Reference beam for S2 (S1-S2) HV Power Supply

18 Light Yields of the BNLGd-LS Samples Counts PC Gd 3.24%, S 68.9% Gd 1.05%, S 82.9% Gd 0.50%, S 92.3% Gd 0.10%, S 94.3% Channel (fluors: 3g PBD/L, 15mg bis-msb/l)

19 BNL BNL can produce high quality, Gd-LS sample with good light yield and appropriate attenuation length with adjustable Gd wt% up to ~8%, but so do others, such as Bicron

20 UV Attenuation of BNL Gd-LS Samples vs Commercials BNL_3.24%, BNL_1.05%, BNL_0.50%, BNL_0.10%, BC525_0.5% BC521_1%, Abs l (nm)

21 Light Yield of BNL Gd-LS Samples vs Commercials Counts BNL_1.05%, 82.9% BNL_0.50%, 92% BC521_1%, 85% BC525_0.5%, 81% PC_03/03/ Channel

22 Stability Test: UV Attenuation of BNL Gd-LS after 2 months BNL_1.05%, BNL_0.50%, BNL_0.10%, Abs BNL Gd-LS 2 months before BNL_1.05% BNL_0.50% BNL_0.10% l (nm)

23 Laser Electron Accelerator Facility

24 Preliminary Preliminary Counts 1.0E E+05 Decay Constant of Gd-LS Fluorensence of BC E l (nm) V LEAF of BC521 (8 MeV, 50ps/Pulse) ns (Gd %) w W-Shifters t d (ns) BNL 1.0 PBD/bis-MSB 3.64 BC Yes; N/A 2.81

25 Preliminary Preliminary BNL vs BC-521 BNL Gd-LS Measured by BNL BNL BC-521 Bicron Gd % 1% 1% 1% Attenuation Length (m) > 400 Light Yield (s%) 82.9% PC 85.0% PC 57.0% anthracene Stability 2 months N/A long term Decay Constant (ns)

26 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 D10 o C ). Long-Pathlength Optical Measurements.