BNL Neutrino/Nuclear Chemistry Group Updates of BNL Gd-LS BNL Neutrino/Nuclear Chemistry Group Richard Hahn Leader, Senior Scientist Minfang Yeh Associate Scientist Alex Garnov Post Doc (Group reduced to 3 people. Alex will depart April 5, 2006. Starting search for his replacement.)

Attenuation Length Measurements 1- and 10- cm cells in Shimadzu UV-1601 spectrometer (200 – 1100 nm) 1-m horizontal cell, blue laser system (442 nm) 1.5-m vertical pathlength, LED variable wavelength system (350 – 700 nm, working with M. Diwan of BNL Physics) under room light under black light

Gd-LS Attenuation Stability (10 cm cells) You should probably comment that the Braidwood collaboration had decided to use 0.2% Gd, to increase the signal and shorten the capture time to ~15 microsec. (1) Someone may ask why the absorbance depends (a) on the Gd concentration, and (b) on the ratio of PC to dodecane. (2) You should remind them how the Abs. Value is related to the Attenuation Length; e.g., 0.004  10 meters. Abs = 0.004 ~ Atten. Length = 10 m

Scintillator Selection Gd Loading d (g/cm3) UV Abs.430 before/after Purif. Method n20 Light Yield H atoms‡ per c.c Flash Point PC Yes 0.889 0.008/0.002 Vacuum Distil. 1.504 1 5.351022 48 C PCH 0.95 0.072/0.001 Column 1.526 0.46 4.281022 99 C DIN 0.96 0.040/0.023 0.87 3.271022 >140 C PXE Yes, but not stable 0.985 0.044/0.022 3.381022 167 C LAB 0.86 0.001/0.000 1.482 0.98 2.521022 130 C Mineral Oil No 0.85 0.002 ~0.001 N/A ~1.46 ~ 1.62 –1.65 1022 215 C Dodecane No (<20%) 0.75 0.001 ~0.000 1.422 3.181022 71 C Explain “be/af”. Are these the Abs values before and after the purification? ‡calculated from density.

New Candidate for 13 Experiment LAB (Linear Alkyl Benzene) containing side alkyl chains of 10-13 C atoms; average ~11.3 atoms. Long attenuation length, low cost, low reactivity, high flash point, and high light yield  An ideal scintillator, discovered from our collaborative SNO+/++, that can also be used in 13 experiment. Boiling Point (oC) 275 - 307 Melting Point (oC) < -50 Flash Point (oC) 130 Vapor Pressure (mmHg) < 0.1 mmHg @ 20oC Vapor Density (Air =1) 8.1 Solubility in Water Insoluble Molecular Weight 233 – 237 g/mol pH Not applicable Viscosity 5 – 10 cps @ 20oC Evaporation Rate (water =1)

LAB Purification

Light Yield of LAB versus PC 3 g/L PBD + 15 mg/L bis-MSB

Optical Spectrum of 0.2% Gd in 20%PC-80%LAB Fact: 20%PC-80% LAB mixture is stable for ~ 1.5 month since synthesis. Question: Can we load Gd directly into LAB? Answer: Yes!

Optical Comparisons of ~1% Gd in LAB and PC 430 nm BNL has successfully loaded Gd into 100% LAB Gd-LAB has much better transparency at < 400 nm and at least ~50% improved optical transparency at 430 nm, compared to Gd-PC

~1% Gd in LAB and PC 430 nm Gd-LAB has much better transparency at < 400 nm and ~20% better optical at 430 nm, compared to Gd-PC

h Funding Constraints of the BNL Group: Personnel costs This EOI was requested by OHEP. My group’s base program comes from DOE/ONP. We took a major hit in FY-06. Currently are barely able to support our existing 3-person group. It is not at all clear if ONP will give any support for reactor theta-13 work. We are starting to write our new FWP, due in early February for FY-2007-2009. I plan to talk with ONP (Gene Henry) in the next week; also with OHEP to get their input about this issue. Brookhaven Science Associates U.S. Department of Energy h

h Funding Constraints of the BNL Group: Personnel costs, II We are involved in other neutrino R&D, re solar neutrinos and double beta-decay. Our major thrust is on Metal-loaded LS, with current main emphasis on Gd-LS for theta-13. Other efforts: (a) Compatibility of M-LS with acrylic and other structural materials. (b) Radioactive contaminants, assay and control. Basic Questions: Will ONP continue to fund our “base program” with supplementary support for theta-13 from OHEP? Or, will ONP share theta-13 costs with OHEP? Or Horrors! Will ONP cut us significantly? Brookhaven Science Associates U.S. Department of Energy h

h Funding Constraints of the BNL Group: Personnel costs, III In summary, there is a likely chance that we will not receive ONP funding for postdocs to work on Theta-13. What to do? Should we ask OHEP for this support? Basic annual total cost of a postdoc at BNL is $100 K (includes all overhead costs). Our bare minimum need is one new postdoc; two are preferable. Brookhaven Science Associates U.S. Department of Energy h

h Funding Constraints of the BNL Group: “Materials”costs, I Let’s not lose sight of the fact that the Gd-LS tests that we have been doing at BNL involve small Amounts, <1 L batches. Clearly we want to scale this up to several L, or even more. I am not comfortable basing all of our claims about the quality of the Gd-LS on small samples, especially since our full-scale detector modules will contain 65 tons each. Might we be fooling ourselves? Costs for chemicals, materials, and equipment specifically for Gd-LS: Our request in our 2004 proposal was very modest, $28 K. Brookhaven Science Associates U.S. Department of Energy h

h Funding Constraints of the BNL Group: “Materials”costs, II Is that sufficient for our R&D? We are building new Systems at BNL, e.g., to scale up our Gd-LS production to tens of liters per batch, to measure optical transparency of large volumes,… A major question is: do Braidwood people want appreciable amounts of Gd-LS, to do tests independent of the BNL Group, to get data to validate Monte Carlos,… So far, the only request I have is from Ed, for ~10 L for his small-scale prototype at Chicago. Is that all? The cost to a large extent depends on your needs. What shall we do? Brookhaven Science Associates U.S. Department of Energy h