Water-based Liquid Scintillator and Isotope Loadings Minfang Yeh Neutrino and Nuclear Chemistry, Brookhaven National Laboratory Future Solar Neutrino Detector at JinPing
Water-based Liquid Scintillator 12000 Optical Photons per MeV LAB in cyclohexane A cost-effective, new liquid medium 10000 utilizing nonlinear light-yield as a function 8000 of scintillator % and superior optical 6000 property of water for physics below 4000 Cerenkov or low-energy neutrino detection 2000 20%LS give ~50% light as a pure LS Cherenkov transition 0 0 50 100 overlaps with scintillator energy-transfers will • be absorbed and re-emitted to give isotropic LS% light. emits at >400nm will propagate through the • electrons detector (directionality). PID using timing cut and energy LSND rejects neutrons by a reconstruction to separate the directional factor of 100 at ¼ Cherenkov & ¾ Scintillation light (NIM Cherenkov (fast) and isotropic A388, 149, 1997). scintillation (slow, controllable) Environmentally and chemically friendly neutrons 6/17/2014 Minfang Yeh, BNL 2
Cherenkov & Scintillation Separation Cherenkov is ~5% of scintillation in conventional scintillators Difficult to reconstruct • directionality At 1%WbLS, Cherenkov: scintillation is ~1:1 Slow scintillator vs. prompt • Cherenkov Cherenkov and Scintillation separation could discriminate low-energy , e - , e + and More background suppression, larger detector fiducial volume 6/17/2014 Minfang Yeh, BNL 3
Two types of WbLS 180 160 Mean Absorption Length (m) 140 Cerenkov (e.g. SK, SNO) 120 100 Water-based Liquid Scintillator 80 Water-like Oil-like • >70%H2O • A new loading 60 • Cherenkov + technology for Scintillation hydrophilic 40 • Cost-effective elements 20 Scintillator (e.g. SNO+, Daya Bay) 0 100 1000 10000 Photon/MeV Minfang Yeh, BNL 6/17/2014 4
Liquid Scintillator Development Facility • A unique facility (since 2002) for Radiochemical, Cerenkov, and Scintillator (water ‐ based and metal ‐ doped) detectors for particle physics experiments. • Expertise trained and facility established over years of operations. • $1M facility including XRF, LC ‐ MS, GC ‐ MS, TFVD, FTIR, UV, Fluorescence emission, light ‐ yield coinc. PMT, 2 ‐ m system, low bkg. counting, etc. (access to ICP ‐ MS at SBU) for detector R&Ds and prototype tests. 6/17/2014 Minfang Yeh, BNL 5
WbLS Cherenkov & Scintillation Detection • Proton decay remains to be one of the top challenges A simulated event with 90 scintillation photons/MeV in a SK detector for p → k � v � • An order of magnitude improvement over the current SK sensitivity (2.3 10 33 yrs) • μ + 15 Number of PE 0 p → K + + ν μ + + ν μ _ e + + ν μ + ν e 10 12 ns 0 2.2 μ s μ + e + e + 50 K + 10 10 2 10 3 10 4 Hit Time (Time of Flight Corrected) [ns] 6/17/2014 Minfang Yeh, BNL 6
1% WbLS-2012 (Proof-of-Concept) • Started R&D since 2009 • A clean liquid (at 450nm and above); Good Attenuation Length need 10 4 optical purification • A fast pulse • can load as much as 35% of LS in H 2 O • Investigate light propagation below and above Cerenkov • proton beams & sources Fast Timing 6/17/2014 Minfang Yeh, BNL 7
Proton-beam Measurements at BNL WbLS Detectors • Two NSRL runs from 2012-2013 • Same sample; different geometries NSRL @BNL • Cherenkov at higher energy and scintillation below Č threshold 2 Detectors 3 low Intensity Proton Beams 4 Material Samples PTFE Water pure water 210 MeV dE/dx ~ K+ from PDK Tub 1 (highly reflective WbLS 1 0.4% LS white Teflon) 475 MeV Cerenkov threshold WbLS 2 0.99% LS Aluminum coated Tub 2 with black Teflon 2 GeV MIP LS pure LS 6/17/2014 Minfang Yeh, BNL 8
Scintillation below Cherenkov threshold • Cherenkov dominates at 2GeV while scintillation takes over at 475MeV and below • Principals of detection below Cherenkov threshold are proven LS response is divided by 30 10 T1 (white Teflon) Charge (in PE/MeV) Ratio to LS at 475-MeV 10 9 Water Sample WbLS1 Sample 8 T1 Data 1 WbLS2 Sample 7 T2 Data LS Sample /30 Sample/LS Ratio Charge (PE/MeV) 6 * 0.1 5 4 3 0.01 2 linear or nonlinear? 1 0.001 0 0.1 1 10 100 100 1000 10000 LS Concentration (%) Beam Energy (MeV) Minfang Yeh, BNL 6/17/2014 9
WbLS Isotope loading Metal-loaded LS for Neutrino Physics Reactor Solar Others 6/17/2014 Minfang Yeh, BNL 10
Examples of Metal-doped WbLS • Conventional loading method using organic Conventional loading is no good for hydrophilic ions (i.e. Te) complexing ligands has been successfully applied to reactor �̅ � detection (e.g. Gd-LS) • –OH group is a known quencher • difficult for hydrophilic elements • WbLS adds a new dimension of metal-loading Lithium-doped scintillator detector Neutron Tagging • Solar neutrino ( 7 Li, 92.5% abundance) • Reactor antineutrino ( 6 Li, 7.6% abundance) Tellurium-doped scintillator detector • Double-beta decay isotope ( 130 Te, 34% abundance) Future ton-scale 0 ββ • 8-MeV ’s (Gd) vs. ,T ( 6 Li) Lead-doped scintillator calorimeter • Solar neutrino • Total-absorption radiation detector 6/17/2014 Minfang Yeh, BNL 11
Solar Neutrino Targets 115 In + e 115 Sn + e - + ( τ =4.76 µs) 2 γ (LENS) • High nature abundance at 95.7% • Low Q value at 114-keV, sensitive to >95% pp continuum Triple coincidence allows tagging of e event • • 6-8% loading with conventional organometallic technology 208 Pb + e 208 Bi* + e - & 208 Pb + x 208 Pb* + x (HALO) • Abundance at 52.4% • Bursts of neutrons via CC and NC • Neutron detection by IBD reaction using scintillator ( 208 Pb is a double magic nuclei) • Targeting 10% nat Pb using WbLS (aligned with medical applications) 7 Li + e 7 Be + e - • group state (E thresh = 0.861 MeV) and first excited state (E thresh = 1.339 MeV) • High abundance at 92.5% • Conventional organometallic loading is not stable (e.g. Bugey-3) • 1~3% loading using WbLS (aligned with short-baseline reactor experiments) Few others: 11 B, 35 Cl, 31 P,…, etc. 6/17/2014 Minfang Yeh, BNL 12
Li-loading by WbLS 4000 0.1% Li - 2nd formulation 3500 0.1% Li Commercial Product 3000 Counts (AU) LAB + PPO + MSB BNL + Yale • A Li-doped (0.1-0.5%) LS that has been stable 2500 over 1.5 years (light-yield and optical better 2000 than commercial product) for PROSPECT 1500 1000 • Background investigations at three different reactor sites 500 • Start full-scale (~10 tons) at Near Site in 2015 0 • Improve PSD as demonstrated by Gd-LS; 0 1000 applicable to Li-LS ADC Channel • Continue R&D for higher loading at >1% A stable 0.1% Li-LS at ~5000 ph/MeV 0.05 51213 71913 0.04 90813 103113 0.03 Absorbance 0.02 0.01 PROSPECT Daya Bay 0 200 700 PSD enhancement for 0.1% Gd-doped LS (compatible with plastics) over 6 months; and further improvement can be achieved Wavelength (nm) 6/17/2014 Minfang Yeh, BNL 13
How practical is a large water Cherenkov scintillation detector? “the U.S. to host a large water Cherenkov neutrino detector, as one of three additional high-priority activities, to complement the LBNF liquid argon detector, unifying the global long-baseline neutrino community to take full advantage of the world’s highest intensity neutrino beam. The placement of the water and liquid argon detectors would be optimized for complementarity. This approach would be an excellent example of global cooperation and planning ” – P5 (scenario C) First WbLS-LBNF workshop was held at LBNL in June: http://underground.physics. berkeley.edu/WbLS/slides/ A group study to explore potential physics by WbLS BNL, LBNL/U. Berkeley, U. Penn., UC Davis, U. Chicago, U. Princeton, • UCLA, U. Hawaii A technical or white paper is under discussion • Regular phone calls and R&D proposals are planned International workshop? 6/17/2014 Minfang Yeh, BNL 14
1% WbLS-2014 • Water-like WbLS (e.g. WATCHMAN) The WbLS-2012 needs 10 4 optical • 0.1 purification WbLS-2014 (extinction coefficient) 0.09 • relying on the vendor for a cleaner starting WbLS-2012 SK-water material 0.08 • Multi-step technologies proven; but high Absorption Length (1/m) cost and labor-consuming WbLS non-purified 0.07 • The WbLS-2014 • New chemical components 0.06 • Non-purified and includes scattering; need to measure its effect 0.05 • extinction coefficients calculated from each component (successfully predict LS) 0.04 total = organic + water • organic ~ water ~ 0.0046 (m -1 ) at 430nm • 0.03 • Region of 300-400nm dominated by flour/shifter; need to be optimized 0.02 0.01 0 200 300 400 500 600 Wavelength (nm) optical improvement after one-pass 6/17/2014 Minfang Yeh, BNL 15
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