WbLS measurements at BNL David Jaffe 1 BNL 20140516 1 cohort: L.J.Bignell, D.Beznosko, M.V.Diwan, S.Hans, S.Kettell, R.Rosero, H.Themann, B.Viren, E.Worcester, M.Yeh, C.Zhang 1 / 16
Light production in water, LS & WbLS 1. ˇ Cerenkov (point source 2 , directional, prompt) 1.1 Light yield is calculable: N ≈ ( path length ) × N 0 (sin 2 θ C ) 1 1 1.2 Spectrum LY ( λ ) ∝ λ 2 1 − β 2 n ( λ ) 2 2. Scintillation (point source, isotropic, extended in time) 2.1 Light yield proportional to energy deposit, modulo quenching. Must be measured. 2.2 Narrow spectrum 3. Absorption & re-emission (possibly diffuse source, isotropic, extended in time) 3.1 Optical γ from ˇ Cerenkov or scintillation can be absorbed & re-emitted by medium 3.2 Has potential to shift ˇ C γ from VUV to visible to a typical photodetector (eg. bialkalai PMT) LY for these processes is comparable for ≤ 10% concentration WbLS. Disentangling them and understanding the details of λ -dependence is tedious. 2 As opposed to diffuse source 2 / 16
λ -dependence (arbitrary norm. except absorption length) 100 WbLSEAbsorptionELengthEl1/mmQ CerenkovEEmissionESpectrumyE475EMeVEProtons 10 WbLSEEmission PhotomultiplierEQuantumEEfficiency 1 CerenkovEEmissionESpectrumyE2EGeVEProtons 0.1 0.01 0.001 0.0001 0.00001 150 200 250 300 350 400 450 500 550 600 650 Wavelength (nm) 3 / 16
Measurements at BNL The following pages have details of two sets of measurements in a low energy proton beam. 1. NSRL 3 run 12C: Light yield measured for water, LS, 0.4% and 1% WbLS, investigate quenching. Result: LY approximately linear with LS concentration 2. NSRL run 13A: Absolutely calibrate 1% WbLS LY against ˇ Cerenkov LY Result: LY of 1% WbLS is ≈ 110 optical photons / MeV ( ± 10% uncertainty) Goals: 1. Determine increase in sensitivity of a SK-like detector with WbLS to p → K + ¯ ν . 2. Disentangle competing light production processes. 3 NASA Space Radiation Laboratory at BNL, of course. 4 / 16
Early MC estimate of p → K + ¯ ν sensitivity with 1%-WbLS-based detector Projected Sensitivity 35 10 Lifetime Sensitivity (90% C.L.) + p " ! + K WbLS 22.5 kt 34 10 Super-K 33 10 1995 2000 2005 2010 2015 2020 2025 2030 2035 2040 Year τ ( p → K + ¯ ν ) > 2 × 10 34 y at 90% C.L. in 10 years 10 5 / 16
NSRL12C Beam setup (identical liquids in each tub) Not to scale Reflectivity>95% Reflectivity<10% PTFE tub “T1” Al tub “T2” A2 15cm 15cm A1 Proton H1 H2 H3 beam VC 0.635cm 0.635cm H1,H2,H3 plastic scint. hodoscope 2cmX2cmX0.5cm Trigger: H1•H2 T1,T2 Hamamatsu R7723 2”PMTs CAEN V1729A FADC 12bit,1GSPS NSRL beam monitor: A1•A2 A1 (A2) is 1cm 2 (2 cm 2 ), 2mm thick plastic scint. 6 / 16
NSRL12C: PTFE tub with PMT 7 / 16
NSRL12C: Incident and deposited energies (MeV) Incident Incident Energy Beam β energy deposited energy T1 T2 T1 T2 T1 T2 Sample 210 0.57 0.45 202 113 70 113 Water, WbLS 210 0.57 0.47 202 124 59 124 LS 475 0.75 0.72 470 421 39 42 Water, WbLS 475 0.75 0.73 470 427 34 36 LS 2000 0.95 0.95 1996 1962 28 28 Water, WbLS 2000 0.95 0.95 1996 1966 24 24 LS ◮ p → K + ¯ ν : β K = 0 . 57 ⇒ T p = 210 MeV ◮ T p = 475 MeV is just above proton ˇ Cerenkov threshold ◮ T p = 2000 MeV ≈ minimum-ionizing (max NSRL beam energy) ◮ Calculated incident velocities, incident and deposited energies in MeV for “T1” (PTFE tub) and “T2” (Aluminum tub) using NIST’s proton stopping power and range tables (PSTAR). Estimated uncertainty is a few MeV. 8 / 16
12C results: LY vs deposited energy T1_Charge(PE)/Edep(MeV) vs Edep(MeV) T2_Charge(PE)/Edep(MeV) vs Edep(MeV) T1_Charge(PE)/Edep(MeV) T2_Charge(PE)/Edep(MeV) 2 10 10 10 1 1 -1 10 -1 10 water -2 10 wbls1 -2 10 wbls1 wbls2 wbls2 ls ls 20 30 40 50 60 70 20 40 60 80 100 120 140 Edep(MeV) Edep(MeV) White PTFE tub. Black PTFE-coated Al tub. PE/MeV vs MeV deposited. PE/MeV vs MeV deposited. 9 / 16
12C results: Normalized PE/MeV vs LS concentration Normed PE/MeV vs LS-concentration(%) [Water at 0.001% for plot] 1. LY approximately proportional to Normed PE/MeV 1 concentration for 210, 475 MeV. 2. 2000 MeV shows effect of -1 10 ˇ Cerenkov contribution -2 10 -3 10 475 T1 2000 T1 T2 210 T2 475 T2 2000 -3 -2 -1 2 10 10 10 1 10 10 LS-concentration(%) [Water at 0.001% for plot] PE/MeV (normalized to LS PE/MeV) vs LS concentration for proton beam data. 10 / 16
Table of results Ratio(%) to 100% concentration Conc 210 MeV 475 MeV 2000 MeV (%) T1 T2 T1 T2 T1 T2 0. — — 0 . 07 ± 0 . 02 — 1 . 89 ± 0 . 21 — 0.4 — 0 . 19 ± 0 . 02 0 . 29 ± 0 . 02 0 . 32 ± 0 . 02 1 . 95 ± 0 . 20 2 . 18 ± 0 . 24 1.0 — 1 . 22 ± 0 . 08 0 . 82 ± 0 . 05 1 . 32 ± 0 . 08 2 . 16 ± 0 . 20 3 . 57 ± 0 . 40 100 — 100 ± 10 . 80 100 ± 6 . 79 100 ± 10 . 68 100 ± 10 . 22 100 ± 10 . 64 1. T1 (white PTFE) 210 MeV LS inaccurate: PMT saturated 2. T2 (black PTFE) water data unreliable: PMT re-positioned 3. 2000 MeV data complicated by ˇ Cerenkov contribution 11 / 16
Compare NSRL12C and Compton-edge data Normed Light Yield vs concentration(%) [Water at 0.001% for plot] Normed Light Yield 1 Compare relative light yield of proton beam data with preliminary -1 10 Compton-edge data for WbLS and LAB in cyclohexane(CX). 1. In WbLS, light yield is -2 10 proportional to concentration. 2. In cyclohexane, light yield is higher at low concentrations. -3 10 T1 475 Normed PE/MeV vs LS-concentration(%) [Water at 0.001% for plot] T1 2000 Normed PE/MeV vs LS-concentration(%) [Water at 0.001% for plot] T2 210 Normed PE/MeV vs LS-concentration(%) [Water at 0.001% for plot] T2 475 Normed PE/MeV vs LS-concentration(%) [Water at 0.001% for plot] T2 2000 Normed PE/MeV vs LS-concentration(%) [Water at 0.001% for plot] Normalized LY vs LAB concentration in CX Normalized LY vs LAB concentration in WbLS -3 -2 -1 2 10 10 10 1 10 10 concentration(%) [Water at 0.001% for plot] 12 / 16
NSRL13A setup schematic $ ./01,*'2,31..,'456 1. External 2 × 2 cm 2 plastic scintillator hodoscopes define beam into yellow region. 2. Dimensions selected so that ˇ C ring from incident proton fully illuminates downstream PMT. 3. Liquids: water and 1% WbLS 4. Beam energies: 475 and 2000 MeV 5. Detector can be rotated by 180 ◦ for systematics control. 6. Detector is black ABS plastic, reflectivity < 10% 13 / 16
NSRL13A expected and actual results Beam Expected Actual (in photo-electrons) Energy PMT PMT PMTA PMTB PMTB PMTA (MeV) 4 Liquid DS US DS US DS US 2000 Water N C 0 42.2 0.9 40.4 1.4 2000 1%-WbLS Q C + Q s Q s 27.9 9.5 27.7 8.1 475 Water 0 0 1.4 1.1 1.3 1.0 475 1%-WbLS 6.4 5.5 6.6 5.6 N s N s Uncertainties: ± 10% for > 2PE, ± 20% otherwise. Q C = N C × (1 − P a ) and Q s = N s + N C P a P r where P a ∼ absorption prob. and P r ∼ re-emission probability. Illustrative only, neglects λ -dependence of production, absorption, re-emission, transmission and detection efficiency. Complications: 1. 475 MeV is not below proton ˇ C threshold (Doh!) 2. δ − ray production 3. Non-zero reflectivity 4 Deposited energies: ∼ 37 and ∼ 26 . 3 MeV for 475 and 2000 MeV, resp. 14 / 16
NSRL13A interpretation of results 1. A full Geant4-based simulation has been developed and applied for the NSRL13A data. 2. Combining results and taking into account the calculated energy loss in the liquid, the scintillator light yield is 113( ± 10%) optical photons per MeV deposited. 3. To first order, P a = 1 − N WbLS − N WbLS DS US ≈ 46% , N Water DS in other words, approximately half of the photons in ˇ Cerenkov ring will be eliminated in the 1% WbLS . Normalized Counts 0.14 0.12 Comparison of simulation(hist) and 0.1 data(points) for 475 MeV protons in 0.08 0.06 1%-WbLS 0.04 0.02 0 0 5 10 15 20 25 30 35 40 Charge Collected (Number of Photoelectrons) 15 / 16
Next steps 1. Unified analysis of NSRL12C and NSRL13A data with full Geant4-based simulation. 2. Measurement of decay-time distributions in NSRL12C, NSRL13A data 3. Measurement and simulation of WbLS attenuation length in 2 meter system 4. Re-examination of p → K + ¯ ν sensitivity 5. Deployment of “1-ton-prototype”, a 995 mm ID, 1250 mm internal height, 25.4 mm thick UVT acrylic vessel, for measurements with cosmics 16 / 16
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