Water-based Liquid Scintillator - Department of Physics

Water-based Liquid Scintillator 

Minfang Yeh 

Brookhaven National 

Laboratory, Chemistry-555, 

Upton, NY11973 

ANT-2010, Santa Fe, NM 

Research sponsored by the U.S. Department of Energy, Office of Nuclear Physics and 

Office of High Energy Physics, under contract with Brookhaven National Laboratory – 

Brookhaven Science Associates.

First anti-neutrino detector 

PET or CAT scan? 

http://www.strokecenter.org/patients/diagnosis/ct.htm

BNL 40+ years of neutrino at chemistry 

1961 

Radiochemical 

Water 

Liquid 

Scintillator 

• HOMESTAKE Radiochemical Detector 

615 tons of C 2 Cl 4 ; 

37 

Cl + e 37 Ar + e - (~40 years) 

• GALLEX Radiochemical Detector 

30 tons of Ga; 71 Ga + e 71 Ge + e - (1986 - 1998) 

• SNO Water Čerenkov Detector (SNOLab) 

1-k tons of ultra-pure D 2 O (1996 - 2006) 

• LENS Real-time LS Detector (R&D) 

100 tons of ~8% 115 In in Liquid id Scintillator ill (began ~2000) 

• LBNE Long-Baseline Neutrino Experimen 

V beam to DUSEL (began~2002) 

• Daya Bay High-Precision Reactor 13 Detector 

200 tons of 0.1% Gd in Liquid Scintillator (began ~2003) 

• SNO+ Neutrino-less Double Beta Decay Real-time Detector 

1-k tons of 0.1% Nd in Liquid Scintillator (began ~2005) 

 

 

• 

 

 

2009 

• Neutrino Application 

• Nonproliferation and/or Reactor Monitoring 

• Li/Zr/Ca-loaded Liquid Scintillator (began 2008) 

• Water-based Liquid Scintillator 

3 

M. Yeh for ANT-2010

Liquid scintillators for large-scale physics 

• Expertise in low background counting, organic scintillators and, in particular 

metal loaded organic scintillators. 

• Interest for neutrino and neutron detectors. 

• Laboratory developed for the investigation of optical characteristics of a large variety of liquid 

scintillators: 

• PC, PCH, DIN, PXE, LAB 

• with high light yield, long attenuation length and low flammability 

• Absorption and emission spectra, extinction length, dependence on purity level, 

concentration of fluors and wavelength shifters, environmental factors (e.g. temperature, 

humidity, exposure to air) 

• Capability of purifying and synthesizing materials in-house and of 

controlling the chemical processes. 

• Collaboration between Physics and Chemistry Depts. at BNL 

44 

M. Yeh for ANT‐2010

Metal loaded liquid scintillators 

Development and production of Metal-loaded loaded (Yb, In, Nd, Zr, Gd, Li, etc) liquid 

scintillator (LS) for neutrino experiments 

• LENS uses 125 tons of In-loaded LAB or PC beginning of M-LS in 2000 

• Daya-Bay uses 200 tons of Gd-loaded LAB 

• SNO+ uses 1 KT of Nd-loaded LAB 

• M. Yeh et al. Gadolinium-Loaded Liquid Scintillator for 

High-Precision Measurements of Antineutrino 

Oscillations and the Mixing Angle, θ13, NIM A 578 

(2007) 329-339 

Study of optical properties as a function of purity levels and of metal concentration 

Self-scavenging method to 

remove Th/U and improve UV 

carboxylic acids are the preferred choice 

5 

M. Yeh for ANT‐2010 

• M. Yeh et al. Purification i of lanthanides for large 

neutrino detectors, NIM A 618 (2010) 124–130

Liquid Scintillator for Particle Detector 

• High efficiency of converting kinetic 

energy of charged particle to detectable 

light 

• Good light transparency to the emission 

wavelength 

• Short decay time for fast signal pulse 

• Mass-producible 

• Index of refraction for scattering light 

• High flash point, low toxicity, safe to be 

used in confined space 

• Long stability and chemical compatibility 

6 


Liquid Scintillation (versus Water Cherenkov) 

Cons 

Safety: Chemical hazard, 

Fire hazard, and Reactivity 

Cost: 

$2k/ton or $100M for 50 KT 

Handling & ES&H 

event reconstruction and 

PID 

Pros 

orders of magnitudes light 

output: smaller detector or 

less photo-sensors 

Physics of charged particles 

below Cherenkov threshold 

Excellent PSD to suppress 

background events 

Sub-MeV (geo-, solar- and 

reactor) neutrinos 

7 


Comparisons of Selected Liquid Scintillators 

first identified by SNO+ 

8 


NEPA assessment of fire safety for ongoing 

and newly yproposed p experiments 

Experiment 

LS 

Borexino PC ~3 

NEPA 

450 

Rating 400 

350 

Flashing 

Point 

Boiling 

Point 

9 

LENS LAB/PC 1/3 

Daya Bay LAB 1 

SNO+ LAB 1 

Reno LAB 1 

Double- 

CHOOZ 

KamLAND 

NOvA 

LENA 

20%PXE + 

80%dodecane 

20% PC + 

80%dodecane 

5% PC + 95% 

MO 

PXE/LAB/dodec 

ane 

Temperaturem m, C 

300 

250 

200 

2~1 

150 

3~2 

1~2 

1/1/2 

Liquid scintillators used in all ongoing g or proposed p experiments are 

combustible ; some are even close to flammable 

M. Yeh for ANT‐2010 

100 

50 

0 

PC PCH DIN PXE LAB MO Dodecane 

Scintillator

A large (>50kT) liquid scintillator has 

challenges of 

• cost 

• attenuation 

• ES&H 

• Compatibility 

• etc 

IS THERE AN ALTERNATE? 

10

Light Yield of PC% in dodecane 

• By 137 Cs Compton 

scattering 

• Light-yield is a 

function of 

percents of liquid 

scintillator; but is 

not linear 

11 


Water Optical Transmission 

• Superior attenuation 

length of water 

could compensate 

the loss of photon 

• High proton density 

(6.69 69 atoms per c.c.) 

12 


Goal of Water based liquid scintillator 

Water-based liquid scintillator is different from dissolving 

wavelength shifter in water. 

Develop a W-LS to be used as energy spectrometers in large-scale 

physics experiments 

• Replace the hundreds to many tons of unloaded or metalloaded 

organic liquid scintillators to provide: 

• simpler sensitive detection medium 

• fewer compatibility problems 

• cost savings 

• Non-linear photon production plus superior water attenuation 

length makes it possible to detect physics below Cherenkov 

threshold 

• PDK + channel becomes accessible 

13 


Nucleon Decay 

The SUSY SU(5) model predicts 

the K-decay mode to be 

dominant with a partial 

lifetime varying from 10 29 y to 

10 35 yrs ! 

( p k 

v) 

 

2.310 

33 

yrs 

SK 

H.Ejiri Phys. Re ev. C48 (1993) 14 442 

• 22.5 kT (7.5 x 10 33 protons & 6.0 x 

10 33 neutrons) at 40% coverage 

• T K+ ~340 MeV/c: below Cerenkov 

threshold 

• 

16 

O (p → 15 3/2 ) N* + 63 6.3 MeV 

14 


Water-based LS for PDK + 

• A 50-kt detector would have a sensitivity of t >4×10 34 

yrs for PDK + model after 10 years of run time (LENA) 

• 150 p.e./MeV (30%) 

• 1/e ~20m 

• >4000m 

• 9000 photons/MeV for 100% LAB 

• 25% coverage gives 180 p.e. per MeV (DYB) 

• Assuming W-LS has 20% of S of LAB, 

• ~5 = exp(/20); 1/e >32m 

• Need to catch kaon before decay: t d

• Polarity Tension 

• Like to like 

CAN WE LOAD IT?

Surfactant reduces the tension; thus 

balances the “like to like” 

Conventional watermiscible 

cocktails for 

/ counting or in 

medical imaging are 

not stable in water 

A highly stable W-LS 

with long 

attenuation length 

that generates light 

as particle detector 

17 


As much as 40% of liquid scintillator 

can be loaded d in water 

18 


• P urification of raw mat erials before 

production 

• Online- purification during the data- 

taking period 

LONG ATTENUATION LENGTH 

IS THE KEY 

M. Yeh for ANT‐ 19 

2010

Purification Scheme and Strategy 

• dry-column extraction 

ti 

• freezing-isolation 

• Short-path vacuum distillation 

• Aqueous/organic solvent-washing 

• Re-crystallization/dissolution 

• contractors 

20 


0.5% W-LS achieved excellent optical 

transmission 

i 

after a rather complicated 

purification scheme 

21 


Online purification is achievable; but 

not easy 

22 


Characterization of W-LS by GC-MS 

23 


• -ray Compton Scattering 

• Emission fluorescence spectroscopy 

IS THERE A LIGHT? 

M. Yeh for ANT‐ 24 

2010

~7% W-LS has a light-yield of 15~20% 

of pure LAB (by 137 Cs) 

UV 

—W‐LS — 

LAB 

25 


Emissions of W-LS and pure LS 

• s of 10% W-LS is 

~25% of pure LAB 

• Non-radiative 

energy-transfer 

mechanism is 

not wellunderstood 

yet 

26 


SNO went through h a search of water-soluble 

wavelength shifters and identified few 

promising candidates (for Cerenkov) 

27 

M. Yeh for ANT-2010

• Time-resolved fluorescence 

spectroscopy 

• Single-photon counting? 

HOW FAST IS THE LIGHT?

decay time is in the region of interest 

29 


• Attenuation measurement of light 

change at 1% precision 

• Use for Daya Bay, SNO+ and LENS 

BNL 2-M DUAL-BEAM SYSTEM

Purification is essential for optical transmission, 

particularly for large LS detector 

Close to the baseline 

that a long path- 

length system is 

needed! 

31 


BNL 2-m system 

- at 1% precision 

-2 s per measurement 

32 


0.1% Nd-LAB by UV 10-cm and 2-m system 

2.42m 

3.75m 

3.31m 

5.26m 

6.23m 

Chris 33 Ouellet M. et Yeh al. for in preparation ANT‐2010 for NIM‐A

Double-baselinedbaselined 

10-cm UV agrees 

with 2-m 

measurement very 

well! 

Johnny Goett et al. in preparation for 

NIM‐A 

34 


Summary 

• W-LS could be a promising detection medium 

for large detector 

• Samples of W-LS have been stable (1-yr+) since 

preparation 

• Plenty of light; but need to optimize fluor selection 

(organic or aqueous) 

• The decay time is fast 

• Online purification is the key; but can we run it at 

lower temperature to minimize the 

microorganisms? 

i • Physics of PDK + and sub-MeV neutrinos 

35 


Future Plan 

• Light production property, quenching effect 

as a function of dE/dx, in response to a proton 

beam at NSRL (BNL) with kinetic energy of 100 

to 1000 MeV. 

• A 250-L prototype for Cf-252 neutron capture. 

• Can we preserve the scintillation and 

Cerenkov radiations simultaneously? 

• Little scintillation not to overcome Cerenkov (5 

p.e./MeV at 30%) 

• Neutron-tagging g by adding metal (such as 

Gd) into the W-LS? 

• IBD followed by Gd-capture sum of 8-MeV 

36 

M. Yeh for ANT-2010

Neutrino at BNL-Chemistry 

• Richard Hahn 

• James Cumming (retiree) 

Postdoctoral 

Students/Technicians 

• Sunej Hans 

• Richard Rosero 

• Liangming Hu • Wanda Beriguete 

• Pankaj Sinha • Wai Ting Chan 

• 1~2 openings • John Goett (LNGS) 

Research sponsored by the US U.S. Department of Energy, Office of Nuclear Physics and Office of High 

Energy Physics, under contract with Brookhaven National Laboratory – Brookhaven Science Associates. 

37 M. Yeh for ANT‐2010

Water-based Liquid Scintillator - Department of Physics

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