1 Detection Methods at Reactor Neutrino Experiments Jun Cao Institute of High Energy Physics (Beijing) Feb. 11-15, 2013
Feb 25, 2016
Detection Methods at Reactor Neutrino Experiments
Jun Cao Institute of High Energy Physics (Beijing)
Feb. 11-15, 2013
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A better title: Liquid Scintillator Detector for High Precision (Reactor) Neutrino Studies.
Reactor neutrino experiments Towards a high precision measurement Highlighted technologies Future reactor neutrino detector Summary
Outline
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Daya Bay, Double Chooz, RENO DYBII
Reactor Neutrino Experiments
Reactor anti-neutrino experiments have played a critical role in the 60-year-long history of neutrinos.
The first neutrino observation in 1956 by Reines and Cowan.
Determination of the upper limit of mixing angle 13 in 90's (Chooz, Palo Verde)
The first observation of reactor anti-neutrino disappearance at KamLAND in 2002.
Measurement of the smallest mixing angle 13 at Daya Bay and other experiments in 2012.
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Reactor Neutrinos Most commercial reactors are PWR or BWR.
235U, 239Pu, 241Pu beta spectra measured at ILL, 238U theoretically. In LS: Energy 1-10 MeV, Rate : ~ 1 event/day/ton/GW @ 1km
Power fluctuation <1%, rate and shape precision 2-3% Rate and spectra were verified by Bugey, Bugey3, Bugey4 Reactor anomaly
Peak at 4 MeV
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Non-proliferation Monitoring
Bowden, LLNL, 2008
Non-proliferation monitoring studies supported by IAEA (France, US, Russia, Japan, Brazil, Italy)
Ton-level detector, very close to core. Water-based liquid scintillator for safety?
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The Cowan-Reines Reaction
The first observation of neutrinos in 1956 by Reines & Cowan. Inverse beta decay in CdCl3 water solution coincidence of prompt
and delayed signal Liquid scintillator + PMTs Underground
Modern experiments are still quite similar, except Loading Gd into liquid scintillator Larger, better detector Deeper underground, better shielding
e nep 2e e
Capture on H, or Gd, Cd, etc.Delayed signal
Prompt signal
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keV Scattering Experiments Neutrino magnetic moments exp.
Texono, GEMMA (HPGe) MUNU (TPC)
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CHOOZ
Baseline 1.05 km 1997-1998, France 8.5 GWth300 mwe5 ton 0.1% Gd-LSBad Gd-LS
Parameter Relative error
Reaction cross section 1.9 %
Number of protons 0.8 %
Detection efficiency 1.5 %
Reactor power 0.7 %
Energy released per fission 0.6 %
Combined 2.7 %
R=1.012.8%(stat) 2.7%(syst), sin2213<0.17
Eur. Phys. J. C27, 331 (2003)
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Palo Verde
1998-1999, US11.6 GWthSegmented detector12 ton 0.1% Gd-LSShallow overburden32 mwe
Baseline 890m & 750m
R=1.012.4%(stat) 5.3%(syst)
Palo Verde Gd-LSChooz Gd-LS 1st year 12%, 2nd year 3%
60%/year
Phys.Rev.D64, 112001(2001)
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KamLAND
2002-, Japan53 reactors, 80 GWth1000 ton LS2700 mweRadioactivity fiducial cut,
Energy threshold
Baseline 180 km
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Measuring 13
1 13 13
13 13
23 23
23 23
2 12
12 12
1 0 00 00
0 00 c s0 s c 0
c s 0s c 00 0 1
c 0 s0 0s 0 c 1
i
iiU eee
23 ~ 45Atmospheric Accelerator
12 ~ 34SolarReactor
013 = ?Reactor
Accelerator
Fogli et al., hep-ph/0506307
sin2213~0.04
Precision Measurement at reactors
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Precision Measurement at Reactors
Parameter Error Near-farReactor ν flux 1.9 % 0
Energy released per fission 0.6 % 0Reactor power 0.7 % ~0.1%
Number of protons 0.8 % < 0.3%Detection efficiency 1.5 % 0.2~0.6%CHOOZ Combined 2.7 % < 0.6%
Major sources of uncertainties:
Reactor related ~2% Detector related ~2% Background 1~3%
Lessons from past experience: CHOOZ: Good Gd-LS Palo Verde: Better shielding KamLAND: No fiducial cut
Near-far relative measurementMikaelyan and Sinev, hep-ex/9908047
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The Daya Bay Experiment• 6 reactor cores, 17.4 GWth • Relative measurement
– 2 near sites, 1 far site• Multiple detector modules• Good cosmic shielding
– 250 m.w.e @ near sites– 860 m.w.e @ far site
• Redundancy
3km tunnel
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Daya Bay Results
2011-8-15
2011-11-5
2011-12-24
Mar.8, 2012, with 55 day datasin2213=0.0920.016(stat)0.005(sys
t)5.2 σ for non-zero θ13
Jun.4, 2012, with 139 day datasin2213=0.0890.010(stat)0.005(sys
t)7.7 σ for non-zero θ13
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Double ChoozDaya Bay
Double Chooz
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Double Chooz Results
Far detector starts data taking at the beginning of 2011 First results in Nov. 2011 based on 85.6 days of data
Updated results on Jun.4, 2012, based on 228 days of data sin2213=0.0860.041(Stat)0.030(Syst), 1.7σ for non-zero θ13
sin2213=0.1090.030(Stat)0.025(Syst), 2.9σ for non-zero θ13
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RENO6 cores16.5 GW
16t, 450 MWE
16t, 120 MWE
Daya BayRENO
Double Chooz
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RENO
Data taking started on Aug. 11, 2011 First physics results based on 228 days data taking (up to
Mar. 25, 2012) released on April 3, 2012, revised on April 8, 2012:
sin2213=0.1130.013(Stat)0.019(Syst), 4. 9σ for non-zero θ13
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Rate and Spectrum
R = 0.944 ± 0.007 (stat) ± 0.003 (syst)
sin22θ13=0.089±0.010(stat)±0.005(syst)
Chinese Physics C, Vol. 37, No. 1 (2013) 011001
EH1 140 000 events EH2 66 000 eventsEH3 30 000 events
Still dominated by statistics
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Global Picture of 13 MeasurementsTi
me
line
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Detecting Reactor Antineutrino
e nep 2e e
Delayed signal, Capture on H (2.2 MeV) or Gd (8 MeV), ~30s
Prompt signal Peak at ~4 MeV
Capture on H
Capture on Gd
Inverse beta decay
Energy selection, time correlationMajor backgrounds: Cosmogenic neutron/isotopes
8He/9Li fast neutron
Ambient radioactivity accidental coincidence
0.1% Gd by weight
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Detector Design Water Shield radioactivity and
cosmogenic neutron Cherekov detector for muon
RPC or Plastic scintillatormuon veto
Three-zone neutrino detectorTarget: Gd-loaded LS
8-20 t for neutrino-catcher: normal LS
20-30 t for energy containmentBuffer shielding: oil
40-90 t for shielding
( ton ) DYB DC RENOTarget 20 8.3 16
-catcher
20 18 28
Buffer 37 88 65Total 77 114 110
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Detector Design Water Shield radioactivity and
cosmogenic neutron Cherekov detector for muon
RPC or Plastic scintillatormuon veto
Three-zone neutrino detectorTarget: Gd-loaded LS
8-20 t for neutrino-catcher: normal LS
20-30 t for energy containmentBuffer shielding: oil
40-90 t for shielding
Daya Bay Reflective panelsReduce PMT numbers to 1/2
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Gadolinium-doped Liquid Scintillator
nH, 2.2 MeV nGd, 8.05 MeV
Coincidence pair in (1-200) s
e nep 2e e
Delayed signal, Capture on H (2.2 MeV) or Gd (8 MeV), ~30s
Prompt signal
Significantly Lower the low-background requirement
Well-defined target mass(no fiducial volume cut)
KamLAND didn't dope; DYB-II will not dope.
w/o doping, DYB 20 t detector 5m, 110 t --> 6.5m, 210 t; lower eff. due to muon veto; larger uncer.
Singles Spectrum
Natural Radioactivity
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Inner Gd-LS: precise target mass, E higher than radioact. Middle layer: -catcher to contain gamma energy
attenuation length of 1 MeV ~ 20 cm neutron selection eff increase from 0.2% to 0.4% for 2-layer Energy resolution is NOT sensitive (7% 12%)
Outer layer: shield radioactivity, uniform response. Uncertainty from accidental backgrounds (DYB) ~0.05%
Why 3-layer
w/ -catcher w/o -catcher
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Idea of "identical detectors" throughout the procedures of
design / fabrication / assembly / filling. For example: Inner Acrylic Vessel, designed D=31205 mm
Variation of D by geometry survey=1.7mm, Var. of volume: 0.17% Target mass var. by load cell measurement during filling: 0.19%
Functional Identical Detectors
Diameter IAV1 IAV2 IAV3 IAV4 IAV5 IAV6Surveyed(mm
)3123.12 3121.71 3121.77 3119.65 3125.11 3121.56
Variation (mm)
1.3 2.0 2.3 1.8 1.5 2.3 "Same batch" of liquid scintillator
5x40 t Gd-LS, circulated
200 t LS, circulated4-m AV in pairs Assembly in pairs
20 t filling tank
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Side-by-side Comparison (1) Relative uncertainties: difference between detectors
nGd 8 MeV peak
Energy scale of 6 ADs
Two ADs in EH1
within 0.5%
n capture time AD spectra
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Designed detector uncertainties (relative)
Daya Bay 0.15-0.38%, Double Chooz 0.5%, RENO 0.5% Comparing to 2.7% of CHOOZ
Achieved 0.2% in short term
The State-of-the-art Neutrino Detector
Can be improved w/ det. by det. correction
Can be further constrained w/ more data
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Side-by-side Comparison (2)
Expected ratio of neutrino events: R(AD1/AD2) = 0.982 The ratio is not 1 because of target mass, baseline, etc.
Measured ratio: 0.987 0.004(stat.) 0.003(syst.)
This check shows that syst. are under control, and will eventually "measure" the total syst. error
Neutrino Enery spectraData set: 2011.9 to 2012.5
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Doping metal into organic LS is not easy.
Previous Gd-LS
Palo Verde Gd-LSGdCl3+EHA (carboxylic acid)
Chooz Gd-LSGd(NO3)3 + hexanol
3%/y60%/y
Solvent: Xylene, Pseudocumene, ... attack acylic (+MO) New solvents of high flash point, low toxicity ...
LAB, PXE, DIN, PCH
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Systematic studies on Gd-LS after the failure of CHOOZ.
β-diketones: Acac, DBM, BTFA, HPMBP, THD Carboxylic acid: 2-MVA(6C), n-heptanoic(7C), EHA(8C),
TMHA(9C) Organophosphorous: TOPO, D2EHP, TEP, DBBP
Stability, solubility, transparency and purification, large-scale production ...
Gd-LS
Exp. Solvent Gd Agent Quantity (t)
CHOOZ IPB Hexanol 5Palo Verde PC+MO EHA 12
Double Chooz
PXE+dodecane
-dikotonate
s
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Daya Bay LAB TMHA 185fluor: PPO, second wavelenth shifter: bis-MSB
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Gd-LS Production in DYB
Clear Gd(TMHA) in LAB~ 0.5% concentration
Fluor-LAB
4 ton MixingN2 bubbling
filtrationTo 40ton Tank
GdCl3 purification
Gd(TMHA)3
synthesis and dissolution
5x40t Gd-LS tanks
Wet solidPH tuned TMHA
GdCl3
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Radiopurification of GdCl3
Co-precipitation to remove U/Th: increase the PH of GdCl3 water solution (~5% precipitate), filter, and tune back.
Complexing to remove Ra• 232Th228Ra228Th224Ra212Bi212Po(164s)
• 238U234Th234U230Th226Ra214Bi214Po(0.3s)210Pb210Po
• 235U231Pa227Ac219Rn215Po(1.78ms)
(1s, 3s)
(10s, 160s)
(1ms, 2ms)
Total
232Th
238U
227Ac
227Ac
Delayed energy (MeV)
Prom
pt e
nerg
y (M
eV)
232Th: 10 mBq/ton (2.5e-3 ppb) 238U: 0.5 mBq/ton (4e-5 ppb)227Ac: 10 mBq/ton
Chin. Phys. C37, 011001 (2013)
Natural abundance 238U/235U ~ 22In DYB Gd-LS: 238U/235U ~ 0.05
Purification of at least 400 times (some are during refining of Gd)
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Daya Bay: weekly calibration
ACU (enable >99.7% μ eff.): LED, Ge, Co, 241Am-13C (0.5 Hz) Special ACU: Cs, Mn, Am-Be Manual (4π): Co, 238Pu-13C (4% 6 MeV gamma)
Double Chooz: laser, Cs, Ge, Co, Cf RENO: LED, Cs, Ge, Co, Cf Relative energy scale uncertainty within 0.5%
Calibration
ACU-A ACU-CACU-B
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ESR film: Specular reflection for better understanding of detector Sandwich structure, keep intact surface with vacuum pressure Electrostatic adherence to ensure a perfect specular surface.
Reflective Panels4.5 m in diameter
2 cm thick
1cm Acrylic sheet
1cm Acrylic sheet
65 m ESREpoxy sealingbulk polymerization
PMT Coverage
pe yield(pe/MeV
)
pe yield
/Coverage
Daya Bay 192 8"
~6% 163 1.77
RENO 354 10"
~15%
230 1
Double Chooz
390 10"
~16%
200 0.81
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Reflective Panel in Detector
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Next Step: Daya Bay-II Experiment
Daya Bay Daya Bay II 20 kton LS detector 3%/E̅ resolution Rich physics
Mass hierarchy Precision measurement
of 4 oscillation parameters to <1%
Supernovae neutrino Geoneutrino Sterile neutrino Atmospheric neutrinos Exotic searches
Talk by Y.F. Wang at ICFA seminar 2008...NuFact 2012; by J. Cao at Nutel 2009...NPB 2012 (ShenZhen); Paper by L. Zhan, Y.F. Wang, J. Cao, L.J. Wen, PRD78:111103,2008; PRD79:073007,2009
DYB-II has been approved in China in Feb. 2013 Equivalent to CD1 of US DOE
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The reactors and possible sites Daya Bay Huizhou Lufeng Yangjiang Taishan
Status Operational Planned Planned Under construction Under constructionPower 17.4 GW 17.4 GW 17.4 GW 17.4 GW 18.4 GW
Daya BayHuizhou Lufeng
Yangjiang
Taishan
Hong Kong
Kaipin, Jiangmeng, Guang Dong
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Detector ConceptMuon tracking
Liquid Scintillator20 kt
Acrylic sphere : φ34.5m
SS sphere : φ 37 .5m
Water Seal
~15000 20” PMTsoptical coverage: 70-80%
Stainless Steel Tank
Oil buffer 6kt
Water Buffer 10kt
VETO PMTs
1) Traditional Design (figure)• Alternate: acrylic -> ballon• Alternate: acrylic -> PET sphere
2) No SST (like SNO)3) Only SST, no inner vessel4) Modulized oil box in SST
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DYB-II Energy Resolution
, or (2.6/
DYB-II MC, based on DYB MC (p.e. tuned to data), except DYBII Geometry and 80% photocathode coverage SBA PMT: maxQE from 25% -> 35% Lower detector temperature to 4 degree (+13% light) LS attenuation length (1 m-tube measurement@430 nm)
from 15 m = absoption 24 m + Raylay scattering 40 m to 20 m = absorption 40 m + Raylay scattering 40 m
Uniformly Distributed Events
After vertex-dep. correction
R3
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Discovery Power
If m232 at 1% precision,mass
hierarchy could be determined to ~5 in 6 years. (core distribution and energy non-linearity may degrade it a little bit.
Taking into account m232 from
T2K and Nova in the future:
Contribution from absolute m2
32 measurement
Current DYB II m2
12 3% 0.6%
m223 5% 0.6%
sin212 6% 0.7%
sin223 20% N/A
sin213 14% 4% ~ 15%
Will be more precise than CKM matrix elements !
Probing the unitarity of UPMNS to ~1% level
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15000 20-in PMTs with maxQE 35% MCP-based PMT, led by IHEP, since 2008. Hamamatsu dynode PMTs (or HPD-based) LAPPDs, Borosilicate capillary array for
MCP, U. Chicago, ANL, etc. Ultra-transparent liquid scintillator
Default recipe: LAB + PPO + bis-MSB (Daya Bay undoped LS)
High transparence LAB Purification of LS
Mechanics of the giant detector Energy calibration
Technical Challenges
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DYBII: Brief schedule Civil preparation: 2013-2014 Civil construction: 2014-2017 Detector R&D: 2013-2016 Detector component production: 2016-2017 PMT production: 2016-2019 Detector assembly & installation: 2018-2019 Filling & data taking: 2020
Welcome collaborators
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S.B. Kim, talk at Neutrino 2012
• Mass Hierachy• Solar neutrino• Geoneutrino• Supernovae• T2K beam• exotic
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Summary Reactor Neutrino experiments were prosperous. Liquid scintillator + PMTs Detector uncertainties reduced from ~3% to 0.2% in
recent 13 measurements. As the most powerful man-made neutrino source,
reactor neutrinos will continue to contribute in Mass hierarchy Precision measurement of mixing parameters to < 1%
unitarity test of the mixing matrix Sterile neutrinos, Neutrino magnetic moments, ...
Challenges: Liquid scintillator, PMTs, Gaint detector
Happy New Year !
In 2013:Feb. 3 Kitchen God FestivalFeb. 10 Chinese New YearFeb. 24 The Lantern Festival