the daya bay reactor neutrino experiment r. d. mckeown caltech on behalf of the daya bay...
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The Daya Bay Reactor Neutrino Experiment
R. D. McKeown
CaltechOn Behalf of the Daya Bay Collaboration
CIPANP 2009
Maki – Nakagawa – Sakata Matrix
Gateway toCP Violation!
CP violation
3
e Survival Probability
• “Clean” measurements of , m2
• No CP violation• Negligible matter effects
Dominant 12 Oscillation
Subdominant 13 Oscillation
• 4 reactor cores, 11.6 GW• 2 more cores in 2011, 5.8 GW • Mountains provide overburden to shield cosmic-ray
backgrounds• Baseline ~2km• Multiple detectors → measure ratio
Daya Bay Nuclear Power Plant
Daya Bay NPP
Location
55 km
Total Tunnel length ~ 3000 m
Experiment Layout
• Multiple detectorsper site cross-check detector efficiency
• Two near sites sample flux from reactor groups
20T
Antineutrino Detector
SS Tank
AcrylicVessels
20 T Gd-doped liquid scintillator
192 8” PMT’s
Calibration units
Gamma catcher
Buffer oil
• 3 zone design• Uniform response• No position cut • 12%/√ E resolution
e +p → e+ + n
n capture on Gd (30 s delay)
Muon Veto System
WaterCerenkov(2 layers)
Redundant veto system → 99.5% efficient muon rejection
RPC’s
Gd-Liquid Scintillator Test Production
500L fluor-LAB
Two 1000L 0.5% Gd-LAB
5000L 0.1% Gd-LS
0.1% Gd-LS in 5000L tank
Daya Bay experiment uses 200 ton 0.1% gadolinium-loaded liquid scintillator (Gd-LS). Gd-TMHA + LAB + 3g/L PPO + 15mg/L bis-MSB
4-ton test batch production in April 2009.
Gd-LS will be produced in multiple batches but mixed in reservoir on-site,
to ensure identical detectors.
Gd-LS stability in prototype
time (days)
Ab
sorp
tion
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Controlling Systematic Uncertainties
sin2213
MeasuredRatio of
Rates
+ flow & mass measurement
DetectorEfficiency
Ratio
0.2% Storage
Tank
FarNear
Proton Number Ratio
0.3%
Calibration systems
Target Mass Measurementfilling platform
with clean roomISO Gd-LS weighing tank
pump stations
detector
load cell accuracy < 0.02%
Coriolis mass flowmeters
< 0.1%
20-ton, teflon-lined ISO tank
Gd-LS MOLS
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Delayed Energy SignalPrompt Energy Signal
1 MeV 8 MeV
6 MeV 10 MeV
Efficiency & Energy Calibrations
• Stopped positron signal using 68Ge source (2 x 0.511 MeV)
e+ threshold• Neutron (n source, spallation) capture signal
• 2.2 MeV e+ energy scale • 8 MeV neutron threshold at 6 MeV
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Calibration Program
• Routine (weekly) deployment of sources.
• LED light sources
• Radioactive sources = fixed energy
• Tagged cosmogenic background (free) = fixed energy and time (electronics requirement)
Automated calibration system
e+ and neutron sources for energy calibration
Monitoring system for optical properties
/E = 0.5% per pixelRequires:1 day (near)10 days (far)
(relative)
Rates and Backgrounds
4 near detectors
signal
9Li
Site Preparation
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Assembly Building
Portal of Tunnel
Daya Bay Near Hall construction (100m underground)
Tunnel lining
Hardware Progress
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4m Acrylic Vessel Prototype
SSV Prototype
Calibration Units
Transporter
Detector AssemblyDelivery of 4m AV
SS Tank delivery
Clean Room
Sensitivity to Sin2213
• Experiment construction: 2008-2011• Start acquiring data: 2011• 3 years running
90% CL, 3 years
Project Schedule
• October 2007: Ground breaking• August 2008: CD3 review (DOE start of construction)• March 2009: Surface Assembly Building occupancy• Summer 2009: Daya Bay Near Hall occupancy• Fall 2009: First AD complete• Summer 2010: Daya Bay Near Hall ready for data• Summer 2011: Far Hall ready for data
(3 years of data taking to reach goal sensitivity)
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