The Daya Bay Reactor Neutrino Experiment

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The Daya Bay Reactor Neutrino Experiment

• R. D. McKeown
• Caltech

On Behalf of the Daya Bay Collaboration
CIPANP 2009
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Maki Nakagawa Sakata Matrix
Gateway to CP Violation!
CP violation
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ne Survival Probability
Dominant ?12 Oscillation
Subdominant ?13 Oscillation

• Clean measurements of q, Dm2
• No CP violation
• Negligible matter effects

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Daya Bay Nuclear Power Plant

• 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

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Daya Bay NPP Location
55 km
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Experiment Layout

• Multiple detectors
• per site cross-check
• detector efficiency
• Two near sites
• sample flux from
• reactor groups

20T
Total Tunnel length 3000 m
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Antineutrino Detector
Calibration units
ne p ? e n n capture on Gd (30 ms delay)
20 T Gd-doped liquid scintillator
192 8 PMTs
Gamma catcher
Buffer oil

• 3 zone design
• Uniform response
• No position cut
• 12/v E resolution

Acrylic Vessels
SS Tank
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Muon Veto System
RPCs
Water Cerenkov (2 layers)
Redundant veto system ? 99.5 efficient muon
rejection
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Gd-Liquid Scintillator Test Production
Daya Bay experiment uses 200 ton 0.1
gadolinium-loaded liquid scintillator (Gd-LS).
Gd-TMHA LAB 3g/L PPO 15mg/L bis-MSB
500L fluor-LAB
Two 1000L 0.5 Gd-LAB
5000L 0.1 Gd-LS
0.1 Gd-LS in 5000L tank
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.
Production Steps 1. Produce Gd solid2. Dissolve
the Gd solid in LAB and get 0.5 Gd-LAB3.
Dissolve fluors in 500L LAB4. Mix 1000L 0.5
Gd-LAB, 500L fluors-LAB, and LAB, to form 0.1
Gd-LS
Daya Bay production of 185 ton of 0.1 Gd-LS,
4-ton per batch test batch production of 3.7
ton 0.1 Gd-LS
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Controlling Systematic Uncertainties
Measured Ratio of Rates
Storage Tank
flow mass measurement
Far
Near
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Target Mass Measurement
filling platform with clean room
ISO Gd-LS weighing tank
pump stations
20-ton, teflon-lined ISO tank
Gd-LS
MO
LS
detector
Coriolis mass flowmeters lt 0.1
load cell accuracy lt 0.02
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Efficiency Energy Calibrations
Prompt Energy Signal
Delayed Energy Signal

• 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
Automated calibration system

• Routine (weekly) deployment of sources.
• LED light sources
• Radioactive sources fixed energy
• Tagged cosmogenic background (free) fixed
  energy and time (electronics requirement)

Monitoring system for optical properties
e and neutron sources for energy calibration
s/E 0.5 per pixel Requires 1 day (near) 10
days (far)
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(relative)
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Rates and Backgrounds
9Li
n signal
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Site Preparation
Daya Bay Near Hall construction (100m underground)
Assembly Building
Tunnel lining
Portal of Tunnel
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Hardware Progress
SSV Prototype
4m Acrylic Vessel Prototype
Transporter
Calibration Units
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Detector Assembly
Delivery of 4m AV
SS Tank delivery
Clean Room
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Sensitivity to Sin22q13

90 CL, 3 years

• Experiment construction 2008-2011
• Start acquiring data 2011
• 3 years running

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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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