The Daya Bay Reactor Neutrino Experiment

R. D. McKeownCaltech

On 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 NPPLocation

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 scintillator192 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-LABTwo 1000L 0.5% Gd-

LAB5000L 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)

Abs

orpt

ion

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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 MeV6 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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