The Daya Bay Reactor Neutrino Experiment

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

10

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

12

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

13

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

16

Assembly Building

Portal of Tunnel

Daya Bay Near Hall construction (100m underground)

Tunnel lining

Hardware Progress

17

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)

21