Christopher WhiteIllinois Institute of Technology

andLawrence Berkeley National Laboratory

Neutrino 2008 - Christchurch, New Zealand26 May 2008

Asian Reactor Anti-Neutrino Experiments

DAYA BAY and RENO

2

Measuring sin22with reactors

• No ambiguity,independent of and matter effect A()

• Relatively cheap compared to accelerator-based experiments

• Rapid deployment possible

Long-baseline accelerator exp.

Pe ≈ sin2sin22sin2(1.27m2L/E) +

cos2sin22sin2(1.27m212L/E)

A()cos213sinsin()

Reactor experiment

Pex sin22sin2 (1.27m2L/E) +

cos4sin22sin2 (1.27m2L/E)

3

Reactor e

• Fission processes in nuclear reactors produce a huge number of low-energy

e

e/M

eV

/fiss

on

Resultant e spectrumknown to ~1%

3 GWth generates 6 x 1020 e per sec

4

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Detecting in liquid scintillator:Inverse -decay Reaction

e p e+ + n (prompt)

+ p D + (2.2 MeV) (delayed) + Gd Gd*

Gd + ’s(8 MeV) (delayed)

• Time- and energy-tagged signal is a good tool to suppress background events.

• Detect inverse -decay reaction in 0.1% Gd-doped liquid scintillator:

0.3b

50,000b

• Energy of e is given by:

E Te+ + Tn + (mn - mp) + m e+ Te+ + 1.8

MeV 10-40 keV

5

Daya Bay: Goal And Approach

• Utilize the Daya Bay nuclear power complex to:

determine sin2213 with a sensitivity of 0.01

by measuring deficit in e rate and spectral distortion.

0.985

0.99

0.995

1

0 1 2 3 4 5 6 7 8Rat

io(1

.8 k

m/P

redi

cted

fro

m 0

.3 k

m)

Prompt Energy (MeV)

sin2213 = 0.01

2 3 4 5 6 7 8 9 10

energy (MeV)

6

The Daya Bay CollaborationEurope (3) (9)

JINR, Dubna, Russia

Kurchatov Institute, Russia

Charles University, Czech Republic

North America (14)(~73)BNL, Caltech, George Mason Univ.,

LBNL, Iowa State Univ., Illinois Inst. Tech.,

Princeton, RPI, UC-Berkeley, UCLA,

Univ. of Houston, Univ. of Wisconsin,

Virginia Tech.,

Univ. of Illinois-Urbana-Champaign

Asia (18) (~125)IHEP, Beijing Normal Univ., Chengdu Univ. of Sci. and Tech., CGNPG, CIAE, Dongguan

Polytech. Univ., Nanjing Univ., Nankai Univ., Shandong Univ., Shenzhen Univ.,

Tsinghua Univ., USTC, Zhongshan Univ., Univ. of Hong Kong,

Chinese Univ. of Hong Kong, National Taiwan Univ., National Chiao Tung

Univ., National United Univ.

~ 207 collaborators

7

How To Reach A Precision of 0.01 in Daya Bay?

• Increase statistics:– Use more powerful nuclear reactors

– Utilize larger target mass, hence larger detectors

• Suppress background:– Go deeper underground to gain overburden for reducing

cosmogenic background

• Reduce systematic uncertainties:– Reactor-related:

• Optimize baseline for best sensitivity and smaller residual reactor-related errors

• Near and far detectors to minimize reactor-related errors– Detector-related:

• Use “Identical” pairs of detectors to do relative measurement• Comprehensive program in calibration/monitoring of detectors• Interchange near and far detectors (optional)

8

Location of Daya Bay

55 k

m

9

Daya Bay NPP:2 2.9 GWth

The Daya Bay Nuclear Power Complex• 12th most powerful in the world (11.6 GWth)• One of the top five most powerful by 2011 (17.4 GWth)• Adjacent to mountain, easy to construct tunnels to reach underground labs with sufficient overburden to suppress cosmic rays

Ling Ao II NPP: 2 2.9 GWth

Ready by 2010-2011

Ling Ao NPP: 2 2.9 GWth

10

How To Measure 13 With a Reactor ?

P(e x) sin2 213 sin2 m312 L

4E

cos4 13 sin2 212 sin2 m21

2 L

4E

• Go underground to reduce cosmogenic background• Place near detector(s) close to reactor(s) to measure flux and spectrum of e for normalization, hence reducing reactor-related systematic• Position a far detector near the first oscillation maximum to get the highest sensitivity, and also be less affected by 12

• Since reactor e are low-energy, it is a disappearance experiment:

Large-amplitudeoscillation due to 12

Small-amplitude oscillation due to 13

integrated over E

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

neardetector

fardetector

Sin2 = 0.1m2

31 = 2.5 x 10-3 eV2

Sin2 = 0.825m2

21 = 8.2 x 10-5 eV2

Dis

appe

aran

ce p

roba

bili

ty

11

Baseline optimization and site selection

Inputs to the process:– Flux and energy spectrum of reactor antineutrino– Systematic uncertainties of reactors and detectors– Ambient background and uncertainties– Position-dependent rates and spectra of cosmogenic neutrons

and 9Li

m2 = 1.8 10-3 eV2

m2 = 2.4 10-3 eV2

m2 = 2.9 10-3 eV2

0

0.02

0.04

0.06

0.08

0.1

0 1 2 3 4 5

Pdi

s

Baseline (km)

Ideal case with a single reactor Daya Bay

12Daya Bay

cores

Ling Aocores

Ling Ao IIcores

Liquid Scintillator

hall

Entrance

Construction tunnel

Waterhall

Empty detectors: moved to underground halls via access tunnel.Filled detectors: transported between halls via horizontal tunnels.

295 m

810 m

465 m

900 m

Daya Bay NearOverburden: 98 m

Ling Ao NearOverburden: 112 m

Far siteOverburden: 355 m

Daya Bay: Experimental Setup

13

First Blast: Feb 19, 2008

Construction Tunnel Entrance

Access Tunnel Entrance

Moving forward…

Daya Bay Is Moving Forward QuicklyGroundbreaking Ceremony: Oct 13, 2007

14

Antineutrino Detectors• Three-zone cylindrical detector design

– Target: 20 t (0.1% Gd LAB-based LS)– Gamma catcher: 20 t (LAB-based LS)– Buffer : 40 t (mineral oil)

• Low-background 8” PMT: 192

• Reflectors at top and bottom

3.1m acrylic tank

PMT

4.0m acrylic tank

Steel tankCalibrationsystem

20-t Gd-LS

Liquid Scint.

Mineral oil

12% / E1/25m

5m

15

16

Stabi l i ty of Gd- LS i n Prototype(started at 2007-2- 8)

245

255

265

275

285

1 13 25 37 49 61 73 85 97 109

121

133

145

157

days

P.E.

/MEV Cs137

Co60

17

Systematic Uncertainty Control

18

AV Prototypes Under Construction…

3-m prototype in Taiwan

4-m prototype in the U.S.

19

Automated Calibration System

Major Prototype Test Results:• Completed >20 years worth of cycling• No liquid dripping problem• Tested limit switch precision and reliability

Each unit deploys 3 sources:68Ge, 252Cf, LED

MO overflow

MO overflow

Calib. boxelec. interface

HKU MO clarity device

MO fill monitor

20

Shielding Antineutrino Detectors

• Detector modules enclosed by 2.5 m of water to shield energetic neutrons produced by cosmic-ray muons and gamma-rays from the surrounding rock

2.5 m ofwater

Neutron background vs thickness of water

Fast

neutr

ons

per

day (

far

site

)

water thickness (m)

0.05

0.10

0.15

0.20

0.25

0.30

0. 1. 2.

2.5 m ofwater

21

Water Pool – Two RegionsWater Pool – Two Regions

• Divided by Tyvek into Inner and Outer regions • Reflective Paint on ADs improves efficiency

• Calibration LEDs placed according to simulations

160 PMTs (Inner)224 PMTs (Outer)

22

RPC Cover over Water Pool

23

Electronics and Readout System

24

Signal, Background, and Systematic

• Summary of signal and background:

• Summary of statistical and systematic budgets:

Source Uncertainty

Reactor power 0.13%

Detector (per module) 0.38% (baseline)0.18% (goal)

Signal statistics 0.2%

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

25

Sensitivity of Daya Bay

DyB (40 t)

LA (40 t)

Far (80 t)

• Use rate and spectral shapeUse rate and spectral shape• input relative detector input relative detector syst. error of 0.38%/detectorsyst. error of 0.38%/detector

90% confidence level90% confidence level

2 n

ear +

far (3

years)

Goal: Sin2213 < 0.01

Year

Sens

itiv

ity

26

Summary

• Daya Bay will reach a sensitivity of ≤ 0.01 for sin2213

• Civil construction has begun

• Subsystem prototypes exist

• Long-lead orders initiated

• Daya Bay is moving forward:

– Surface Assembly Building - Summer 2008

– DB Near Hall - installation activities begin early in 2009

– Assembly of first AD pair - Spring 2009

– Commission Daya Bay Hall by November 2009

– LA Near and Far Hall - installation activities begin late in 2009

– Data taking with all eight detectors in three halls by Dec. 2010

Current Status of RENOSlides courtesy of Dr. Soo-Bong Kim

28

Google Satellite View of YeongGwang Site

29

Comparison of Reactor Neutrino Experiments

Experiments LocationThermal Power(GW)

DistancesNear/Far

(m)

DepthNear/Far

(mwe)

Target Mass(tons)

Double-CHOOZ France 8.7 280/1050 60/300 10/10

RENO Korea 17.3 290/1380 120/450 16/16

Daya Bay China 11.6 360(500)/1985(1613) 260/910 402/80

30

Rock quality map

• Near detector site: - tunnel length : 110m

- overburden

height : 46.1m

• Far detector site: - tunnel length : 272m- overburden

height : 168.1m

31

RENO Detector

Inner Diameter

(cm)

Inner Height (cm)

Filled with Mass (tons)

Target Vessel

280 320 Gd(0.1%) + LS

16.5

Gamma catcher

400 440 LS 30.0

Buffer tank

540 580 Mineral oil 64.4

Veto tank 840 880 water 352.6

total ~460 tons

32

Electronics

Use SK new electronics(will be ready in Sep., 2008)

33

Mockup Detector

Target + Gamma Catcher Acrylic Containers(PMMA: Polymethyl Methacrylate or Plexiglass)

Target Diameter 61 cm

Height 60 cm

Gamma Catcher

Diameter 120 cm

Height 120 cm

Buffer Diameter 220 cm

Height 220 cm

Buffer Stainless Steel Tank

34

Systematic Errors

Systematic Source CHOOZ (%) RENO (%)

Reactor related absolute

normalization

Reactor antineutrino flux and cross section

1.9 < 0.1

Reactor power 0.7 < 0.1

Energy released per fission 0.6 < 0.1

Number of protons in target

H/C ratio 0.8 0.2

Target mass 0.3 < 0.1

Detector Efficiency

Positron energy 0.8 0.2

Positron geode distance 0.1 0.0

Neutron capture (H/Gd ratio) 1.0 < 0.1

Capture energy containment 0.4 0.1

Neutron geode distance 0.1 0.0

Neutron delay 0.4 0.1

Positron-neutron distance 0.3 0.0

Neutron multiplicity 0.5 0.05

combined 2.7 < 0.6

35

RENO Expected Sensitivity

10x better sensitivity than current limit

New!! (full analysis)

36

Summary of Construction Status

2007: Geological survey and tunnel design completed.2008: Tunnel constructionHamamatsu 10” PMTs are being considered - delivery starting 3/09SK new electronics are adopted and ordered - 9/08Steel/acrylic containers and mechanical structure ordered soon.Liquid scintillator handling system is being designed.Mock-up detector (~1/4 in length) will be built in June, 2008.

Activities

Detector Design& Specification

Geological Survey& Tunnel Design

DetectorConstruction

Excavation &Underground Facility

Construction

DetectorCommissioning

2006 2007 2008 20093 6 9 12 3 6 9 12 3 6 9 12 3 6 9 12

37

Summary Status Report - RENO

RENO is suitable for measuring 13 (sin2(213) > 0.02)

RENO is under construction phase.

Geological survey and design of access tunnels & detector cavities are completed. Civil construction will begin in early June, 2008.

International collaborators are being invited.

TDR will be ready in June of 2008.

Data taking is expected to start in early 2010.

38

Thank You