Asian Reactor Anti-Neutrino Experiments DAYA BAY and RENO

Asian Reactor Anti-Neutrino Experiments DAYA BAY and RENO Christopher White Illinois Institute of Technology and Lawrence Berkeley National Laboratory Neutrino 2008 - Christchurch, New Zealand 26 May 2008

Measuring sin 22 13 with reactors Long-baseline accelerator exp. Pme ≈ sin 2 23 sin 22 13 sin 2(1. 27 Dm 223 L/E) + cos 2 23 sin 22 12 sin 2(1. 27 Dm 212 L/E) A( ) cos 2 13 sin 13 sin(d) Reactor experiment Pex sin 22 13 sin 2 (1. 27 Dm 213 L/E) + cos 4 13 sin 22 12 sin 2 (1. 27 Dm 212 L/E) • No ambiguity, independent of d and matter effect A( ) • Relatively cheap compared to accelerator-based experiments • Rapid deployment possible 2

Reactor e e/Me. V/fisso n • Fission processes in nuclear reactors produce a huge number of low-energy e Resultant e spectrum known to ~1% 3 GWth generates 6 x 1020 e per sec 3

Detecting in liquid scintillator: Inverse -decay Reaction • Detect inverse -decay reaction in 0. 1% Gd-doped liquid scintillator: e p e+ + n (prompt) 0. 3 b 50, 000 b + p D + (2. 2 Me. V) (delayed) + Gd Gd* Gd + ’s(8 Me. V) (delayed) • Time- and energy-tagged signal is a good tool to suppress background events. • Energy of e is given by: E Te+ + Tn + (mn - mp) + m e+ Te+ + 1. 8 Me. V 10 -40 ke. V 4

Daya Bay: Goal And Approach • Utilize the Daya Bay nuclear power complex to: determine sin 22 13 with a sensitivity of 0. 01 by measuring deficit in e rate and spectral distortion. sin 22 13 = 0. 01 2 3 4 5 6 7 8 9 10 energy (Me. V) 5

The Daya Bay Collaboration Europe (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 6

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 reactorrelated 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) 7

Location of Daya Bay 55 km 8

The Daya Bay Nuclear Power Complex • 12 th 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 NPP: 2 2. 9 GWth Daya Bay NPP: 2 2. 9 GWth Ling Ao II NPP: 2 2. 9 GWth Ready by 2010 -2011 9

How To Measure 13 With a Reactor ? • Since reactor e are low-energy, it is a disappearance experiment: • 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 Disappearance probability Small-amplitude oscillation due to 13 integrated over E Large-amplitude oscillation due to 12 Sin 22 13 = 0. 1 m 231 = 2. 5 x 10 -3 e. V 2 Sin 22 12 = 0. 825 m 221 = 8. 2 x 10 -5 e. V 2 far detector near detector 10

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 9 Li Ideal case with a single reactor Daya Bay m 2 = 1. 8 10 -3 e. V 2 m 2 = 2. 4 10 -3 e. V 2 m 2 = 2. 9 10 -3 e. V 2 11

Daya Bay: Experimental Setup Far site Overburden: 355 m 900 m Empty detectors: moved to underground halls via access tunnel. Filled detectors: transported between halls via horizontal tunnels. Ling Ao Near Overburden: 112 m 465 m 810 m Water hall Liquid Scintillator hall Entrance Daya Bay Near Overburden: 98 m Ling Ao II cores Construction tunnel Ling Ao cores 295 m Daya Bay cores 12

Daya Bay Is Moving Forward Quickly Groundbreaking Ceremony: Oct 13, 2007 First Blast: Feb 19, 2008 Access Tunnel Entrance Moving forward… Construction Tunnel Entrance 13

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) Calibration system Steel tank • Low-background 8” PMT: 192 • Reflectors at top and bottom PMT Mineral oil Liquid Scint. 20 -t Gd-LS ~ 12% / E 5 m 1/2 3. 1 m acrylic tank 4. 0 m acrylic tank 5 m 14

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Systematic Uncertainty Control 17

AV Prototypes Under Construction… 4 -m prototype in the U. S. 3 -m prototype in Taiwan 18

Automated Calibration System elec. interface Calib. box MO overflow MO fill monitor MO overflow HKU MO clarity device Each unit deploys 3 sources: 68 Ge, 252 Cf, LED Major Prototype Test Results: • Completed >20 years worth of cycling • No liquid dripping problem • Tested limit switch precision and reliability 19

Fast neutrons per day (far site) Shielding Antineutrino Detectors Neutron background vs thickness of water 0. 30 0. 25 0. 20 2. 5 m of water 0. 15 2. 5 m of water 0. 10 0. 05 0. 1. 2. water thickness (m) • 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 20

Water 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) 21

RPC Cover Water Pool 22

Electronics and Readout System 23

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% 24

Sensitivity of Daya Bay Goal: Sin 22 13 < 0. 01 Far (80 t) • Use rate and spectral shape • input relative detector syst. error of 0. 38%/detector LA (40 t) 90% confidence level Dy. B (40 t) Sensitivity 2 near + far (3 years) Year 25

Summary • Daya Bay will reach a sensitivity of ≤ 0. 01 for sin 22 13 • 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 26

Current Status of RENO Slides courtesy of Dr. Soo-Bong Kim

Google Satellite View of Yeong. Gwang Site 28

Comparison of Reactor Neutrino Experiments Location Thermal Power (GW) Distances Near/Far (m) Depth Near/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 40 2/80 29

Rock quality map • Near detector site: - tunnel length : 110 m - overburden height : 46. 1 m • Far detector site: - tunnel length : 272 m - overburden height : 168. 1 m 30

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 31

Electronics § Use SK new electronics (will be ready in Sep. , 2008) 32

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 33

Systematic Errors Systematic Source RENO (%) Reactor antineutrino flux and cross section 1. 9 < 0. 1 Reactor power 0. 7 < 0. 1 Energy released per fission 0. 6 < 0. 1 H/C ratio 0. 8 0. 2 Target mass 0. 3 < 0. 1 Positron energy 0. 8 0. 2 Positron geode distance Reactor related absolute normalization CHOOZ (%) 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 2. 7 < 0. 6 Number of protons in target Detector Efficiency combined 34

RENO Expected Sensitivity New!! (full analysis) 10 x better sensitivity than current limit 35

Summary of Construction Status q 2007: Geological survey and tunnel design completed. q 2008: Tunnel construction q. Hamamatsu 10” PMTs are being considered - delivery starting 3/09 q. SK new electronics are adopted and ordered - 9/08 q. Steel/acrylic containers and mechanical structure ordered soon. q. Liquid scintillator handling system is being designed. q. Mock-up detector (~1/4 in length) will be built in June, 2008. Activities 2006 3 6 2007 9 12 3 6 2009 2008 9 12 3 6 9 12 Detector Design & Specification Geological Survey & Tunnel Design Detector Construction Excavation & Underground Facility Construction Detector Commissioning 36

Summary Status Report - RENO q RENO is suitable for measuring 13 (sin 2(2 13) > 0. 02) q Geological survey and design of access tunnels & detector cavities are completed. Civil construction will begin in early June, 2008. q RENO is under construction phase. q Data taking is expected to start in early 2010. q TDR will be ready in June of 2008. q International collaborators are being invited. 37

Thank You 38