feb9a78e507554797c11620d7c5c78e1.ppt
- Количество слайдов: 30
Daya Bay Experiment Steve Kettell BNL On Behalf of the Daya Bay Collaboration S. Kettell WIN 09 9/13/09
The Last Mixing Angle: 13 ? UMNSP Matrix Maki, Nakagawa, Sakata, Pontecorvo atmospheric, K 2 K reactor and accelerator 23 = ~ 45° 13 = ? SNO, solar SK, Kam. LAND 12 ~ 32° 0 ? • What is e fraction of 3? • Is there symmetry in neutrino mixing? • Will we be able to observe CP violation? • Ue 3 is the gateway to leptonic CP violation. S. Kettell WIN 09 9/13/09 2
Detection of e Inverse -decay in Gd-doped liquid scintillator: e p e+ + n (prompt) 0. 3 b + p D + (2. 2 Me. V) 50 kb + Gd Gd* Gd + ’s(8 Me. V) (delayed) Prompt Energy Signal Delayed Energy Signal 1 Me. V 10 Me. V 6 Me. V n-p • Ee+ = [1, 8] Me. V • En (delayed) = [6, 10] Me. V. • tdelayed-tprompt = [0. 3, 200] s n-Gd • Calibrate with 68 Ge, neutron, and 60 Co • additional calibration with LED and spallation neutrons S. Kettell WIN 09 9/13/09 3
Measuring 13 at a Reactor • Precise measurement • No dependence on CP or matter effects P ee Disappearance Probability detector 1 detector 2 nuclear reactor MO LS 13 Gd-LS Distance (km) ~1. 8 km ~ 0. 3 -0. 5 km S. Kettell WIN 09 9/13/09 • near detectors measure e flux and spectrum to reduce reactor-related systematic uncertainties • far detector at the oscillation max provides the highest sensitivity 4
Measurement Concept Measure ratio of interaction rates in multiple detectors νe near Measured Ratio of Rates Gd-LS Storage Tank Detector Mass Ratio, H/C mass measurement Near Far distance L ~ 1. 5 km Detector Efficiency Ratio far sin 22 13 calibration ± 0. 3% S. Kettell WIN 09 9/13/09 ± 0. 2% 5
Total tunnel length: ~2700 m 0 m 91 Far site 1600 m from Ling Ao 2000 m from Daya Overburden: 350 m 2010 -11 570 m 730 m Water hall Ling Ao Near 500 m from Ling Ao Overburden: 98 m Ling Ao II: Ling Ao: 2 2. 9 GWth 1 GWth generates 2 × 1020 e /s Filling hall Daya Bay Near 360 m from Daya Bay Overburden: 97 m Total Power Now: 11. 6 GWth 2011: 17. 4 GWth Daya Bay NPP: S. 2. 9 GWth 2 Kettell WIN 09 9/13/09 6
Daya Bay Detectors • 8 Antineutrino detectors • 4 in far hall, 2 in each near hall • 20 t target mass per AD • Muon Veto system Ancillary Rooms - Gas - DAQ - Water S. Kettell WIN 09 9/13/09 7
Muon Veto System 1 m outer water veto 1. 5 m inner water veto Water Cerenkov (2 layers) 960 8” PMTs (3 pools) RPC AD Multiple muon detectors: § Water pool Cherenkov counter: inner/outer regions, 2. 5 m shield § RPC muon tracker § Combined efficiency (99. 5 0. 25)% S. Kettell WIN 09 9/13/09 8
Anti-neutrino Detector (AD) Design Calibration System I. III. q q Eight identical 3 -zone detectors: Target: 20 t Gd-LS -catcher: 20 t LS Buffer shielding: 40 t mineral oil MO Top/bottom reflectors 192 8”PMT/module Reflectors LS Gd-LS 1. 55 m s. E/E = 12%/ E ~ 12% / E 1/2 1. 99 m PMT 2. 49 m Acrylic Total Weight = 110 t S. Kettell WIN 09 9/13/09 Vessels 5 m q 9
(Gd) Liquid Scintillator Daya Bay experiment uses 185 ton 0. 1% gadolinium-loaded liquid scintillator (Gd. LS). Gd-TMHA + LAB + 3 g/L PPO + 15 mg/L bis-MSB 500 L fluor-LAB Two 1000 L 0. 5% Gd. LAB 5000 L 0. 1% Gd. LS 0. 1% Gd-LS in 5000 L tank Gd-LS stability in 4 T test 4 -ton test batch production in March 2009. Gd-LS will be produced in multiple batches but mixed in reservoir on-site to ensure identical detectors. S. Kettell WIN 09 9/13/09 10
Daya Bay Background 840 backgrounds from beta-delayed neutron emission isotopes 8 He and 9 Li will have to be measured and subtracted 9 Li 4 near detectors ν signal S. Kettell WIN 09 9/13/09 11
Systematic Uncertainties CHOOZ: R=1. 01 2. 8%(stat) 2. 7%(syst), sin 22 13<0. 17 Detector-Related Uncertainties Absolute measurement Relative measurement O(0. 2 -0. 3%) precision for relative measurement between detectors at near and far sites S. Kettell WIN 09 9/13/09 Ref: Daya Bay TDR 12
Sensitivity: sin 22θ 13 < 0. 01 @ 90% CL after 3 years of data taking Sensitivity in sin 22 13 (90%CL) Daya Bay Sensitivity 0. 05 0. 38% relative detector syst. uncertainty m 231 = 2. 5 10 3 e. V 2 0. 04 0. 03 0. 02 0. 01 0. 0 1 2 3 4 5 Number of years of data taking Source Reactor power Detector (per module) Signal statistics Uncertainty 0. 13% 0. 38% (baseline) 0. 2% Steps to Physics: • Dry-Run • near site operations S. Kettell WIN 09 9/13/09 • Full operations 13
Daya Bay Project Status • CD-0 (DOE Mission Need): 11/2005 Far hall • Daya Bay proposed at OHEP Briefing 4/2006 • Successful Physics Review 10/16/06 August 2009 • CD-1 site selection approved 9/2007 • Groundbreaking for civil construction 10/2007 • CD-2 Baseline approved 3/2008 • CD-3 b Construction start 8/2008 • Occupancy of SAB 3/2009 • Occupancy of first underground halls, fall 2009 • Expected start of first operations, summer 2010 • Full operations start, summer 2011 Ling Ao hall LS hall S. Kettell WIN 09 9/13/09 Daya Bay hall 14
Civil Construction Control Room Entrance Daya Bay Near Hall - July 09 Surface Assembly Building S. Kettell WIN 09 9/13/09 15
Detector Assembly 0. 1% Gd-LS in 5000 -L tank 3 -m acrylic vessel in Taiwan SS Vessel Reflector delivery to SAB S. Kettell WIN 09 9/13/09 4 -m vessel in the U. S. Prototype assembly in SAB 16
Summary and Conclusions The Daya Bay experiment is the most sensitive reactor θ 13 experiment under construction and is designed to measure sin 22θ 13 < 0. 01 at 90% CL with 3 years of data taking. • Daya Bay will use eight “identical” antineutrino detectors to achieve a relative detector systematic error < 0. 38%. The 3 -zone detector design allows the observation of the antineutrino signal without fiducial cuts. • Civil and detector construction are progressing well. Data taking at the near site is scheduled to begin in summer 2010 with 2 detectors, which will allow extensive studies of systematics. • The full experiment will begin in summer 2011. • Detectors are movable. Swapping can be considered after some running to further reduce systematic uncertainties but is not required to reach the baseline sensitivity. S. Kettell WIN 09 9/13/09 17
Daya Bay Collaboration Europe (3) (9) United States (15)(~89) BNL, Caltech, U. Cincinnati, George Mason U, LBNL, Iowa State U, Illinois Inst. Tech. , Princeton, RPI, UC-Berkeley, UCLA, U. of Houston, U. of Wisconsin, Virginia Tech. , U. of Illinois-Urbana-Champaign JINR, Dubna, Russia Kurchatov Institute, Russia Charles University, Czech Republic ~ 230 collaborators Asia (19) (~135) IHEP, Beijing Normal U. , Chengdu U. of Sci. and Tech. , CGNPG, CIAE, Dongguan Polytech. U. , Nanjing U. , Nankai U. , Shandong U. , Shanghai Jiaotong U. , Shenzhen U. , Tsinghua U. , USTC, Zhongshan U. , U. of Hong Kong, Chinese U. of Hong Kong, National Taiwan U. , National Chiao Tung U. , National United U. S. Kettell WIN 09 9/13/09 18
Backup S. Kettell WIN 09 9/13/09 19
Phase-I, started in 2006, ended in Jan. 2007 S. Kettell WIN 09 9/13/09 20
IHEP Prototype (0. 1% Gd-LS) Gd-TMHA complex synthesis Phase-II, filled with half-ton 0. 1% Gd-LS, started in Jan. 2007 and keep running until now. The prototype is also used for the FEE and Trigger boards testing. S. Kettell WIN 09 9/13/09 21
Calibration system Automated calibration system → routine weekly deployment of sources LED light sources → monitoring optical properties • 68 Ge source • Am-13 C + 60 Co source • LED diffuser ball e+ and n radioactive sources (=fixed energy) → energy calibration automated calibration system S. Kettell WIN 09 9/13/09 22
Daya Bay Antineutrino Detectors 3 -Zone Design oil buffer (MO) thickness no position reconstruction, no fiducial cut for event identification > 15 cm buffer between PMT and OAV MO Gd-LS (20 tons) LS Efficiency (%) gamma catcher (LS) thickness = 42. 3 cm det. efficiency > 91. 5% = 5 m (tunnel limitations) S. Kettell WIN 09 9/13/09 23
Detector Top/Bottom Reflectors specular reflectors consist of ESR® high reflectivity film on acrylic panels total p. e reflector flattens detector response without reflector with reflector z (cm) S. Kettell WIN 09 9/13/09 z (cm) 24 24
Antineutrino Detector Response Detector Uniformity along radial R direction Gd-LS boundary along vertical symmetry axis (zdirection) Gd-LS boundary - GEANT 4 -based simulations - idealized 3 -zone detector plus reflectors - developing realistic geometry in simulations S. Kettell WIN 09 9/13/09 25
Detector Calibration LED light sources → monitoring optical properties e+ and n radioactive sources (=fixed energy) → energy calibration automated calibration system tagged cosmogenic background (free) → fixed energy and time z(cm) automated calibration system → routine weekly deployment of sources R(cm) 68 Ge source Am-C + 60 Co source LED diffuser ball σ/E = 0. 5% per pixel requires: 1 day (near), 10 days (far) S. Kettell WIN 09 9/13/09 26
Energy calibration Prompt Energy Signal 1 Me. V + Delayed Energy Signal ν e + p →e + n 8 Me. V 6 Me. V e+ threshold: stopped positron signal using 68 Ge source (2 x 0. 511 Me. V) e+ energy scale: 2. 2 Me. V neutron capture signal (n source, spallation) 1 Me. V cut for prompt positrons: >99%, uncertainty negligible 10 Me. V 6 Me. V threshold: n capture signals at 8 and 2. 2 Me. V (n source, spallation) 6 Me. V cut for delayed neutrons: 91. 5%, uncertainty 0. 22% assuming 1% energy uncertainty efficiency 98% S. Kettell WIN 09 9/13/09 efficiency 78% 27
Target mass measurement 200 -ton Gd-LS reservoir ISO Gd-LS weighing tank filling platform with clean room pump stations 20 -ton ISO tank LS Gd-LS detector MO load cell accuracy < 0. 02% Coriolis mass flowmeters < 0. 1% S. Kettell WIN 09 9/13/09 filling “pairs” of detectors 28
Nuclear reactors as antineutrino source • The observable antineutrino spectrum is the product of the flux and the cross section Arbitrary • Fission process in nuclear reactor produces huge number of low-energy antineutrino • A typical commercial reactor, with 3 GW thermal power, produces 6× 1020νe/s • Daya Bay reactors produce 11. 6 GWth now, 17. 4 GWth in 2011 From Bemporad, Gratta and Vogel Antineutrino spectrum x Flu S. Kettell WIN 09 9/13/09 s. S os ion ct e Cr 29
Proposed Reactor Experiments Krasnoyarsk, Russia Braidwood, USA Diablo Canyon, USA RENO, Korea sin 22 13~0. 03 Double Chooz, France sin 22 13~0. 03 KASKA, Japan Daya Bay, China sin 22 13~0. 01 8 proposals Angra, Brazil R&D phase 4 cancelled 4 in progress Advantages of Daya Bay: 1)very high antineutrino flux; 2) mountains to suppress cosmic-ray-induced background S. Kettell WIN 09 9/13/09 30
feb9a78e507554797c11620d7c5c78e1.ppt