Documents
Resources
Learning Center
Upload
Plans & pricing Sign in
Sign Out

Daya Bay

VIEWS: 44 PAGES: 30

									  Daya Bay Experiment
            Steve Kettell
                BNL
On Behalf of the Daya Bay Collaboration




  S. Kettell WIN09 9/13/09
            The Last Mixing Angle: 13
                                              e1 U e 2 U e 3  0.8
                                              U                                     0.5     U e 3    ?
 UMNSP Matrix                                                                               
                                         U   1 U  2 U  3  
                                              U                     0.4             0.6     0.7 
                                                              
                                                                                            0.7 
 Maki, Nakagawa, Sakata, Pontecorvo
                                              U
                                               1 U 2 U 3   0.4             0.6           

  
   1    0           0      cos13          0 ei CP sin 13   cos12    sin 12   0 1    0            0        
                                                                                                              
   0 cos 23
              sin 23  
                             0               1        0             sin 12
                                                                            cos12    0  e i / 2
                                                                                                 0                 0        
                                                                                                                  
   sin  23
   0             cos 23   i CP sin 13
                              e
                                             0    cos13   0
                                                                                 0       1 0    0       e i / 2i   



  atmospheric, K2K             reactor and accelerator            SNO, solar SK, KamLAND                   0

       23 = ~ 45°                       13 = ?                          12 ~ 32°                           ?
     • What ise fraction of 3?
     • Is there  symmetry in neutrino mixing?
     • Will we be able to observe CP violation?
          • Ue3 is the gateway to leptonic CP violation.

                           S. Kettell WIN09 9/13/09                                                                          2
                                      Detection of e

 Inverse -decay in Gd-doped liquid scintillator:
e  p  e+ + n (prompt)
           0.3b
                   + p  D + (2.2 MeV)           (delayed)
           50kb    + Gd  Gd*  Gd + ’s(8 MeV) (delayed)
     Prompt Energy Signal                                   Delayed Energy Signal


       1 MeV
                                                                         6 MeV          10 MeV




                                                                 n-p             n-Gd

   •Ee+ = [1,8] MeV
   •En (delayed) = [6,10] MeV            • Calibrate with 68Ge, neutron, and 60Co
      .                                  • additional calibration with LED and spallation neutrons
   •tdelayed-tprompt = [0.3,200] s

                          S. Kettell WIN09 9/13/09                                               3
                Measuring 13 at a Reactor
                                               m 2 L                            2 
                                                                                2 m 21 L
                         Pee  1 sin 213 sin 
                                     2        2     31
                                                         cos 13 sin 212 sin 
                                                               4       2
                                                                                          
                                                4 E                          4 E 
                                            Disappearance Probability
• Precise measurement




                                                          Pee
                                                                detector 1
• No dependence on CP or matter effects                               detector 2

                                                               nuclear reactor
           MO
                           LS


                 Gd-LS                                                  13



                                                                              Distance (km)
~1.8 km

          ~ 0.3-0.5 km                                   • near detectors measure e flux
                                                          and spectrum to reduce reactor-
                                                         related systematic uncertainties
                                                         • far detector at the oscillation max
                           S. Kettell WIN09 9/13/09      provides the highest sensitivity    4
                     Measurement Concept
Measure ratio of interaction rates in multiple detectors
                  νe

                                   distance L ~ 1.5 km
                           near                          far



Measured
Ratio of          Detector            Detector
 Rates           Mass Ratio,          Efficiency
Gd-LS Storage       H/C                 Ratio
    Tank                                             sin2213
                mass measurement     calibration
 Near     Far
                      ±                    ± 0.2%
                     0.3%
                  S. Kettell WIN09 9/13/09                      5
                                                                Ling Ao II: Ling Ao:
                                 Total tunnel length: ~2700 m
                                                                2  2.9 GWth 2  2.9 GWth
Far site                          Ling Ao Near
1600 m from Ling Ao               500 m from Ling Ao            2010-11
2000 m from Daya                  Overburden: 98 m
Overburden: 350 m


              Water hall


                         730 m
                                                                1 GWth generates 2 × 1020 e
                                                                /s
                                 Filling hall
   Daya Bay Near
   360 m from Daya Bay                                                 Total Power
   Overburden: 97 m
                                                                       Now: 11.6 GWth
                                                                       2011: 17.4 GWth




                          Daya Bay NPP:
                         S.  2.9 GWth
                          2 Kettell WIN09 9/13/09                                           6
            Daya Bay Detectors

                                       • 8 Antineutrino detectors
                                       • 4 in far hall, 2 in each
                                       near hall
                                       • 20t target mass per AD
                                       • Muon Veto system




Ancillary
Rooms
- Gas
- DAQ
- Water




            S. Kettell WIN09 9/13/09                                7
              Muon Veto System
                                               1m outer water veto
                                     1.5m inner water veto




Water
Cerenkov
(2 layers)                     RPC


960                               AD
8”
PMTs                                    Multiple muon detectors:
                                         Water pool Cherenkov counter:
(3 pools)                                 inner/outer regions, 2.5m shield
                                         RPC muon tracker
                                         Combined efficiency (99.5  0.25)%
             S. Kettell WIN09 9/13/09                                     8
          Anti-neutrino Detector (AD) Design
                                                           Calibration System
 Eight identical 3-zone detectors:
I. Target: 20t Gd-LS
II. -catcher: 20t LS
III. Buffer shielding: 40t mineral oil                              MO
 Top/bottom reflectors                                        LS
 192 8”PMT/module Reflectors
                                                      Gd-LS
                                                              1.55 m
         sE/E = 12%/E
              ~ 12% / E1/2
                                                              1.99 m




                                                                                5m
                                  PMT                         2.49 m




                                             Acrylic Total Weight = 110t
                    S. Kettell WIN09 9/13/09 Vessels                            9
                       (Gd) Liquid Scintillator
Daya Bay experiment uses 185 ton 0.1% gadolinium-loaded liquid scintillator (Gd-
LS). Gd-TMHA + LAB + 3g/L PPO + 15mg/L bis-MSB
                                500L fluor-LAB
                                            Two 1000L 0.5% Gd-
                                            LAB            5000L 0.1% Gd-
                                                          LS




                                                                                0.1% Gd-LS in
                                                                                5000L tank




                                                        Gd-LS stability in 4T 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 WIN09 9/13/09                                               10
               Daya Bay Background
                                      840




backgrounds from beta-delayed neutron emission
isotopes 8He and 9Li will have to be measured and
subtracted
         9Li                4 near detectors

      signal


                     S. Kettell WIN09 9/13/09       11
               Systematic Uncertainties
                    CHOOZ: R=1.012.8%(stat) 2.7%(syst), sin2213<0.17

Detector-Related Uncertainties
                               Absolute         Relative
                               measurement      measurement




  O(0.2-0.3%) precision for relative measurement between      Ref: Daya Bay TDR
  detectors at near and far sites

                    S. Kettell WIN09 9/13/09                                      12
                   Daya Bay Sensitivity




                                  Sensitivity in sin2213 (90%CL)
                                                                    0.05

                                                                    0.04       0.38% relative detector syst. uncertainty
Sensitivity:                                                                   m231 = 2.5  103 eV2
                                                                    0.03
sin22θ13 < 0.01 @ 90% CL
after 3 years of data taking                                        0.02

                                                                    0.01

                                                                     0.
                                                                           0         1         2       3         4         5
                                                                                  Number of years of data taking

                                                                               Source                        Uncertainty
                                                                               Reactor power                   0.13%
                                                                               Detector (per module)       0.38% (baseline)
                                                                               Signal statistics                0.2%

                                          Steps to Physics:
                                          •      Dry-Run
                                          •      near site operations
                 S. Kettell WIN09 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
• CD-1 site selection approved 9/2007             August 2009
• Groundbreaking for civil construction 10/2007
• CD-2 Baseline approved 3/2008
• CD-3b 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 WIN09 9/13/09                           14
                                                         Daya Bay hall
                          Civil Construction
                                                    Control Room
             Entrance




Daya Bay Near Hall - July 09




                                             Surface Assembly Building
                       S. Kettell WIN09 9/13/09                          15
                   Detector Assembly




0.1% Gd-LS in        3-m acrylic vessel
5000-L tank          in Taiwan              4-m vessel in the U.S.




   SS Vessel
                           Reflector
delivery to SAB S. Kettell WIN09 9/13/09   Prototype assembly in SAB
                                                                  16
         Summary and Conclusions
The Daya Bay experiment is the most sensitive reactor θ13 experiment
under construction and is designed to measure sin22θ13 < 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 WIN09 9/13/09                                 17
                  Daya Bay Collaboration
                                                                         Europe (3) (9)
                                                                       JINR, Dubna, Russia
         United States (15)(~89)                                    Kurchatov Institute, Russia
BNL, Caltech, U. Cincinnati, George Mason U,                     Charles University, Czech Republic
   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


                             ~ 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 WIN09 9/13/09                                               18
           Backup




S. Kettell WIN09 9/13/09   19
                           Phase-I, started in 2006,
                           ended in Jan. 2007




S. Kettell WIN09 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 WIN09 9/13/09   21
                        Calibration system
Automated calibration system
                                                   • 68Ge source
→ routine weekly deployment of sources             • Am-13C + 60Co source
LED light sources
                                                   • LED diffuser ball
→ monitoring optical properties
e+ and n radioactive sources (=fixed energy)
→ energy calibration




     automated calibration system


                        S. Kettell WIN09 9/13/09                            22
    Daya Bay Antineutrino Detectors
3-Zone Design
no position reconstruction, no fiducial cut for                    oil buffer (MO) thickness
event identification

                                                                        > 15cm buffer between
                                                                        PMT and OAV




                                 MO

               Gd-LS                                               gamma catcher (LS) thickness
             (20 tons)
                                LS                                                 thickness

                                                  Efficiency (%)
                                                                                   = 42.3 cm

                                                                                   det. efficiency
                                                                                   > 91.5%

        = 5m (tunnel limitations)
                      S. Kettell WIN09 9/13/09                                                       23
                  Detector Top/Bottom Reflectors




specular reflectors consist of ESR® high
reflectivity film on acrylic panels
                                                       reflector flattens detector response
                                           total p.e       without reflector




                                                                                   with reflector

                                                                      z (cm)                    z (cm)
                     S. Kettell WIN09 9/13/09                                                       24
                                                                                                         24
    Antineutrino Detector Response
Detector Uniformity

 along radial R direction                       along vertical symmetry axis
                                                (z-direction)




                 Gd-LS boundary                                Gd-LS boundary




                  - GEANT4-based simulations
                  - idealized 3-zone detector
                  plus reflectors
                  - developing realistic
                  geometry in simulations

                  S. Kettell WIN09 9/13/09                                      25
                        Detector Calibration

automated calibration system                        tagged cosmogenic background
→ routine weekly deployment of sources              (free)
                                                    → fixed energy and time
LED light sources
→ monitoring optical properties




                                                          z(cm)
e+ and n radioactive sources (=fixed energy)
→ energy calibration




                                                                              R(cm)
  automated calibration system
  68Gesource
  Am-C + 60Co source                                    /E = 0.5% per pixel requires:
  LED diffuser ball                                     1 day (near), 10 days (far)

                         S. Kettell WIN09 9/13/09                                     26
                              Energy calibration
                                                     Delayed Energy Signal e + p e + n
Prompt Energy Signal                                                                +




  1 MeV                    8 MeV

                                                                          6 MeV             10 MeV




e+ threshold: stopped positron signal using 68Ge      6 MeV threshold: n capture signals at 8 and 2.2
source (2x0.511 MeV)                                  MeV (n source, spallation)
e+ energy scale: 2.2 MeV neutron capture signal (n
source, spallation)
1 MeV cut for prompt positrons: >99%,                6 MeV cut for delayed neutrons: 91.5%,
uncertainty negligible                               uncertainty 0.22% assuming 1% energy uncertainty
                          efficiency 98%                  efficiency 78%
                         S. Kettell WIN09 9/13/09                                                       27
                   Target mass measurement
                                   ISO Gd-LS weighing tank                        filling platform
 200-ton Gd-LS reservoir                                                          with clean room


                                                         pump stations




       20-ton ISO tank
                                                                                    detector
LS   Gd-LS   MO




                         load cell
                         accuracy < 0.02%

                                             Coriolis mass               filling “pairs” of detectors
                                             flowmeters < 0.1%
                         S. Kettell WIN09 9/13/09                                                   28
   Nuclear reactors as antineutrino source
• 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




                                  Arbitrary
• The observable antineutrino                         Antineutrino spectrum
spectrum is the product of the
flux and the cross section




              S. Kettell WIN09 9/13/09                                          29
            Proposed Reactor Experiments

                                                                           RENO, Korea
                                                    Krasnoyarsk, Russia
             Braidwood, USA                                                sin2213~0.03

                                    Double Chooz, France
Diablo Canyon, USA
                                    sin2213~0.03                                KASKA, Japan

                                                               Daya Bay, China
                                                               sin2213~0.01

                                                                 8 proposals
                                    Angra, Brazil
                                                                      4 cancelled
                                    R&D phase
                                                                      4 in progress

                              Advantages of Daya Bay:
                              1)very high antineutrino flux;
                              2) mountains to suppress cosmic-ray-induced background
                       S. Kettell WIN09 9/13/09                                            30

								
To top