Antineutrino Detector Outline Requirements Overall Design Mechanics Liquid Scintillator PMTs Electronics Calibration Performance Steve Kettell BNL US Daya Bay Project Chief Scientist Director’s Review, BNL 9/28/06

Antineutrino Detector I will discuss the overall detector design, including some discussion of electronics and calibrations Bob will show the results of the studies of the systematic uncertainties Director’s Review, BNL 9/28/06

Antineutrino Detector Requirements High statistics  large, homogeneous detectors Identical detectors  precise, redundant measurements Clean inverse -decay signature with good background separation  Gd-loaded liquid scintillator (LS) (8 MeV/n-capture and 30ms capture time with 0.1% Gd) Well determined fiducial mass and hydrogen density  precise measurement of Gd-LS volume and mass (no need for vertex cut) Low threshold to detect e+ at rest  low single g rate Well-defined neutron detection efficiency  g-catcher, energy scale calibration, identical detectors Good energy resolution for energy scale, spectral distortion  high scintillation output, long Lattn, good photocathode coverage Enable transport and swapping in a reasonable tunnel size (easy to build multiple modules), manageable muon flux  moderate size Director’s Review, BNL 9/28/06

Antineutrino Detector Design Cylindrical three-Zone Structure: I. Target: 0.1% Gd-loaded liquid scintillator II. g-catcher: liquid scintillator, 45cm III. Buffer shielding: mineral oil, ~45cm 20 t Gd-LS With 224 PMT’s on circumference and diffuse reflector on ends: 12.2% 13cm Oil buffer thickness LS Rate from PMT glass oil Isotopes (from PMT) Purity (ppb) 20cm (Hz) 25cm (Hz) 30cm 40cm 238U(>1MeV) 40 2.2 1.6 1.1 0.6 232Th(>1MeV) 1.0 0.7 0.3 40K(>1MeV) 25 4.5 3.3 2.3 1.2 Total 7.7 5.6 4.0 2.1 92% g Catcher thickness A 45cm buffer provides ~20cm of shielding against PMT glass Director’s Review, BNL 9/28/06 g-catcher thickness (cm)

Antineutrino Target Mass 4 x 20 tons target mass at far site Sensitivity after 3 years. Director’s Review, BNL 9/28/06

Three zone detector 40 ton 20 ton 2-zones implies simpler design/construction, some cost reduction but with increased risk to systematic effects (neutron e and E spectrum) 3-zones provides increased confidence in systematic uncert. associated with detection efficiency and fiducial volume, but smaller volume n capture on Gd yields 8 MeV with 3-4 g’s cut 3-ZONE 2-ZONE Uncertainty ~ 0.2% Uncertainty ~ 0.4% 40 ton 20 ton 4 MeV cut can reduce the error by x2, but residual radioactivity in LS volume does not allow us to do so Director’s Review, BNL 9/28/06

Rates spectrum from Aberdeen: same granite as Daya Bay Fast neutron spectrum from MC simulation Director’s Review, BNL 9/28/06

Rates are per antineutrino detector module Source Units DB LA far 1) Antineutrino signal (day-1) 930 760 90 2) Radioactivity (Hz) 31 Rock 4 PMT glass 8 other materials (steel) 18 Gd contamination 1 3) Muons 24 14 Tagged single neutron 480 320 45 Tagged fast neutron 20 13 2 b emitters (6-10 MeV) 210 140 15 12B 400 270 28 8He+9Li 3 Rates are per antineutrino detector module Director’s Review, BNL 9/28/06

Mechanical Design Gd-LS Target: 3.2m () x 3.2m (L)  ~20 tons LS g-catcher: 4.1m () x 4.1m (L)  ~20 tons Mineral oil buffer: 5m () x 5m (L)  ~40 tons Director’s Review, BNL 9/28/06

Detector Vessel Structure Steel tank Outer acrylic tank Inner acrylic tank PMT Acrylic transparency Dimensions inner outer steel Diameter (mm): 3200 4100 5000 Height (mm): 3200 4100 5000 Wall thickness (mm): 10 15 10-20 Weight (ton): 0.6 1.4 10-25 Water Director’s Review, BNL 9/28/06

Finite Element Analysis for Steel Tank Load condition: tank structure filled with liquids Constraint condition: bottom annular surface was constrained The max. stress: 108 MPa The max. deformation: 2.8 mm Stress result Unit:Pa Deformation result Unit:m Director’s Review, BNL 9/28/06

considered in one of the civil conceptual design reports Moving the Detector Moving 100t over 0.5% tunnel grade Down 10% grade when empty (20t) Lifting 100t into water pool Bridge crane option considered in one of the civil conceptual design reports Director’s Review, BNL 9/28/06

Detector Instrumentation Monitoring Goals: - mechanical stability during filling, transport, and movement - liquid levels during filling - acrylic vessel positions mass flow volume flow temperature density CCD camera Laser reflection for in-situ measurement of: attenuation length acrylic vessel movement and position during transport level sensors tilt sensors load sensors Liquid Scintillator sampling Director’s Review, BNL 9/28/06

Detectors are filled in pairs from common storage tanks Filling the Detector Detectors are filled in pairs from common storage tanks I. Target: 0.1% Gd-loaded liquid scintillator II. g-catcher: liquid scintillator, 45cm III. Buffer shielding: mineral oil, ~45cm Three Liquids: Mass Measurements: mass + volume flow load sensors Example: Coriolis Mass Flow Measurements Gd-LS LS oil Possible mass flow rates of 1g/hr - 8000kg/hr with 0.1% repeatability. Flowmeters – 0.02% repeatability Baseline = 0.2% Goal = 0.02% Director’s Review, BNL 9/28/06

Require stable Gd-loaded liquid scintillator with Gd loading significantly increases the energy of the neutron signal and increases the number of neutron captures (within a given time window) and thereby reduces background Require stable Gd-loaded liquid scintillator with high light yield long attenuation length Director’s Review, BNL 9/28/06

Gd-Liquid Scintillator Optical Attenuation: Stable ~700 days Gd (carboxylate ligands) in pseudocumene (PC) and dodecane stable for ~2 years - attenuation Length >15m - promising alternative scintillator: Linear Alkyl Benzene (LAB) Director’s Review, BNL 9/28/06

Determination of H/C and Gd in LS Combustion Analysis Gd-LS decomposition in O2: LS: CxHy + (x + y/4).O2  x. CO2 + y/2.H2O Gd: 2.Gd +(3/2).O2  Gd2O3 Potential of measuring C, H and Gd simultaneously with good precision. Samples were measured by certified, commercial laboratory; achieved C/H measurements at 0.3%. This precision can be improved further. Determination of number of Hydrogen antineutrino targets in the scintillator Director’s Review, BNL 9/28/06

Prompt Gamma Activation Analysis Determine H and Gd in LS Prompt Gamma Activation Analysis Measure 2.2-MeV  from H; 0.18-MeV and other ’s from Gd after thermal neutron capture. Samples were measured by the Institute of Isotopes, HAS; achieved Gd and H measurement at 1%; the precision needs to be improved. Director’s Review, BNL 9/28/06

Performance of Gd in PC and LAB Optical Spectra Light Output Spectra Absorbance over 10 cm Events/nm PC Lab  (nm)  (nm) Have produced ~1% Gd in LAB and in pseudocumene (PC). (Will dilute to ~0.1% Gd in Daya Bay experiment.) LAB has lower optical absorption (longer attenuation length). LAB has better chemical and ESH properties. LAB and PC have very similar light output efficiency. Director’s Review, BNL 9/28/06

Low-radioactivity glass Two candidates PMTs 224 8” PMTs in 7 rings of 32 Low-radioactivity glass Two candidates Hamamatsu R5912 Electron Tubes 9354KB Magnetic shielding under investigation Director’s Review, BNL 9/28/06

Electronics (Front-End) Charge Specifications: Dynamic range: 0.025-500 PE Noise: < 0.1photoelecton (PE) Shaping time: 300 ns Sampling freq.: 40 MHz Time Specifications: Resolution < 500 ps Signal split two ways for ADC & TDC Director’s Review, BNL 9/28/06

Electronics (Trigger) Primary Physics Triggers: Esum: 0.7 MeV Emult: 10 PMTs Trigger rate per module: g < 50 Hz m = 24 Hz (DB), 14 Hz (LA), 1 Hz (F) Other triggers: LED Radioactive source Clock Minbias Muon system Director’s Review, BNL 9/28/06

Electronics (DAQ) Entire detector is readout on all physics triggers Each detector system at each site is readout independently (8 antineutrino streams and 9 muon streams. An event builder reassembles the streams Every e+, neutron or m+ will independently trigger a readout Primary Physics Triggers: Antineutrino Detector Esum: 0.7 MeV Emult: 10 PMTs Muon System Water Pool Water Tracker RPC Director’s Review, BNL 9/28/06

Calibration Load sensors, level sensors, thermometers, flow meters, mass flow meters LED Radioactive sources: 68Ge (1.022 MeV), 60Co (2.5 MeV), 252Cf 3-4 locations (with full z travel) Data (12B, neutrons, Michel electrons) Determine/maintain energy scale to 1% at 6 MeV throughout detector volume (=> neutron detection efficiency known to 0.2%). Director’s Review, BNL 9/28/06

More details in Bob McKeown’s talk Source Calibration More details in Bob McKeown’s talk Determination of attenuation length from 2 techniques: Neutron captures throughout volume relative to center (left) 60Co source in corner relative to center (right) Director’s Review, BNL 9/28/06

LED Calibration Calibration Goal: PMT gains Director’s Review, BNL 9/28/06

Detector Performance 224 PMTs with 12% effective photocathode coverage GEANT simulations Photoelectron yield vs. radius, no mineral oil Energy resolution 224 PMTs with 12% effective photocathode coverage ~100 photoelectron/MeV: 12.2%/E Director’s Review, BNL 9/28/06

Prototype Performance (1) 0.5 ton prototype at IHEP (currently unloaded liquid scintillator) 45 8” EMI 9350 PMTs with 14% effective photocathode coverage ~240 photoelectron/MeV and 9%/E Linearity Energy Resolution Director’s Review, BNL 9/28/06

Prototype Performance (2) Comparison of data and MC 0.5ton IHEP prototype L=1.0m, =0.9m 137Cs 137Cs 60Co Director’s Review, BNL 9/28/06

Conceptual design of the antineutrino detector is well advanced Summary Conceptual design of the antineutrino detector is well advanced Simulation of the detector response is well developed (Geant3), including several calibration studies (Geant4) Detailed engineering of the vessels, supports and calibration system is underway Prototype operational at IHEP, a 2nd prototype to be built at Aberdeen, studies underway of PMTs, electronics, calibration system and LS Director’s Review, BNL 9/28/06

Backup Director’s Review, BNL 9/28/06

Chooz Data Director’s Review, BNL 9/28/06