Gd Liquid scintillator: completion of the R&D!Stability 0,1 % Gd in PXELENS R&D new metal -diketone molecule (MPIK)Stable: 0.1% Gd-Acac (few months) Baseline receipie ~80% mineral oil + ~20% PXE + Fluors + wavelenght shiftersIn-loaded scintillators (0.1 %, 5% loading) are counting @Gran SassoSpare stable receipies available (MPIK, INFN/LNGS)Gd-Acac moleculeCompletion of the R&D first half of 2004 Choice of the final scintillator Stability & Material compatibility Aging tests (MPIK, Saclay)3+Gd

Gd Liquid scintillator tests in Saclay Goal: 1/ Test the LONG term stability of the scintillator 2/ Test the material compatibility with acrylic, glue, ... Towards the desgin of the acrylic vessels Tight stainless steel boxes flushed with N2 20- 130cl quartz cuvettesAeging test scintillator temperature ~50 degrees Systematic periodic photospectrometer absorbance measurements

Acrylic vessels4m2m2.4m3.6m2.8mGamma catcherTargetThickness = 6mmFinal assembly (in several part)In Choozs siteAssembly in the manufacturerworkshop

Stress in acrylic vesselsSuspension:3 points at 120 degreesThickness: 6 mmEmpty weight:Target = 220kgGamma catcher = 470kg

Maximum stress: 12 MPaDAPNIA/SIS/LCAP - JMBTargetGamma catcher

Filling of vessels:

Dosing pums (diaphragm pumps or peristaltic pumps): accuracy ~1%

Pump + electronic flowmeter: accuracy ~0.5%

Weight & density measurementsDensity: accuracy 0.001 g/cm3 (can reach 0.0001 g/cm3)Weigth: accuracy volume ~0.1%

Full detector simulationPCC & APC, Kurchatov

Parameters used for the simulationReactor thermal power: 8.4 GWNear detector distance: 150 meters Volume N & F: 12.67 m3Far detector distance: 1050 meters with PXE => 12.5 tonsNear detector efficiency: 32 % 50 % dead time x 80 % global load factor x 80 % detectionFar detector efficiency: 64 %No dead time x 80 % global load factor x 80 % detection

Standard systematic errors:absoluterelativebackgrounds1 par fitorwith

Sensitivity at 90% C.L. if sin2(213)=0 versus integrated luminosity in RNU abs=2% rel=0.6% shape=2% b2b=1%Reactor 1 (2 RNU) Reactor 2 (40 RNU)New target compositionincreases luminosity by 30 %1 RNU = 200 t.GW.y

Summary & outlook @Double-CHOOZSupport for the EDF power company to do a 2nd experiment @CHOOZDouble-CHOOZ sensitivity: sin2(213)