Calibration of photomultipliers for the Double Chooz experiment

The Double Chooz neutrino experiment consists of two similar detectors placed at ∝ 280 m and 1 km, respectively, from the Chooz power plant reactor cores. Each detector will contain about 400 photomultipliers in the inner part of the detector. The photomultipliers are 10 inch hemispherical optimized for low radioactive contamination (Hamamatsu R7081 MOD-ASSY). In order to calibrate these photomultipliers before installation a test facility was set up which allows the simultaneous calibration of up to 30 photomultipliers. In the tests we have examined the relative sensitivity, gain, noise-rate, time-response and stability in a standard procedure for 400 photomultipliers. Cross-check measurements of additional photomultipliers, which have been calibrated in an independent setup in Japan, are used to verify the quality of the calibration. This talk gives an overview on the test facility and the test results.