Calibration, testing, commissioning and first data of ALFA at LHC

The ALFA (Absolute Luminosity For ATLAS) project aims at measuring luminosity of the LHC with high precision using pp elastic scattering under small angles. This will be done by moving an upper and a lower tracking detector inside Roman Pots very close to the beam. To align the upper and lower tracking detector a dedicated part overlaps and the alignment will be done with particles passing both the upper and the lower detector. The tracking detectors are made of scintillating square fibers read out by MultiAnode PhotoMutiplier Tubes, MAPMTs, with custom made electronics. The gain of the MAPMT channels has been equalized and the average light yield of scintillating fibers determined before installation in the LHC. Also reflections on the Roman Pot windows have been observed and the window has been blackened to reduce the effect. The ALFA detectors are currently being commissioned at ATLAS/LHC and the first particles have been observed in the detectors.