| J.C. Barrière*, O. Cloué, B. Duboué, M. Fontaine, V. Gautard+, P. Graffin, C. Guyot, G. Jiolat,
P. Perrin, P. Ponsot, J.-P. Schuller, P. Schune, Y. Reinert
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ATLAS is a particle detector which is built at CERN-Geneva. It has to confirm the theory called “standard model”. In that way, one of the goals is to give a proof of the Higgs particle existence. The theory predicts this particle should decay in 4 muons which will be identified with a trajectory calculation. To achieve this, a set of 600 muon chambers (the muon spectrometer) will be installed around the interaction point. The muon spectrometer is quite 40m long and 22 m high. In order to get enough accuracy in the pulse determination, the geometry of muon spectrometer has to be known within 30 µm of resolution for translations and 200 µrad for rotations. The ranges of displacements are respectively +/- 5mm and 5 mrad.
Several alignment systems are running together to compute the shape of the spectrometer. We developed a low-cost 6D alignment sensor called praxial to meet these requirements. The praxial sensors are running by pair, each element facing to the other. Due to the 1000 pairs included in the alignment process combined with the accuracy required, a semi-automatic bench performs the calibration. The document will present the principle of the sensor and the hardware for both sensor and calibration bench. We will introduce the software, the absolute calibration procedure and conclude with the performances.
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