The Emulsion Scanning System of the OPERA experiment

The OPERA experiment has for goal the direct detection of !μ ! !! oscilla- tion, using an hybrid apparatus composed of electronic detectors and nuclear photographic emulsions. A charged particle crossing an emulsion layer ion- izes the medium along its path leaving a latent image which leads, after de- velopment, to a sequence of aligned grains. Nuclear emulsions are analyzed by means of optical microscopes to reconstruct the 3D particle tracks. The OPERA collaboration has developed a dedicated system to scan a large num- ber of emulsions (surface of about 1000 m2). The achieved resolution is "1 μm and "1 mrad allowing to observe directly the short-lived " particles pro- duced in !!CC interactions.