The revival role of nuclear emulsion detectors in the OPERA experiment

We discuss nuclear emulsion detectors, their history, types, scanning techniques as well as their revival key role in the OPERA experiment. Nuclear emulsion can be considered as an analog data storage device from which the automatic scanning system retrieves the data stored in it. The recent improvement of emulsion scanning techniques brings back the nuclear emulsion as one of the most important detectors among all other elementary particle detectors. OPERA uses the ECC technique used previously by the DONUT experiment. As in the OPERA experiment good modularity for a large apparatus is present, the existence of an automatic scanning system and the availability of fast data scan (Net Scan) are the required parameters, which can only be obtained by utilizing the ECC Nuclear emulsion technique. Therefore, the role of nuclear emulsion is very important in the OPERA experiment.