INNOVATIVE ASPECTS OF THE CONTROLS FOR THE HELIUM CRYOPLANTS IN THE CERN SPS ACCELERATOR

For the coding of superconducting accelerating cavities in the CERN SP S, two identical helium refrigerators of 400 watt at 4.5 K have been r equired. The first one has been in operation since 1992 and the second one was commissioned at the beginning of 1994. Both refrigerators are equipped with an industrial process control system which allows fully automatic remote operation of the entire cryoplant from ambient to li quid helium temperatures. This achievement was obtained by combining t he suppliers knowledge of the refrigerators and the CERN operational e xperience with the capability of a modern control system. The logic of the cryoplant and its integration in the state of the art software co ncept, based on an object-oriented approach, are presented.