Operating Experience with a Superconducting Magnet in an Accelerator Experiment

A superconducting solenoid was incorporated into a physics experiment at the LRL 184-inch cyclotron. The magnet was kept superconducting for the entire run of 5½ months. The solenoid has a 4-1/4 in. diameter warm bore and an overall length of 3-1/2 ft. The field intensity is 60 kG. The proposed conventional solenoid which it displaced was 11 ft long. Buried in a steel and concrete shielding wall, the solenoid was the least accessible of all components in the experiment. This condition imposed great emphasis on the reliability of the coil and cryostat structure. The cryostat was cooled by direct evaporation of liquid helium (LHe) and liquid nitrogen (LN). The LHe supply Dewar and vacuum pump were located 25 ft from the magnet in a region accessible only with accelerator beam off. Liquidhelium automatic fill controls and LN supply Dewars were located 40 ft from the magnet in a region adjacent to the experiment control room. The solenoid was energized continuously by the power supply--no persistent mode switch was provided.