Operating Experience with the Michigan State University Superconducting Cyclotron Cryogenic System

The MSU superconducting cyclotron cryogenic system has been operating for about one year and many cryogenic parameters have been measured. Data for cryostat cooldown, liquid helium consumption, liquid nitrogen consumption, cryostat warmup, and vacuum jacket pressure as a function of temperature have been taken. In addition, methods have been developed for handling of contaminants in the helium system (air), for filling liquid helium in the cryostat, and for various cryogenic failure modes. Finally, a leak detection method was developed that is applicable at liquid helium temperature and has been used to find ultra-small leaks in the cryostat. This method utilizes the density and viscosity variations of cold helium gas as a function of temperature and may ultimately provide three orders of magnitude sensitivity improvement beyond presently achieved room temperature leak rates.