Lawrence Berkeley National Laboratory

Small 4 K coolers are used to cool superconducting magnets. These coolers are usually used with high temperature suerconductor (HTS) leads. In most cases, magnet is shielded with iron or active shield coils. Thus the field at the cooler is low. There are instances when the cooler must be in a magnetic field. Gifford McMahon (GM) coolers or pulse tube coolers are commercially available to cool the magnets. This paper will discuss how the two types of coolers are affected by the stray magnetic field. Strategies for using coolers on magnets that generate stray magnetic fields are discussed.