A cooling unit operating in a magnetic field is provided. The cooling unit includes an encasement body having a non-electrically conductive composition and defining a first and second opposing planar surface. The cooling unit also includes a metal conduit disposed in the encasement body substantially parallel to the first surface. Additionally, the cooling unit also includes a series of metal fins disposed in the encasement body and extending from the conduit. In some configurations the fins can be substantially parallel to the first surface. Further, in some configurations, non-electrically conductive inserts having a thermal conductivity greater than a thermal conductivity of the encasement body can be disposed in a portion of the encasement body between one of the first and second surfaces and one or more of the metals fins.