MULTI-TESLA PERMANENT-MAGNET FIELD SOURCES

Both cylindrical (''magic ring'') and spherical (''magic sphere'') dip olar Permanent magnet field sources are capable of providing arbitrari ly high fields in their interior cavities. However, since the obtainab le field increases only logarithmically with the structural radius, fi elds above about 2.5 T necessitate excessively massive and costly stru ctures if working volumes of more than a few cm3 are desired. The pres ent work shows how for some cavity shapes the structures can be modifi ed to produce fields up to 4.0 T with only about one fifth the mass an d bulk of the conventional structures. Possible applications which wou ld be impractical with the unmodified field sources are cited.