Rare earth-cobalt magnet assemblies for charged particle beams

Recent designs of rare earth-cobalt magnet assemblies utilizing permanent magnets by themselves ('pure' REC devices) and permanent magnets in combination with high permeability material (REC 'plus iron' devices) have been studied and developed. There are four different basic types of magnets which have or are being built for charged particle beam focusing and bending applications. These four different types of magnet assemblies are (1) multipoles such as quadrupoles and sextupoles for beam focusing/separation applications, (2) solenoids for beam focusing and laser light polarization, (3) dipoles for beam bending, and (4) wigglers for electron beam bending/lasing applications. These applications require very accurate field distributions, i.e., typical field errors the order of 1 part in 102 or 103. In a magnet assembly where the field distribution is determined by the position and properties of the magnet pieces alone without any high permeability material, this level of accuracy is very difficult to achieve. Therefore, it has been necessary to develop methods and techniques which allow the field errors to be reduced by adjusting or 'tuning' the assemblies to the required degree of precision. (Author)