An iterative approach for the 3-D representation of focusing axisymmetric magnetic fields in TWT collectors

In this paper, a new efficient iterative procedure is presented for the computation of the equivalent ideal loop representation of the focusing axisymmetric magnetic field inside traveling wave tube (TWT) collectors. In the procedure, local and global inverse problems are iteratively solved in sequence until a target precision in the representation is achieved. The adopted approach allows us to obtain a very accurate representation of complicated shape fields by using only a few coils. In this way, electron trajectories inside TWT collectors can be precisely determined with reduced computational effort. In order to illustrate the advantages of the procedure, several examples of comparisons between computed and measured magnetic field profiles are also given