Magnetic insulation in inhomogeneous external B-field

The experiment and the simple model presented in this paper show the difficulties of introducing large energy REB in region of large external Bz field. The comparison between the homogeneous B-field case (where Bz enhance the magnetic insulation) and the inhomogeneous case suggests that the problem can be solved by shaping properly the coaxial line. Choosing a coaxial line shape following the external field lines should probably enhance the magnetic insulation. Studies of new coaxial line shapes are presently in progress using numerical model taking into account the space charge effect.