Power electron beam front shortening in magnetically insulated transmission line with inner coaxial dielectric insert

The starting point for this investigation is a suggestion that it is possible to get a clearly defined shock electromagnetic wave in a quite short modified magnetically insulated transmission line (MITL). The line modification resides in an inner coaxial dielectric insert. One may consider the insert as a distributed matched spark-gap. The parameters of the high voltage pulse supplying at the line input are as follows: 1.5 MV, 20-30 kA, 90 ns, front duration /spl sim/30 ns. A current pulse with a front duration less than 1 ns has been observed at the line output. The output current has ranged up to about 10-12 kA. Efficiency of the sharp front formation grows owing to its dependence on the speed of the flashover front propagation. So, an estimation of this dependence is a step of great importance in solution of the problem. The flashover front speed has been estimated on physical grounds which can be derived from experimental data for the early phase of dielectric surface flashover in vacuum.