Prepulse influence on the electron beam pinch behavior in a large aspect ratio diode

It is well known that in REB Generators the prepulse causes great inconvenience and it is necessary to control its effects. In this paper we show the large aspect ratio diode behavior of a low impedance REB Generator (CHANTECLAIR, 2 ohms - 500 kV - 60 ns) with and without prepulse. With or without prepulse, the first noticeable fact to take into account consists of the basic mechanism which tends to pinch the beam. Wi th a 20 kV - 700 ns prepulse, the anode cathode gap is filled with a low density plasma which avoids the self focalisation observed without prepulse . It is possible to reach a narrow pinch on the anode by using some technological arrangements in this last case; the energy in the pinch is less than without prepulse.