Operation of megavolt microsecond diode during injection of a relativistic electron beam into a magnetic mirror

Operation peculiarities of a high-voltage vacuum diode for a powerful accelerator of relativistic electron beam (REB) of microsecond duration for the case when the beam is injected through anode foil into longitudinal rising magnetic field are investigated. Total energy of the beam constituted approximately 100 kJ at pulse duration of approximately 4 μs. The magnetic field value rose from 0.5 Tl in the accelerator diode to 10 Tl in the magnetic mirror. The transport region was filled with neutral gas under the pressure from 10-5 to 1 Torr. It is shown that the diode operation mode during REB injection in the magnetic mirror varies considerably as compared with the case when the beam is accepted by a collector located immediately beyond the foil. It is ascertained that the beam electrons, reflected from the magnetic mirror and oscillating through the anode foil, are the reasons for the changes. It is detected that with an increase in the foil thickness the diode ''impedance collapse'' takes place. The beam propagation in the range of compression in the modes with partial current compensation and in its absence is investigated