A Submicrosecond High-Current Electron Beam Source with an Explosive-Emission Cathode and an Auxiliary Discharge Initiated by a Pre-Pulse

摘要

In widely used electronic source circuits based on diodes with preliminary plasma filling, additional auxiliary discharge electrodes and separate generators are used to power the auxiliary discharge with its charging and triggering system. Technically, a simpler version is a circuit in which the potential auxiliary discharge electrode and the diode cathode are combined. In this case, two voltage pulses with a time delay are applied to the electrode in series. The first pulse (pre-pulse) is intended to initiate the emission on the cathode and the auxiliary discharge before the second primary pulse is applied. Under certain conditions, a pre-pulse leads to an increase in the electron beam current (double-pulse effect). An approach, in which double-pulse effect is used, has been studied with reference to a diode with a submicrosecond electron beam duration at a voltage level of 100-300 kV. The diode is composed of an explosion-emission blade cathode and a flat anode. As a generator, a low-resistance (wave resistance ~1 Ohm) air insulated Linear Transformer Driver (LTD) is used. The LTD stages are made of a capacitive energy storage of 80 nF with a charging voltage of 80 kV. An additional discharge circuit with its own 3.2 nF energy storage is used in each LTD stage to generate pre-pulse. The main and additional capacitive energy storages are charged from a common charging unit and commutated with a controlled time delay from a trigger source. The use of the pre-pulse has allowed a reduction in the diode resistance on the pulse front to a few Ohms. We have also managed to improve matching of the diode with the generator and increase the efficiency of the energy output from a low-resistance capacitive storage to the electron beam. The thermal imaging measurements of the electron beam profile showed that the presence of the pre-pulse does not disrupt the beam energy density distribution at the anode but increases the probability of beam pinching.