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The LMPV is a mercury-cathode, triggered, closing switch which employs a small area mercury pool and a cooled (-30 C) condensing surface to maintain the conditions for vacuum arc operation. These conditions result in high-voltage capability, fast recovery and high current operation with negligible cathode wear. Therefore, the LMPV was considered to have potential as a high average power closing switch for modulator applications. An LMPV closing switch (LMPVCS) was built at Hughes Research Laboratories and evaluated at ERADCOM at voltages up to 150 kV, currents up to 8 kA peak and 7.5 A average, pulse lengths up to 50 microseconds, and repetition rates up to 250 Hz. The device failed as a result of excessive anode dissipation caused by a long anode fall time on the order of 5 microseconds. Subsequent experimentation has indicated that the fall time is reduced at increased mercury vapor pressures, however, experiments are required to define the relation between the fall time and voltage hold-off capability. (Author)

The objectives of the current program are (1) to continue the development of the plasma cathode electron gun to optimize the performance characteristics and to improve reliability, and (2) to investigate the possibility of an 'integral plasma gun laser' in which a low pressure laser may be incorporated into the plasma cathode electron gun and eliminate the need for a foil window. This report describes the recent experimental results on the 4 cm x 40 cm electron gun. A lower pressure version of the plasma cathode electron gun, which was built for another contract-funded program, is described to show an important possible extended use of this kind of gun. A summary of the conclusions of the results from this reporting period is given., See also report dated Jun 1975, ADA012529.