Some problems in the design of nanosecond rise-time high voltage sources and electron guns



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Traditionally, electron beams have been driven by simple capacitive discharge schemes, wherein the cathode of an electron gun was connected in series with a charged capacitor by some type of high voltage switch. Techniques of this sort produced voltage rise times ranging from a few milliseconds to a few microseconds, which was usually quite acceptable for most purposes. Recent developments in laser technology, electron beam-plasma interactions, and so forth, has spurred interest in relatively simple, high voltage, nanosecond rise time electron beam devices. This thesis concerns itself with the problems encountered in the design and construction of fast rise time voltage sources, and the demands such rise times place on measurement circuits, timing circuits, and the electron gun itself. It is shown that charged delay line systems with coaxial spark gaps yield the best waveforms, and that some type of indirectly heated electron gun is best suited for nanosecond operation.