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Radial Acceletron, A New Low Impedance HPM Source

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Final rept. Nov 1991-Oct 1992

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This report explores and analyzes using transit-time effects in a coaxial geometry to develop a low-impedance high power microwave HPM source that uses no external magnetic field and no confining foils. This source works in the 1-20 GHz range and has a power output of no less than 1 GW. The input is a low-voltage dc pulse of only 350 kV or less with a flat top of approximately 200 ns. The dc pulse is launched into a coaxial structure comprised of the diode, the oscillator, and the buncher. Strong impedance mismatch between the diode section and the body of the device provides enough reflection to have a well defined coaxial cavity of high Q to support cavity characteristic modes. Electrons emitted from the inner conductor of the structure accelerate toward the anode interacting with a selected characteristic mode of the structure, usually losing kinetic energy to the mode, until the RF fields are strong enough to optimize, thus leading to saturation. The source offers significant improvements in power, repetition rate, size, and efficiency because of the coaxial structure. The diode impedance may be reduced to a few ohms thus allowing larger input and output powers. With no foils to erode, the only thing limiting the repetition rate is the vacuum ability and, with no external magnetic field required, the device is simple, lightweight, and inexpensive. Because of the strong bunching, the efficiency is high and, as with all transit- time oscillators, the signal is stable and monochromatic. The device may be used as a buncher or as an oscillator.

Subject Categories:

  • Particle Accelerators
  • Radiofrequency Wave Propagation

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