Studies of a Radially-Symmetric Transit Time Oscillator - The Radial Acceletron

摘要

The transit-time effect in a coaxial structure has been exploited to design and test a low impedance high power microwave source that uses no externally generated magnetic field and has no confining foil. An analytic model is used to extend a circuit model and estimate the values of the free parameters used in the circuit model and compares the analytical values to those obtained using two-dimensional (2D) particle-in-cell simulations. Further comparisons are made of the results of numerical solutions of the 1D circuit equations, 2D simulations, and initial experimental data. The Gemini pulser fitted with an extended Blumlein transmission line and located at the Air Force Research Laboratory/Phillips Research Site was used in the experiments to drive the Radial Acceletron. It is shown that the nonlinear relationship between voltage and current emission in a space-charge-limited diode drives an rf oscillation whose frequency is determined by the resonant characteristics of the annular diode cavity. The results from the 1D analysis and 2D particle-in-cell (PIC) simulation are shown to be in excellent agreement, and both are in agreement with the experimental data analyzed to-date.