Comparison of theory and simulation for a radially symmetric transit-time oscillator

Summary form only given, as follows. The transit-time effect in a coaxial structure has been used by Arman (1996) to design low impedance high power microwave devices that use no externally-generated magnetic fields and have no confining foils. Luginsland et al. (1997) have developed simple one-dimensional (1-D) non-linear circuit equations that are solved numerically to estimate key device characteristics. This paper extends this approach to analytically estimate the values of the free parameters used in the circuit equations, compares the analytical values to similar values derived from two-dimensional (2-D) particle-in-cell simulations, and compares the results of numerical solutions of the 1-D circuit equations and 2-D simulations. It is shown that the non-linear 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; damping and electromagnetic field saturation results from a combination of transit time effects and electron bunching due to the non-linear electron emission characteristics of the space charge limited diode. The results from the 1-D analysis and 2-D particle-in-cell simulation are shown to be in excellent agreement.