Experimental evaluation of 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 a low impedance high power microwave device that uses no externally generated magnetic fields and has no confining foils. Luginsland et al. (1997) have developed simple one-dimensional (1D) non-linear circuit equations that are solved numerically to estimate key device characteristics. A prototype device based on the design by Arman was fabricated and tested. Initial results differed significantly from predictions derived both from 1D theory and initial particle-in-cell (PIC) simulations; no RF was generated. After modification of the design simulations to more accurately account for boundary conditions and an overestimation of diode current, and minor modifications to the prototype hardware design, the device was re-tested. Simulation predictions of the key 1D parameters differed significantly from measured values, and test results were not well-predicted by either the simulation estimates or the measured values of the 1D parameters. RF output generally corresponded with the expected results: the relative RF power generated in the different system configurations varied as predicted by simulation, although RF growth rates and absolute power levels differed from simulation by a factor of two to three. This presentation presents the results of the experimental evaluations, and compares the experimental data with analytical and simulation predictions.