A three dimensional plasma simulation code applied to phase velocity prediction in a coupled cavity circuit

The problems encountered in the design of circuits for traveling wave devices are of sufficient difficulty that analytic solutions are not usually possible. Historically, resistive networks, electrolytic tanks, and analog computers have been used to simulate devices and thereby permit direct measurement of the field variations. With the advent of large digital computers, it has become possible to solve these problems in a much more general fashion by numerically integrating the fundamental differential equations over a discrete mesh. The recent development of numerical techniques to efficiently handle the massive data storage problem necessary to self-consistently solve Maxwell's equations with sources, combined with the continuing improvement in computer price/performance ratios, has led to the development of computer codes powerful enough to perform three-dimensional numerical experiments. Codes of this type have been used for a number of years in EMP calculations and in plasma physics. This paper will present the initial results of applying a three-dimensional plasma simulation code to microwave tube design problems; specifically, the cold testing of coupled-cavity to find phase/frequency characteristics.