Development of Magy Code for Modeling of Gyrotrons with Coaxial Cavities

Summary form only given. Millimeter-wave gyrotrons with coaxial cavities are very promising devices since they have a superior mode selectivity with respect to cylindrical gyrotrons. The design of high power gyrotrons is greatly aided by numerical simulation. This is particularly important when mode competition is being considered. The design code MAGY (MAryland GYrotron) has been used in the past by the US vacuum electronic industry to design high power gyrotrons for fusion applications. We report here on development MAGY making it suitable for accurate and efficient simulation of gyrotrons with coaxial cavities. The MAGY model includes a self-consistent, non-linear solution of the three-dimensional equations of motion of electrons and the solution of the time-dependent field equations. The model differs from the conventional particle in cell (PIC) approach in that the field spectrum is assumed to consist of a carrier frequency and its harmonics with slowly varying envelopes. The electromagnetic field model was originally applied to devices where the local cross-section is circular. In the present work we have extended the model to be capable of treating coaxial structures. The modified code has been validated by comparison of simulation results with the results of experimental measurements presented in [C.T. Iatrou et al., IEEE Trans. on Plasma Science, vol. 25, no. 3, p. 470-9 (1997)]. The calculated dependence of the output power on beam voltage agrees with the results of measurements. The next step in code development is to develop a model for the simulation of the effects of a corrugated inner conductor.