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This paper investigates the antenna waveguide (launcher), the main component of the quasi-optical mode converter of a 2-MW 170-GHz T[E.sub.34,19] coaxial cavity gyrotron, which is under development within the European Union. For coaxial gyrotrons operating in very high-order cavity modes like the T[E.sub.34,19], due to the ratio of the caustic to cavity radius of 0.323, the transformation of the high-order cavity mode into a nearly Gaussian distribution cannot be done as good as for gyrotron modes where the ratio of caustic to cavity radius is approximately 0.5. The simulation results for the T[E.sub.34,19] mode show that the average and peak values of the power density at the edges of the cuts of a conventional dimpled-wall launcher are approximately 32.3 W/[cm.sup.2] and 63.8, respectively, which will produce diffraction losses and reflection of power from the cuts. This paper reports on an advanced launcher for which average and peak values of power density of 1.9 and 5.4 W/c[m.sup.2] at the edges of the cuts are achieved, and a well-focused field at the aperture with a scalar Gaussian mode content of 94.8% is obtained. Index Terms--Coupled-mode theory, gyrotron, quasi-optical (QO) mode converter, wall perturbations.

This paper deals with the effect of parallel (rather than series) connection of the drive coils on the input voltage requirements, as well as on the energy utilization, of hypervelocity linear induction coil launchers fed by flywheel motor/generator sets. All of our previously published studies, 1987 to date, have dealt with series (rather than parallel) connected drive coils, which led to high input phase voltages and relatively low phase currents. In practice, the phase voltage per coil length should be kept below 30 kV/cm, the breakdown voltage of air. Furthermore, at any given time during the acceleration, the moving projectile (surrounded by a cylindrical sleeve) occupies only a portion of a barrel section length. When a parallel connection is used, the currents in the drive coils around the sleeve will be higher than the currents in the other coils in that section. That results in a greater accelerating force than in the series case, which leads to improved energy utilization. The simulation code used in our previously published work to predict the performance of a sectionalized, 3 kg projectile machine, was modified to obtain parallel-connection results for a similar machine. The paper describes the new drive-coil/pulse-generator configuration, explains the mathematical model, and provides graphs to compare the new results with those obtained previously with the series configuration. Index Terms--Electromagnetic launchers, hypervelocity launchers, induction coil launchers.

In this paper, the structure of a 'rail-coil' hybrid electromagnetic launcher is described, a force acting on launching body is calculated, the expresses of the projectile acceleration, velocity, and distance are deduced, and the advantages of this hybrid electromagnetic launcher are discussed. Index Terms--Coil launcher, 'rail-coil' hybrid electromagnetic launcher, rail launcher.