Fig. 5. The overall efficiency versus input power for the spherical gyrocon. aberration and produces a much tighter beam at the output cavity. This allows improved efficiency. Because the angular bunching is as tight as 20°, output-cavity electronic efficiency can approach 100%. High-Q cavities produce a narrow bandwidth and should produce a very clean signal. 2. SIMULATION RESULTS Gyrocons are analyzed with two computer codes developed at LASL. The first, gyrol, follows the electrons through the deflection, drift, bender, and output regions of the radial-style gyrocon. The efficiency is calculated by the change in total kinetic energy as the electrons traverse the output cavity. Reference (3) presents a detailed description of the equations and assumptions. The second, gyros, has the spherical output cavity fields instead of the coaxial cylinder output fields. All other subroutines are the same. Both codes include large signal effects, relativity, and space charge. The major assumptions in these codes are the neglect of the aperture effects in the deflection and output cavities, and the neglect of image charges in the space-charge routines. The aperture effects are larger at the relatively high frequency of 2.45 GHz that has been chosen for the Solar Power Satellite. We have made a limited parameter search of spherical gyrocon characteristics using the LASL code. At 2.45 GHz. we find increasing overall efficiency with increasing input power (Figure 5). The microperveance for these runs is about 0.1. This makes the gyrocon a low perveance device. The efficiency curve is roughly logarithmic, and electronic efficiencies of over 97% are predicted for the higher input powers. Output-cavity wall losses at 1.8-MW input average about 350 W/cm2. Total output-cavity losses are about 172 kW. Figures 6, 7, and 8 show various projections of the path formed by the passage of a single layer of electrons through
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