Computer simulations of a third-harmonic system of 1.8-MW input show that a beam deflection of 25° still produces an electronic efficiency over 95% in such an output cavity. However, over three times the drive power is required to obtain the greater deflection. Output-cavity losses roughly double with the larger cavity. The Q rises by 26%, but the overall efficiency drops to about 68%. Frequency multiplication in the output cavity should also be possible with a triro- tron. The main requirement is a reasonably well-bunched electron beam. If the actual beam width is A degrees and the order of multiplication is m, then the bunching should satisfy mA s ±60° for optimal efficiency. The trirotron should avoid the problems associated with the larger deflection angles needed in spherical gyrocon multipliers. There may also be an advantage to operating the cathode in such a system in a similar multiplier mode. 4. CONCLUSIONS It appears feasible to build very high power, high efficiency gyrocons for S-band operations. This can be done by eliminating the bender and its consequent beam aberrations. The result is a narrow bandwidth device that should produce good rejection of unwanted noise. Unit power levels seem to be around 2 MW at 2.45 GHz for overall efficiencies over 80%. Higher powers produce even higher efficiencies. Gains are quite low compared to klystrons, but may be improved by newer beamdeflection systems. Cooling requirements appear to be challenging, but are within ranges accepted as possible with heat pipes. Frequency-multiplier operation is possible, but would not be the preferred mode in a spherical gyrocon. Further extension of the gyrocon concept into trirotrons rrtay produce the advantages of gyrocons without the above problem areas. Acknowledgment — The authors appreciate the efforts of Barbara E. Canada in making many of the computer simulations for this paper. REFERENCES 1. I. Kaufman and G. Oltman, Harmonic Generation by Electron Beam Pattern Motion — The Bermut- ron, IEEE Trans. Electron Devices, ED-12, 31-39, 1965. 2. G.I. Budker, M.M. Karliner, I.G. Makarov, S.N. Morosov, O.A. Nezhevenko, G.N. Ostreiko and I.A. Schekhtman, The Gyrocon — An Efficient Relativistic High-Power VHF Generator, Particle Accelerators, 10, 41-59. 1979. 3. P.J. Tallerico and J.E. Rankin, The Gyrocon: A High-Efficiency, High-Power Microwave Amplifier, IEEE Trans. Electron Devices. ED-26(10), 1559-1566, 1979. 4. B.W. Montague, Radio-Frequency Separators. Chapt, 3.7, in Linear Accelerators by P.M. Lapostolle and A.L. Septier, North Holland Publishing Co.. Amsterdam, 1970. 5. T. Wessel-Berg, A New Concept for Generation of Multi-Megawatt Power Approaching Hundred Percent Conversion Efficiency, Technical Digest, International Electron Devices Meeting, Washington, DC, 238-241, 1977. 6. K. Halbach and R. Holsinger, superfish — A Computer Program for Evaluation of rf cavities with Cylindrical Symmetry, Particle Accelerators, 7, 213-222, 1976. 7. E.J. Nalos. High Efficiency SPS Klystron Design, unpublished paper presented at the NASA Solar Power Satellite Workshop on Microwave Power Transmission and Reception. Jan. 15-18, 1980 (Houston). 8. J.V. Lebacqz, A.J. Dudas and W.R. Fowkes, The Trirotron, IEEE Trans. Nad. Sei., NS-26, 3891— 3893, 1979.
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