Abstract
This work reports calculations and measurements on mode converters for the transformation of TEOn gyrotron mode mixtures (primarily TEO2) into the linearly polarized HE11 hybrid mode at 70 GHz. This mode is ideal for quasi-optical launching systems for ECRH of plasmas. Mode transducers with axisymmetric radius perturbations convert the gyrotron TEOn mode composition into the TEO1 mode. Proper matching of the phase differences between the various modes and of the perturbation amplitudes of the several converter sections is required. The TEO1 wave is used for long-distance transmission through smooth-walled overmoded waveguides. A mode converter with constant diameter and periodically perturbed curvature transfers the unpolarized TEO1 mode into the polarized TE11 wave. The experimentally determined ΣTEOn-to-TEO1 conversion efficiency is (98.5±1)% (99% predicted) while the TEO1-to-TE11 transformer has a (94±2)% efficiency (93% theoretically); ohmic losses are included. The “Gaussian-like” HE11 mode with axisymmetric power distribution and almost no cross polarization is produced in a circumferentially corrugated TE11-to-HE11 mode transducer with a measured conversion efficiency of (98.3±1.5)% (98.5% predicted). The overall efficiency of the complete mode converter system in the desired mode was determined to be (91±2.5)%. High-power operation (200kW, 100ms) has been successfully demonstrated.
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Wilhelm, R., V. Erckmann, G. Janzen, W. Kasparek, G. Müller, E. Räuchle, P.G. Schüller, K. Schwörer, M. Thumm, W VII-A Team, Plasma Physics and Controlled Fusion,26 (1984) 1433.
England, A.C., IEEE Trans.Plasma Science,PS-12 (1984) 124.
Thumm, M., Proc. 1st EURATOM Workshop on High Power Microwave Transmission Systems for ECRH at 28 GHz and 60 GHz, Culham (1982), 61.
Erckmann, V., G. Janzen, G. Müller, P.G. Schüller, M. Thumm, R. Wilhelm, Proc. 5th Top. Conf. on RF Plasma Heating, Madison (1983), 209.
Thumm, M., G. Janzen, G. Müller, P.G. Schüller, R. Wilhelm, V. Erckmann, Proc. 3rd ECRH Transmission System Workshop, U.S. DOE, Germantown (1983), 220.
Thumm, W., G. Janzen, G. Müller, P.G. Schüller, R. Wilhelm, V. Erckmann, Conf.Digest 8th Int.Conf. on Infrared and Millimeter Waves, Miami Beach (1983), TH4.7.
Thumm, M., V. Erckmann, G. Janzen, G. Müller, P.G. Schüller, R. Wilhelm, Proc. 4th Int. Symp. on Heating in Toroidal Plasmas, Rome (1984), Vol. II, 1461.
Thumm, M., Int. J. Electronics,57 (1984) 1225.
Clarricoats, P.J.B., A.D. Olver: “Corrugated Horns For Microwave Antennas”, P. Peregrinus, Hitchin, 1984.
Kovalev, N.F., I.M. Orlowa, M.I. Petelin, Radio Phys. Quant. Electronics,11 (1969) 449.
Moeller, C., Int. J. Electronics,53 (1982) 587.
Janzen, G., H. Stickel, Int. J. Infrared and Millimeter Waves,5 (1984) 1405.
Doane, J.L., Int. J. Electronics,53 (1982) 573.
Beyer, J.B., K. Audenaerde, J.E. Scharer, IEEE Trans. Plasma Science,PS-11 (1983) 255.
Thumm, M., Conf. Digest 9th Int. Conf. on Infrared and Millimeter Waves, Takarazuka, Japan, (1984), 524.
Kühn, E., V. Hombach, IEE Conf. Publ.,219 (ICAP 83), 1983, Part 1, 127.
Erckmann, V., G. Janzen, W. Kasparek, G. Müller, P.G. Schüller, M. Thumm, R. Wilhelm, Proc. 13th Symp. on Fusion Technology (SOFT), Varese (1984), Vol. I, 553.
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Thumm, M., Erckmann, V., Janzen, G. et al. Generation of the Gaussian-like HE11 mode from gyrotron TEOn mode mixtures at 70 GHz. Int J Infrared Milli Waves 6, 459–470 (1985). https://doi.org/10.1007/BF01010037
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DOI: https://doi.org/10.1007/BF01010037