Cold Analysis for Dispersion, Attenuation and RF Efficiency Characteristics of a Gyrotron Cavity

Authors: R. K. Singh

Abstract:

In the present paper, a gyrotron cavity is analyzed in the absence of electron beam for dispersion, attenuation and RF efficiency. For all these characteristics, azimuthally symmetric TE0n modes have been considered. The attenuation characteristics for TE0n modes indicated decrease in attenuation constant as the frequency is increased. Interestingly, the lowest order TE01 mode resulted in lowest attenuation. Further, three different cavity wall materials have been selected for attenuation characteristics. The cavity made of material with higher conductivity resulted in lower attenuation. The effect of material electrical conductivity on the RF efficiency has also been observed and has been found that the RF efficiency rapidly decreases as the electrical conductivity of the cavity material decreases. The RF efficiency rapidly decreases with increasing diffractive quality factor. The ohmic loss variation as a function of frequency of operation for three different cavities made of copper, aluminum and nickel has been observed. The ohmic losses are lowest for the copper cavity and hence the highest RF efficiency.

Keywords: Gyrotron, dispersion, attenuation, quality factor.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1088900

References:

[1] O.P. Gandhi, “Microwave engineering and applications,” New York: Pergamon Press, 1981.
[2] M. V. Kartikeyan, E. Borie, and M. K. A. Thumm, “Gyrotrons: High-power microwave and millimeter wave technology,” Germany: Springer, 2004.
[3] K. J. Kim and M. E. Read, “Design considerations for a megawatt CW gyrotrons,” Int. J Electronics, vol. 51, pp. 427-432, 1981.
[4] R. A. Correa, B. Levush, and T. M. Antonsen, “High efficiency cavity design of a 170 GHz gyrotron for fusion applications,” Phys Plasmas, vol. 4, pp. 209-216, 1997.
[5] B. Piosczyk, O. Braz, G. Dammertz, C. T. Latrou, S. Illy, M. Kuntze, G. Michel, and M. Thumm, “165GHz, 1.5MW-coaxial cavity gyrotron with depressed collector,” IEEE Trans. on Plasma Sci., vol. 27, pp. 484-489, 1999.
[6] K. E. Kreischer, T. Kimura, B. G. Danly, and R. J. Temkin, “High power operation of a 170 GHz megawatt gyrotron,” Phys. Plasmas, vol. 4, pp. 1907-1914, 1997.
[7] G. G. Denisov, V. L. Bratman, A. D. R. Phelps, and S. V. Samsonov, “Gyro-TWT with a helical operating waveguide: New possibilities to enhance efficiency and frequency bandwidth,” IEEE Trans. Plasma Sci., vol. 26, pp. 508-518, 1998.
[8] R.K. Singh, “Mode competition and control in a 170 GHz gyrotron cavity for ECRH application,” Int. J. Applied Electromagnetics and Mechanics, vol. 38, no. 4/2012, pp. 195-202, 2012.
[9] B. N. Basu, “Electromagnetic Theory and applications in beam-wave electronics,” Singapore: World Scientific, 1996.
[10] K. Felch, R. Bier, L. J. Craig, H. Huey, L. Ives, H. Jory, N. Lopez, and S. Spang, “CW operation of a 140 GHz gyrotron,” Int. J Electronics, vol. 61, pp. 701-714, 1986.
[11] G. S. Nusinovich, M. E. Read, O. Dumbrajs, and K. E. Kreischer, “Theory of gyrotrons with coaxial resonators,” IEEE Trans. Electron. Devices, vol. 41, pp. 433-438, 1994.
[12] O. Dumbrajs, and G. I. Zaginaylov, “Ohmic Losses in Coaxial Gyrotron Cavities with Corrugated insert,” IEEE Trans. Plasma Sci., vol. 32, pp.861-866, 2004.
[13] Z. C. Loannidis, O. Dumbrajs, and I. G. Tigelis, “Eigenvalues and ohmic losses in coaxial gyrotron cavity,” IEEE Trans. Plasma Sci., vol. 34, pp. 1516-1522, 2006.
[14] MATLAB: The Language of Technical Computing, User’s Guide, Natick MA: The MathWorks (www.mathworks.com).