volume | PIER Journals

Abstract

This paper presents the design and fabrication of HE₁₁ miter bend along with a TM₁₁ to HE₁₁ mode converter and corrugated up-taper, which are the integral parts of a transmission line system (TLS) that carries 200 kW microwave power at 42 GHz from Gyrotron to plasma or calorimetric dummy load. It has a hybrid (HE₁₁) mode. The HE₁₁ mode transmission loss in miter bend is derived using mode-matching techniques and gap loss theory. The gap length (L) in a waveguide of diameter (D = 2a) at a wavelength (λ) for the predicted loss (D ≥ λ) is approximately 1.7[Lλ/2a²]^3/2 dB. The HE₁₁ miter bend design incorporates a demountable cooling assembly with a flat mirror. The design and optimization of the proposed miter bend were carried out using CST-microwave studio software. Finally, HE₁₁ miter bend was fabricated along with integrated assembly. The proposed HE₁₁ miter bend with mode converter and corrugated up-taper gives the transmission efficiency of 95.64%.

1. Shapiro, M. A. and S. N. Vlasov, "Study of combined transmission line for high power generates by gyrotron in the mm wavelength range," International Journal of Electronics, Vol. 72, 1127-1133, 1992.
doi:10.1080/00207219208925638 Google Scholar

2. Singha, U., N. Kumara, H. Khatuna, N. Kumara, V. Yadava, A. Kumara, M. Sharmaa, M. Alariaa, A. Beraa, P. K. Jain, and A. K. Sinh, "Design of 42 GHz gyrotron for Indian fusion tokamak system," Fusion Engineering and Design, Vol. 88, No. 11, 2898-2906, November 2013.
doi:10.1016/j.fusengdes.2013.06.001 Google Scholar

3. Singh, U., U. Goswami, H. Khatun, N. Kumar, N. Shekhawat, A. Kumar, V. Yadav, M. Sharma, A. Mishra, S. Sharma, M. Alaria, A. Bera, R. Rao, and A. Sinha, "Design of 42 GHz, 200 kW gyrotro," IEEE International Vacuum Electronics Conference, California, USA, 18-20, May 2010. Google Scholar

4. Thumm, M., "High-power millimetre-wave mode converters in overmoded circular waveguides using periodic wall perturbations," International Journal of Electronics, Vol. 57, No. 6, 1225-1246, 1984.
doi:10.1080/00207218408938998 Google Scholar

5. Thumm, M., "High power mode conversion for linearly polarized HE₁₁ hybrid mode output," International Journal of Electronics Theoretical and Experimental, Vol. 61, No. 6, 1135-1153, 1986.
doi:10.1080/00207218608920944 Google Scholar

6. Patel, A., R. Goswami, and P. Bhatt, "TM₁₁ to HE₁₁ mode converter in overmoded circular corrugated waveguide," IET Antenna and Microwave Propagation, Vol. 3, No. 8, 1202-1207, 2019.
doi:10.1049/iet-map.2018.5627 Google Scholar

7. Nanni, E. A., S. K. Jawla, M. A. Shapiro, P. P. Woskov, and R. J. Temkin, "Low-loss transmission lines for high-power terahertz radiation," Journal of Infrared, Millimeter and Terahertz Waves, Vol. 33, No. 7, 695-714, July 2012.
doi:10.1007/s10762-012-9870-5 Google Scholar

8. Thumm, M., V. Erckmann, G. Janzen, W. Kasparek, G. Muller, P. G. Schuller, and R. Wilhelm, "Generation of the gaussian like HE₁₁ mode from gyrotron TE_0n mode mixtures at 70GHz," International Journal of Infrared and Millimeter Waves, Vol. 6, No. 6, 459-470, 1985.
doi:10.1007/BF01010037 Google Scholar

9. Tax, D. S., Mode conversion losses in overmoded millimeter wave transmission lines, Massachusetts Institute of Technology, September 2008.

10. Vikharev, A. A., G. G. Denisov, S. V. Kuzikov, and D. I. Sobolev, "New TE₀₁ waveguide bends," Journal of Infrared, Millimeter and Terahertz Waves, Vol. 30, No. 6, 556-565, 2009.
doi:10.1007/s10762-009-9478-6 Google Scholar

11. Doane, J. L. and C. P. Moeller, "HE₁₁ miter bends and gaps in circular corrugated waveguide," International Journal of Electronics, Vol. 77, No. 4, 489-509, 1994.
doi:10.1080/00207219408926081 Google Scholar

12. Shapiro, M. A. and R. J. Temkin, "High power miter-bend for the next linear collider," Proceedings of the 1999 Particle Accelerator Conference (Cat. No. 99CH36366), Vol. 2, 836-838, IEEE, New York, USA, March 1999. Google Scholar

13. Kowalski, E. J., Miter bend loss and higher order mode content measurements in overmoded millimeter-wave transmission lines, Ph.D. diss., Massachusetts Institute of Technology, 2010.

14. Vaganov, R. B., "Measurements of losses of certain quasi-optical waveguide elements," Radio Engineering and Electronic Physics, Vol. 8, 1228-1231, 1963. Google Scholar

15. Sporleder, F., "A compact 90^◦ corner with expanded diameter and elliptic mirror for circular waveguide," International Conference on Millimetric Waveguide Systems , 68-71, London (I.E.E. Conference Publication No. 146), 1976. Google Scholar

16. Vlasov, S. N. and M. A. Shapiro, "Optimization of a miter bend for oversized waveguide with corrugated walls," Radio Engineering and Electronic Physics, Vol. 36, 2322-2326 , 1991, (in Russian issue). Google Scholar

17. Graubner, T., "Design and measurements of HE₁₁ + HE₁₂ mode converters," 17th International Conference on Infrared and Millimeter Waves, Vol. 1929, International Society for Optics and Photonics, Chengdu, China, 1992. Google Scholar

18. Patel, A., P. Bhatt, K. K. Mahant, A. D. Vala, K. Sathyanarayan, S. V. Kulkarni, and D. Rathi, "Oversized circular corrugated waveguides operated at 42 GHz for ECRH application," Progress In Electromagnetics Research M, Vol. 88, 73-82, 2020.
doi:10.2528/PIERM19102302 Google Scholar

19. Denison, D. R., Gyrotron mode converter mirror shaping based on phase retrieval from intensity measurement, Massachusetts Institute of Technology, June 1999.

20. Sathyanarayana, K., S. V. Kulkarni, A. Patel, P. Bhatt, A. Vala, H. Mewada, and K. Mahant, "Sensitivity analysis on predicted microwave performance of mode converters with geometrical tolerances for 42-GHz transmission line components," Fusion Science and Technology, Vol. 75, No. 3, 234-243, April 2019.
doi:10.1080/15361055.2018.1557984 Google Scholar

Dr. Amit Patel

Dr. Pujita Bhatt

Dr. Keyur Mahant

Dr. Alpesh D. Vala

Dr. Jitendra P. Chaudhari

Dr. Hiren Mewada

Dr. Krishnamachari Sathyanarayan