Mode competition and control in a 170~GHz gyrotron cavity for ECRH application

Article type: Research Article

Authors: Singh, R.K.^{a; b; *}

Affiliations: [a] Bharat Sanchar Nigam Ltd, Nodal Cell WiMAX, TPT Nagar, Ludhiana, Punjab, India | [b] Center of Research in Microwave Tubes, Electronics Engineering, Institute of Technology, Banaras Hindu University, Varanasi, India

Correspondence: [*] Corresponding author. E-mail: [email protected]

Abstract: The present paper is devoted to the study of mode competition and control in a 170 GHz gyrotron cavity for potential application in electron cyclotron resonance heating (ECRH) of plasmas. An extensive analysis has been carried out for coupling coefficient, start oscillation current, voltage depression, and limiting current for the candidate modes in the gyrotron cavity resonator. The study reveals that the main competing modes for TE_{28,8}^{-} come from TE_{25,9}^{+} and TE_{27,8}^{-}. The optimum beam position for TE_{28,8}^{ - } mode is found to be at 8.28 mm. To avoid excitation of competing modes, it has been found that slight increase in electron beam radius from 8.28 mm to 8.40 mm avoids the excitation of all the competing modes. Based on the considerations of coupling coefficient, start oscillation current, voltage depression, and limiting current; the TE_{28,8}^{-} mode is selected as the operating mode.

Keywords: Gyrotron, cavity design, mode competition

DOI: 10.3233/JAE-2012-1423

Journal: International Journal of Applied Electromagnetics and Mechanics, vol. 38, no. 4, pp. 195-202, 2012