Effect of electron-cyclotron resonance plasma heating conditions on the low-frequency modulation of the gyrotron power a
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Effect of Electron-Cyclotron Resonance Plasma Heating Conditions on the Low-Frequency Modulation of the Gyrotron Power at the L-2M Stellarator G. M. Batanova, V. D. Borzosekova, L. V. Kolika, E. M. Konchekova, b, D. V. Malakhova, b, c, M. I. Petelind, A. E. Petrova, b, K. A. Sarksyana, N. N. Skvortsovaa, e, f, V. D. Stepakhina, b, and N. K. Kharcheva a
Prokhorov General Physics Institute, Russian Academy of Sciences, ul. Vavilova 38, Moscow, 119991 Russia b Pirogov Russian National Research Medical University, ul. Ostrovityanova 1, Moscow, 117997 Russia c Bauman Moscow State Technical University, ul. Vtoraya Baumanskaya 5, Moscow, 105005 Russia d Institute of Applied Physics, Russian Academy of Sciences, ul. Ulyanova 46, Nizhny Novgorod, 603950 Russia e National Research Nuclear University Moscow Engineering Physics Institute, Kashirskoe sh. 31, Moscow, 115409 Russia f Moscow State University of Information Technologies, Radio Engineering, and Electronics, pr. Vernadskogo 78, Moscow, 119454 Russia e-mail: [email protected] Received August 6, 2014; in final form, January 26, 2015
Abstract—Low-frequency modulation of the gyrotron power at the L-2M stellarator was studied at different modes of plasma confinement. The plasma was heated at the second harmonic of the electron gyrofrequency. The effect of reflection of gyrotron radiation from the region of electron-cyclotron resonance plasma heating, as well as of backscattering of gyrotron radiation from fluctuations of the plasma density, on the modulation of the gyrotron power was investigated. DOI: 10.1134/S1063780X15080012
1. INTRODUCTION Modulation of the microwave power used for electron-cyclotron resonance heating (ECRH) of plasma in magnetic confinement systems can affect the heating efficiency by enhancing or suppressing unstable plasma fluctuations. Spontaneous modulation of the gyrotron power occurs as a result of the action of the radiation reflected (scattered) from plasma density fluctuations on the gyrotron operation [1]. The scattered radiation can be modulated in the amplitude or/and phase. The characteristics of backscattered radiation depend on the nature of instabilities occurring in the plasma confinement system; therefore, the problem arises of how the parameters of gyrotron radiation depend on the characteristics of backscattered radiation in different plasma confinement modes. In [2], it was shown that the spectrum of gyrotron power modulation in the standard L-2M magnetic configuration differs from that in the topologically unstable magnetic configuration (in which the rotational transform changes its sign inside the plasma column). In that paper, however, the characteristics of backscattered radiation were not studied. As was shown in [3], the spectrum and power of backscattered radiation
depend on the ECRH power. Therefore, it is of interest to study modulation of the gyrotron power in heating modes with a high ECRH power. The energy and spectrum of plasma fluctuations and, accordingly, the intensity of backscattered heating radi
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