Testing of a High-Power Generator of the Auxiliary Plasma Heating System of the KTM Tokamak with an Active Load

Alexandr Gulkin, Baurzhan Chektybayev, Anuar Kusainov, K. Zhenis, Vladimir Savkin, S. Kotov, D. B. Zarva, Saule Mukeneva, Yerzhan Kashikbayev, Dmitriy Olkhovik

3 more authors

baev Vasiliy, Aleksandr Gubin, Dmitriy Getman

Plasma, 2026

Full text Open access: Gold Metadata (CSL-JSON)
DOI 10.3390/plasma9040042
Data confidence 70 medium
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Abstract

At present, one of the key challenges in the development of controlled thermonuclear fusion (CTF) facilities is to ensure stable auxiliary plasma heating to the parameters required to sustain long-duration, high-power discharges. To achieve such operating regimes in tokamaks, reliable operation of ion-cyclotron resonance heating (ICRH) systems is required. These systems must be capable of efficiently transferring megawatt-level radio-frequency (RF) power to the plasma under substantially varying load conditions. Of particular importance is the commissioning of high-power RF generators, since tuning and impedance-matching errors can result in damage to expensive equipment and significantly increase the time required to prepare for experimental campaigns. Despite considerable experience in the application of ion-cyclotron resonance heating (ICRH) systems at tokamak facilities worldwide, the testing and commissioning of high-power triode-based generators using load equivalents remain relevant for each specific system. This is due, among other factors, to the individual characteristics of the antenna–feeder path, matching devices, and generator specifications. For the KTM tokamak, this task is of particular importance because commissioning of the ICRH system is a prerequisite for achieving the plasma parameters required to investigate the behaviour of promising candidate materials for the first wall and divertor under conditions as close as possible to those expected in future fusion reactors. In this work, an active load equivalent based on an aqueous saline solution was developed and used to experimentally test a high-frequency generator based on GU-98AM triodes operating in push–pull mode. The generator was tested at a reduced anode voltage of up to 5 kV, with stable RF generation at 13.1 MHz and RF power transfer of up to approximately 20 kW to the active load equivalent. These results demonstrate the applicability of the developed active load equivalent for preliminary tuning and testing of the RF generator and antenna–feeder system. The obtained results are limited to the reduced-voltage and reduced-power conditions investigated in this study and do not represent validation at the nominal anode voltage of 18 kV and rated RF power of 2 MW.