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.

In the Kazakhstan Material Testing Tokamak (KTM), additional plasma heating will be achieved by injecting power in the ion cyclotron resonance frequency range using four identical generators, each delivering 2 MW of output power. Prior to transitioning the KTM into regular operation, it is necessary to tune these generators using a load equivalent that simulates plasma-like operating conditions. This article presents the electrodynamic design and analysis of a load equivalent capable of absorbing up to 2 MW of high-frequency power. The geometry and key parameters of the load equivalent for the additional high-frequency (HF) plasma heating system of the KTM tokamak are defined. The calculations are based on the assumption that the optimal solution is to construct the load equivalent as a resonator containing a saline aqueous solution absorber housed in a tank with a dielectric window. A dielectric material with high permittivity is proposed for use in the resonator structure. The results demonstrate that the developed load equivalent enables effective testing and tuning of the high-power generators, thus ensuring the readiness of the additional power injection system for scheduled activation on the KTM tokamak. Two plasma load equivalent (PLE) configurations were investigated for different bench-testing purposes. The large PLE was optimized for high RF power absorption in the standing-wave regime, whereas the small PLE was designed to provide a low-impedance loading condition for antenna-matching tests in preparation for plasma operation.