Control system development and testing for the electron beam current of ITER European gyrotrons

The Electron Cyclotron Heating system represents one of the plasma heating mechanisms for tokamaks. It is based on the employment of gyrotrons, such as vacuum tubes that exploit the cyclotron resonance of electrons to generate a coherent electromagnetic beam that is sent to the plasma. In the current ITER baseline, the Electron Cyclotron Heating is of crucial importance since gyrotrons are expected to provide on-demand megawatt power at any time during operation. Gyrotrons are complex machines and their reliability during long pulse operations depends on the closeness of the initial conditions to the nominal operating point. Currently, very short pulses are performed to check the state of the machine before performing a long one. With the requirements of ITER baseline, a more robust control is needed, capable of controlling the radio-frequency emission and preparing the tube in the fastest way possible during the transient times between pulses. In this work, a controller based on a thermal model of the gyrotron electron gun is developed using MARTe2, a framework for real-time control applications. First, a model-based feed-forward waveform is developed and tested on a real machine to validate the feasibility of the model-based approach. Afterward, a complete simulation of the controller is carried out to test the developed control logic and assess the effect of the inevitable differences between the dynamics of the model and the actual device. The purpose is to provide a flexible tool to be integrated in the gyrotron control system to improve the reliability of the Electron Cyclotron Heating system for ITER operations.