ICRH system for the Ignitor machine

The ICRH system adopted for the Ignitor machine is characterized by a maximum power delivered to the plasma of 18 MW and a wide range of operating frequencies (100<ν<210 MHz). The main functions of the system are to control the time evolution of the plasma temperature and the toroidal current density profiles, to keep the region where g<1 small and to suppress the possible onset of sawtooth oscillations by fast particle stabilization in relatively low plasma density discharges. The ICRH system can also be used to accelerate the attainment of ignition, to extend the conditions under which ignition is possible, to explore the conditions under which the second stability region of finite β plasmas can be achieved, to produce significant levels of power from D-³He fusion reactions, to reduce the Volt-sec requirement and to perform current drive experiments in low density discharges (n_e<2×10²⁰ m^-3 ). The wide range of frequencies has been adopted in order to operate in different regimes (ω=ω_CD, ω(C ³)_He, 2ω_CT, ω_CH at maximum toroidal magnetic field). This additional source of heating allows Ignitor to produce a significant level of α power in low plasma current and low toroidal magnetic field discharges, while operating at lower mechanical and thermal stresses and sustaining the discharges for a longer period of time. The ICRH system is composed of 6 antennae, completely inserted in first wall recesses, that are driven by amplifiers through the equatorial ports of the machine. Each antenna module composed of straps grouped in poloidal pairs, is able to couple up to 3 MW of heating power to the plasma