Design and Operational Strategies for Mitigating Static After Cavity Interaction Based on the European ITER Gyrotron

Abstract Gyrotrons are essential sources for electron cyclotron resonance heating in magnetic confinement fusion devices. Achieving high overall efficiency and the nominal design power in these devices is a critical requirement. However, discrepancies between theoretical models and experimental results often arise because real systems exhibit additional effects that are not fully captured in idealized simulations. One such effect is the static after-cavity interaction (ACI) of the same transverse electric (TE) mode in the cavity uptaper and quasi-optical launcher, which can significantly reduce performance. A thorough understanding of ACI, supported by advanced simulation tools, is essential to identify effective mitigation strategies. Practical measures include fine adjustments of the magnetic field, operation at alternative working points, or modifications to the launcher geometry. Such approaches offer promising potential to enhance overall efficiency in gyrotrons for present and future fusion applications.