A radiofrequency heating method that uses antennas inside the vacuum vessel to launch waves at the ion cyclotron frequency, directly heating ions in the plasma core.
ReviewedLast reviewed: 9 Aug 2026·Category: Glossary
Principle
ICRH (also called ICRF — ion cyclotron range of frequencies) launches electromagnetic waves at frequencies matching the ion cyclotron frequency or its harmonics, typically 20–120 MHz. Antennas mounted on the vacuum vessel wall couple power into fast magnetosonic waves that propagate to the plasma core, where they are absorbed by ions at the cyclotron resonance.[1]
Minority heating: The most common ICRH scheme heats a minority ion species (e.g., hydrogen in a deuterium plasma) at its cyclotron resonance. The minority ions absorb the wave energy efficiently, then transfer it to the bulk plasma through collisions. JET used up to 12 MW of ICRH; ITER plans 20 MW at 40–55 MHz.
Advantages and Challenges
ICRH directly heats ions (unlike ECRH, which heats electrons), making it particularly effective for scenarios requiring high ion temperatures. It can also accelerate specific ion species for nuclear reaction studies.[2]
Challenges include: antenna–plasma coupling in the edge region, impurity generation from antenna–wall interactions, and parasitic absorption at the plasma edge. Alcator C-Mod used ICRH as its sole auxiliary heating method (up to 5 MW) and achieved world-record plasma pressure.[3]
Sources
Wesson, J. Tokamaks. 4th ed., Oxford University Press, 2011, Chapter 5.
Wilson, J.R. and Bonoli, P.T. "Progress on ion cyclotron range of frequencies heating physics and technology in support of the ITER project." Physics of Plasmas, 22(2), 021801, 2015.
Greenwald, M. et al. "20 years of research on the Alcator C-Mod tokamak." Physics of Plasmas, 21(11), 110501, 2014.