Summary of the Europhysics Topical Conference on Radiofrequency Heating and Current Drive of Fusion Devices

Abstract

In recent years, impressive progress has been made both on the physics understanding and on the power handling of the main RF systems: Ion Cyclotron Resonance Frequency (ICRF), Lower Hybrid Waves (LH), Electron Cyclotron Resonance Frequency (ECRF). In many large experiments, RF techniques are now being considered as a tool to improve plasma performances and to understand the physics of tokamaks or stellarators. For instance, H-modes have been achieved with all methods, with low levels of impurities, ICRF has allowed to heat and to produce plasmas at very high densities with high n tau T, as well as plasmas where most of the current is bootstrap driven and off-axis ICRF and ECRH have been used to understand energy radial transport. Large plasma currents have been driven by LH waves, up to 2 MA in conjunction with ICRF or Neutral beams. Fast Wave Ion current drive has been shown to have large efffects on MHD activity. Use of synergistic effects between LH and ICRF waves appear to be a possible route to increase current drive efficiency.More than 200 MJoules of ICRF and 100 MJoules of LH power have been launched recently on one minute long plasma discharges with plasma current up to 2 MA. The development of powerful ECRH sources at high frequency is steadily progressing. Steady state ignited plasmas require current drive efficiencies which are still exceeding present achievements, but a few approaches to the problem have been discussed. Heating to ignition with ICRF is very promising both on the physics and on the technical side since present power and energy handling capability are comparable to those needed for a reactor. In addition to reaching ignition in fusion reactors, other roles for RF waves, such as burn control and profile control, have been extensively discussed.