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Measurements of fast electron bremsstrahlung (FEB) using hard X‐ray (HXR) cameras provide a unique diagnostic for the fast electron dynamics, with resolution in space, time and energy. A synthetic HXR diagnostic is developed to calculate the distribution function and FEB emission, such that experimental results can be directly compared with simulations. Using this comparison, the role of fast electron radial transport in radio‐frequency current drive is investigated. For two cases studied in this paper, the HXR emission is consistent with negligible radial transport, although in one case this is in disagreement with the measured driven current.

Electron cyclotron resonance heating (ECRH) and current drive (ECCD), disruptive instability events and sawtooth activity have been demonstrated to produce suprathermal electrons in fusion devices. The importance of these phenomena for fusion reactors renders suprathermal electron generation and dynamics a key topic in the physics of burning plasmas. Here some significant results from the TCV tokamak are briefly reviewed and a preliminary design of a novel tomographic hard X-ray spectrometer proposed for TCV is discussed. The design is aided by simulations of tomographic reconstruction.

Methods of modifying sawtooth oscillations using waves in the ion cyclotron range of frequencies (ICRF) in the JET tokamak are presented. Examples of sawtooth stabilization by ICRF-accelerated high ...