Suprathermal electron physics in the TCV tokamak

Suprathermal electron physics in the TCV tokamak (Stefano Coda)

Highly energetic (“suprathermal”) electrons can be generated by various mechanisms, including externally launched electromagnetic waves and internal magnetohydrodynamic (MHD) instabilities. Invariably, they hold the key to understanding the phenomena that generate them. In the case of electron cyclotron resonance heating (ECRH), a powerful auxiliary heating technique that is planned for instability control in future reactors and is the centerpiece of the TCV tokamak, the suprathermal electron population mediates the physics of  heating and current drive. In the case of MHD, strong electric fields associated
with magnetic islands are responsible for accelerating electrons to high energies, and diagnosing these electrons is necessary to understand the dynamics of magnetic reconnection and island formation. Additionally, very high-energy runaway electrons are a strong concern for reactor integrity in the event of disruptions and their understanding is still uncomfortably rudimentary. TCV has been freshly equipped with a state-of-the-art, 4-camera hard X-ray (HXR) tomographic spectrometer, a powerful and unequalled diagnostic for the study of fast electrons. This is complemented by high-field-side and vertical ECE systems, tangential HXR detectors, a runaway detector, and a soft X-ray spectrometer. Modelling support is provided by two suites of Fokker-Planck quasilinear codes complemented by synthetic HXR diagnostics. There is huge potential for highly innovative thesis work breaking new ground in the physics of suprathermal electrons and associated phenomena, ranging from ECRH to MHD to runaway generation. A thesis can focus more on the diagnostic side, on the modelling side, or anywhere in between depending on individual aptitude.

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