Study of arcing in transmission lines for RF plasma heating and scaling of the energy confinement time in tokamaks

ICRF power coupling to plasmas in fusion devices is limited by a number of breakdown phenomena. This project focuses on the experimental characterization of arc triggering phenomena on the IShTAR test stand (IPP Garching). For that purpose, the IShTAR device is being modified in order to install a resonating circuit, which will allow studies of RF breakdown under tokamak conditions and arcing in coaxial lines. The generation of the RF high voltage will be realized via a 1 kW amplifier and a resonating circuit. A data acquisition system is designed for the electrical measurements on the resonator (forward and reflected power, voltage and current), with high temporal resolution. A fast camera and a photomultiplier triggering system are installed for imaging of the arcs.

The second part of the project is related to the estimation of the global energy confinement scaling in tokamaks. The H-mode energy confinement scaling is one of the most important scaling laws in fusion research and a critical tool for design and operation of new fusion devices, while providing boundary conditions for modeling activities. Advanced regression analysis methods using Bayesian inference and information geometry will be applied to revise the confinement scaling using the most recent update of the international global H-mode confinement database. More flexible models than the classic power law will also be investigated.