Characterization of runaway electron generation during ohmic plasma startup
2024 Research Campaign, ITER Integrated Scenarios
Purpose of Experiment
Plasma initiation in ITER require specific conditions including a low prefill pressure. As a result, the plasma density will be low during the breakdown, which has been shown to increase the generation of runaway electrons (REs). If a large current is carried by RE, it could cause damage to plasma facing components and should be prevented. This experiment aims to document and investigate the dependence of runaway electron characteristics on plasma parameters during plasma start-up. Data collected from this experiment will help validate existing simulation codes and improve our understanding of RE energy dynamic during tokamak start-up.
Experimental Approach
The experiment involves three separate scans and utilizes the unique gamma ray imager {GRI) diagnostics. The GRI diagnostics is capable of measuring the electron distribution function of REs during RE growth and dissipation. Our goal is to vary the RE characteristics by adjusting plasma parameters such as density, temperature and current. The shot plan begins with conditions that do not produce identifiable REs, and then makes the largest change in prefill pressure to generate REs that are visible to different diagnostics. In the subsequent cases, we will adjust prefill pressure, current ramp time and include auxiliary heating to empirically document the changes in RE characteristics.
See more details, including project leads, at U.S. Department of Energy, Office of Scientific and Technical Information (OSTI).