Parametric Decay Instability Physics in Helicon Injection Without Neutral Beams
2024 Research Campaign, Heating and Current Drive
Purpose of Experiment
This experiment is to increase our quantitative understanding of a phenomenon known as parametric decay instabilities (PDI). PDI occurs when electromagnetic waves at high power levels propagate in plasmas, and as such occurs in laser fusion experiments as well as in experiments in tokamaks in which high-power radiofrequency waves are launched into the plasma for the purpose of heating and driving non-inductive current in the core of the plasma. In PDI, some fraction of the electromagnetic wave power applied to the plasma excites waves at frequencies other than the applied frequency, and as such can constitute a loss mechanism for the intended heating and current drive. In this particular experiment, the intention is to study plasmas in which only rf heating is applied, and none of the neutral beams are used. This is done partly because the neutral beams themselves can create instabilities of a similar nature (where they are called Ion Cyclotron Emission or ICE), so in plasmas with both rf and neutral beams, the situation can get confusing.