Exploration of Ion Heat Pulse Propagation Experiments in W7-X

Understanding and control of turbulent transport in high temperature plasmas is one of the most important topics of fusion energy science as turbulence degrades the plasma performance above critical gradient lengths. To study the corresponding stiffness of heat transport, i.e. to analyze how strong heat fluxes increase with the normalized temperature gradient length, power modulation studies are a commonly applied technique for the electron channel [1] but similar studies considering the ion channel have hardly been performed. Here, we present the design and concept of a new high speed ion temperature diagnostic for W7-X, as well as numerical tools developed to perform ion heat pulse propagation studies using neutral beam injection (NBI) modulation. Moreover, first results obtained during the previous experimental campaign are discussed which lack fast enough ion temperature measurements but show a clear impact of NBI modulation on the electron temperature profile.

[1] G.M. Weir, Nucl. Fusion 61 (2021) 056001