Investigation of Ion Movement Patterns and Properties Within a Magnetic X-point System

The formation of a magnetic null point in an X-point system presents an interesting case for plasma dynamics. Understanding the effect of this uncommon magnetic field configuration, especially on ions, may be influential in progressing plasma research and applications. In this study, a non-invasive optical diagnostic system, Laser-Induced Fluorescence (LIF) is implemented in a multi-dipole chamber called MAXIMUS [1] which is able to simulate a magnetic X-point much like a tokamak divertor. The diagnostic is specially developed focusing on enabling measurements at various locations of the X-point configuration, exploring various magnetic flux line shapes. The properties of ions and how they change due to the magnetic field are inferred and discussed through examining the ion velocity distribution function (IVDF). Especially, detailed analysis at how the IVDF may deviate from the Maxwellian form is done, since it may indicate significant and more interesting phenomena, such as charge exchanges or instability-enhanced collisions.

[1] Lim, Yegeon, et al. "New low temperature multidipole plasma device with a magnetic X-point and its properties." Plasma Sources Science and Technology 29.11 (2020): 115012.