Understanding Temporal Plasma Density Depletion in LVPD-U Using Plasma Flow Measurement

Cross filed transport across magnetic fields is a complex process relevant to magnetosphere, fusion machines, Hall effect thrusters, magnetrons, and other plasma based technologies. In the Large Volume Plasma Device – Upgrade (LVPD-U), it is observed that plasma diffusion from the source to the target plasma region through the Electron Energy Filter (EEF) region exhibits time dependency influenced by the transverse magnetic field of EEF [1]. The cross field transport depends on various factors such as source plasma density, EEF field strength, system geometry, plasma collisionality, and can be understood through different diffusion processes, including classical, anomalous, and Bohm diffusion.

 

This study focuses on analysis of Mach probe [2] data to investigate the space and time-varying density function of a diffused plasma across a high magnetic field. A noticeable observation, probably not yet reported is made, exhibiting non-linear dependency of the density decay rate with the strength of transverse magnetic field. Exploration of this phenomenon further for different EEF magnetic field strengths, density function exhibit an inverse relationship with time. These observations suggest a need for making use of advance models that incorporate elements of anomalous and Bohm diffusion in order to accurately describe plasma transport in cross field diffused plasma.  We believe that outcome from such initiatives will help in enhancing the existing knowledge base on cross-field transport in laboratory plasma, fusion plasma and help in developing better efficiency in plasma-based technologies.