Evaluation of Plasma Flow and Acceleration Effect Using Rotating Magnetic Field Current Driving Method in Magnetic Nozzle

Rotating Magnetic Field (RMF) current driving is utilized to form Field Reversed Configuration (FRC) in the field of nuclear fusion research [1] and accelerate plasma in electrodeless Radio Frequency (RF) plasma propulsion [2]. The RMF plasma acceleration is proposed for performance improvement of the RF plasma thruster by increasing an electromagnetic force under a magnetic nozzle [3]. The RMF method drives an azimuthal electron current owing to the non-linear Hall-term effect, and the additional force is generated in the presence of the external divergent magnetic field.

To optimize the plasma acceleration effect in our proposed RMF thruster concept, we measured and investigated the spatial profiles of plasma parameters, including Ion Velocity Distribution Function (IVDF) using laser-induced fluorescence velocimetry [4]. An increase in the axial component of the IVDF was found showing the additional plasma acceleration effect via electron current driving under the magnetic nozzle. We also compared two-dimensional spatial profiles of the ion flow vectors varying the RMF rotational frequency, which affects the RMF penetration into plasma, to clarify the dependence of the ion flow on the frequency. It was suggested that multiple plasma acceleration is yielded by the RMF method, not only for the full penetration of the RMF but also even when the RMF penetration is not fully accomplished [5].