Effect of the radial magnetic field strength on the argon plasma characteristics of an inductive radiofrequency plasma thruster with a time-varying magnetic field

This study investigates an inductively-coupled radiofrequency plasma thruster subjected to a time-varying diverging magnetic field in conjunction with a static radial magnetic field to enhance plasma acceleration. A variable radial magnetic field is generated using an electromagnet to assess its effects on argon plasma characteristics. Static magnetic fields are applied separately and jointly with time-varying magnetic fields to analyze their decoupled and synergistic effects, respectively. Non-acceleration mode results without time-varying magnetic fields show that as the radial magnetic field strength increases such that the electron gyroradius decreases, the electron temperature and plasma potential increases monotonically resulting in steep axial gradients at high magnetic field strengths. As a result, perpendicular electric fields experience monotonic enhancement coincident with a non-monotonic 50% plasma density drop. Additionally, the region where the plasma density is maximal shifts downstream toward the thruster exit as the magnetic field strength increases. At relatively higher magnetic fields, the plasma density drop saturates but the plasma potential and electron temperature continue to rise. Similar trends successfully recur in acceleration mode measurements when both magnetic fields are jointly applied. The key difference between decoupled and synergistic effects seems to be plasma parameter enhancement enabled by the additional electrical power in acceleration mode.