Spatially Excited Magnetic Field Profiles in Rotating Magnetic Field Plasma Acceleration Scheme*

To fulfill a long lifetime, manned space propulsion system, Helicon Plasma Thruster (HPT) [1,2] has been proposed, due to a high-dense plasma generation and no wear of electrodes. As an additional plasma acceleration scheme in the HPT, Rotating Magnetic Field (RMF) method [2,3] is being studied. The RMF is induced by using two-phased, opposing coils, with current phase differences between the two sets of coils, and an azimuthal current can be induced by the non-linear effects. Then, the axial Lorentz force is expected to be generated in the presence of an external divergent magnetic field. Here, spatial rf RMF measurements were conducted to examine the acceleration effect by the use of a three-axis B-dot probe, as well as other effects. The axial forward force can be estimated since the DC azimuthal current induced by the RMF is comparable to AC one with twice of the RMF frequency. [1] S. Shinohara, Phys. Plasmas 16 (2009) 057104. [2] S. Shinohara et al., IEEE Trans. on Plasma Sci. 42 (2014) 1245. [3] T. Furukawa, et al., Phys. Plasmas 24 (2017) 043505.