03pB02
磁気ノズル中径方向拡散の抑制によるヘリコンスラスターの性能向上

Performance improvement of a helicon plasma thruster
by inhibiting a cross-ﬁeld diﬀusion in a magnetic nozzle
高橋和貴, CHARLES Christine1 , BOSWELL Rod1 , 安藤晃
Kazunori TAKAHASHI, Christine CHARLES1 , Rod BOSWELL1 , Akira ANDO
東北大工, オーストラリア国立大 SP31
Tohoku Univ., The Australian National Univ.1Thrust (mN)Over the past few decades, various electric propulsion devices such as ion gridded thrusters and hallthrusters have been developed ans successfully tested in space. The new concept of electrodeless plasma
thruster called “HELICON THRUSTER” is recently investigated theoretically [1,2] and experimentally[3,4]. The helicon thruster has a simple structure consisting of an insulator source cavity wound by a rfantenna and a magnetic nozzle, which can be provided by solenoids and/or permanent magnets. Someof the theories and experiments have suggested that the axial plasma momentum can be increased by amagnetic nozzle due to a presence of a spontaneous azimuthal plasma current (mainly electron diamagnetic
drift current) and the radial magnetic ﬁeld. It would be important to understand the plasma ﬂow dynamics
in the magnetic nozzle, which appears to be more complex than people thought because of the presenceof the magnetic ﬁeld, heating source, physical boundaries, non-Maxwellian electron energy distribution [5],and so on.
Here laboratory experiment of a helicon plasma
15thruster is established to control only the plasma crossTtotalﬁeld diﬀusion in a rapidly-divergent magnetic nozzle,
while maintaining a constant plasma injection into the10magnetic nozzle. Measurement of the plasma denTB
sity shows that the unchanged plasma density within
the source cavity while increasing the density in the5magnetic nozzle when increasing the solenoid current
Ts(not shown here). The radial measurements suggest
the cross ﬁeld diﬀusion can be inhibited by the ﬁeld
0Tw
strength and yield the higher plasma density in thenozzle. The thrust is equal in magnitude and opposite in direction to the force imparted to the thruster−5structure. The force components imparted to axial (Ts )051015and radial (Tw ) source boundaries and to the magnetic
solenoid current (A)Fig1. Directly measured thrust components Tsnozzle (TB ) are independently measured with changing(crosses), Tw (open triangles), TB (open squares),the cross-ﬁeld diﬀusion and the resultant plasma ﬂow
andTtotal (ﬁlled circles) as a function of the solenoid
in the magnetic nozzle. The results show a constantcurrent, together with the theoretical limit of TB
force to the axial boundary, a negligible force to the(solid line) for the presently measured electron presradial boundary, and an increasing force to the magsure near the source exit.
netic nozzle, with an increasing the ﬁeld strength ofthe magnetic nozzle. It is found that the measured
thrust component TB is approaching the theoretical limit of the electron diamagnetic-induced thrust derived from an ideal magnetic nozzle approximation. The total thrust Ttotal corresponding to Ts + Tw + TB
also increases simultaneously with increasing the TB components.
[1] A. Fruchtman, Phys. Rev. Lett. 96, 065002 (2006).
[2] E. Ahedo and M. Merino, Phys. Plasmas 17, 073501 (2010).
[3] K. Takahashi, T. Laﬂeur, C. Charels, P. Alexander, and R.W. Boswell, Phys. Rev. Lett. 107 235001 (2011).
[4] K. Takahashi, C. Charles, and R.W. Boswell, Phys. Rev. Lett. 110 195003 (2013).
[5] K. Takahashi, C. Charles, R.W. Boswell, and T. Fujiwara, Phys. Rev. Lett. 107 035002 (2011).