The performance of a permanent magnet helicon plasma thruster (PM-HPT) is improved by modifying the magnetic field configuration and increasing the magnetic field strength for operating source conditions of 13.56 MHz radiofrequency power up to 2 kW and 24 sccm of argon (pressure of ∼0.8 mTorr). A convergent-divergent magnetic nozzle giving a maximum field strength of ∼300 G is provided by arrays of permanent magnets, giving a higher plasma density downstream of the thruster exit (hence a larger Lorentz force within the magnetic nozzle) compared with that measured in the previous PM-HPT experiments (Takahashi et al 2011 Appl.Phys. Lett. 98 141503; Takahashi et al 2011 Phys. Rev. Lett. 107 235001). The directly measured thrust and specific impulse are about 15 mN and 2000 s, respectively, for a thrust efficiency of 7.5%.
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