Theoretical And Experimental Research On Helicon Plasma Thruster

Helicon plasma source has been shown to produce high-density uniform plasmasefficiently. Several years ago, the so-called phenomenon of current-free double layer inhelicon plasma sources was reported, and the compact helicon plasma thruster (HPT)became a hot concept in electric propulsion area. Nevertheless, the accelerationmechanism of plasma in a helicon plasma thruster is not yet verified completely, and thefurther development is thus hampered. In this paper, preliminary analysis on thrustergeneration mechanism, as well as the design and test of a helicon plasma thrustertest-bed (HPTT) was introduced.The propulsion contribution from neutral gas thermodynamic expansion and ionsejection driven by electromagnetic field are explored based on simplified models,respectively. The analysis results showed that the thrust caused by the ejection of theneutral gas is0.19mN with the propellant gas volume flow rate of20sccm and the backpressure of510-3Pa, whereas the thrust due to ions ejection is estimated to be about5.05mN under the same gas feeding condition, supposing that the electron temperatureequals to4eV.A helicon plasma thruster test-bed (HPTT) was constructed based on the laboratoryfacilities. The HPTT consists of a helicon antenna and six subsystems, including RFdelivery, working medium feeding, magnetic field generation, support structure,temperature and magnetic field measurement, and plasma diagnosis system. The designand integration of each subsystem in HPTT were given in detail. As a preliminary testresult, a axial, near-uniform magnetic field of variable magnetic flux density with themaximum value of0.2T is implemented in the bulk of L100×Φ50mm. The ionizationof Ar and N2were demonstrated with the RF power up to400W and the gas volumeflow rate is between15and30sccm.The preliminary measurements of plasma temperature were conducted by themethod of plasma optical emission spectrum (OES). Under the conditions that themagnetic flux density of805G, the RF power of200W and the volume flow rate of25sccm, the electron temperature is deduced to be about4eV. Several factors that havedirect effect on the electron temperature were explored with experiments, includingmagnetic flux density, RF power, and gas volume flow rate. It was concluded that underthe range of experiment condition, the electron temperature arises with the increase ofmagnetic flux density, arises in the beginning and then declines with the increase of RFpower, declines with the increase of working medium flow rate.