RFEA Measurements of High-Energy Electrons in a Helicon Plasma Device with Expanding Magnetic Field

Gulbrandsen, Njål; Fredriksen, Åshild

doi:10.3389/fphy.2017.00002

Cited by 40 publications

(42 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Other groups have also reported hints of energetic electrons in their expanding helicon source plasmas. 35,44,45 Prior work in our own laboratory found a strong correlation between enhanced upstream density and the appearance of the downstream ion beam. For rf coupling levels that did not result in formation of an ion beam, the upstream plasma density was lower than when a beam formed.…”

Section: Discussionmentioning

confidence: 92%

Spatial structure of ion beams in an expanding plasma

et al. 2017

View full text Add to dashboard Cite

We report spatially resolved perpendicular and parallel, to the magnetic field, ion velocity distribution function (IVDF) measurements in an expanding argon helicon plasma. The parallel IVDFs, obtained through laser induced fluorescence (LIF), show an ion beam with v ≈ 8000 m/s flowing downstream and confined to the center of the discharge. The ion beam is measurable for tens of centimeters along the expansion axis before the LIF signal fades, likely a result of metastable quenching of the beam ions. The parallel ion beam velocity slows in agreement with expectations for the measured parallel electric field. The perpendicular IVDFs show an ion population with a radially outward flow that increases with distance from the plasma axis. Structures aligned to the expanding magnetic field appear in the DC electric field, the electron temperature, and the plasma density in the plasma plume. These measurements demonstrate that at least two-dimensional and perhaps fully three-dimensional models are needed to accurately describe the spontaneous acceleration of ion beams in expanding plasmas.

show abstract

Section: Discussionmentioning

confidence: 92%

Spatial structure of ion beams in an expanding plasma

et al. 2017

View full text Add to dashboard Cite

show abstract

“…As the downstream neutral pressure increases, the electric field at z ¼ 164 cm undergoes significant changes in amplitude, particularly along the edges of the plasma where energetic electrons are observed to stream out from the source into the expansion chamber. 17,25 The energetic electrons create an annulus of increased plasma density through enhanced ionization upstream and downstream of the source-expansion chamber junction. The radius of the annulus maps along the divergent magnetic field to a radius of one electron skin depth from the rf antenna in the plasma source.…”

Section: Resultsmentioning

confidence: 99%

Pressure dependence of an ion beam accelerating structure in an expanding helicon plasma

et al. 2018

View full text Add to dashboard Cite

We present measurements of the parallel ion velocity distribution function and electric field in an expanding helicon source plasma plume as a function of downstream gas pressure and radial and axial positions. The ion beam that appears spontaneously in the plume persists for all downstream pressures investigated, with the largest parallel ion beam velocities obtained for the lowest downstream pressures. However, the change in ion beam velocity exceeds what would be expected simply for a change in the collisionality of the system. Electric field measurements confirm that it is the magnitude of the potential structure responsible for accelerating the ion beam that changes with downstream pressure. Interestingly, the ion density radial profile is hollow close to the end of the plasma source for all pressures, but it is hollow at downstream distances far from the source only at the highest downstream neutral pressures.

show abstract

“…The excitation of the helicon wave often produces a high density plasma downstream of the source due to the wave propagating in the plasma column 32 . Several experiments in the expanding magnetic fields have shown that the high density conics are formed in the magnetic nozzles [33][34][35][36] . Two-dimensional measurement of an electron energy distribution has indicated that the high temperature electrons heated by the rf antenna field are transported along the expanding magnetic field 37 .…”

Section: Magnetic Nozzle Radiofrequency Plasma Thruster Approaching Twenty Percent Thruster Efficiency Kazunori Takahashimentioning

confidence: 99%

Magnetic nozzle radiofrequency plasma thruster approaching twenty percent thruster efficiency

Takahashi

2021

Sci Rep

View full text Add to dashboard Cite

Development of a magnetic nozzle radiofrequency (rf) plasma thruster has been one of challenging topics in space electric propulsion technologies. The thruster typically consists of an rf plasma source and a magnetic nozzle, where the plasma produced inside the source is transported along the magnetic field and expands in the magnetic nozzle. An imparted thrust is significantly affected by the rf power coupling for the plasma production, the plasma transport, the plasma loss to the wall, and the plasma acceleration process in the magnetic nozzle. The rf power transfer efficiency and the imparted thrust are assessed for two types of rf antennas exciting azimuthal mode number of $$m=+1$$ m = + 1 and $$m=0$$ m = 0 , where propellant argon gas is introduced from the upstream of the thruster source tube. The rf power transfer efficiency and the density measured at the radial center for the $$m=+1$$ m = + 1 mode antenna are higher than those for the $$m=0$$ m = 0 mode antenna, while a larger thrust is obtained for the $$m=0$$ m = 0 mode antenna. Two-dimensional plume characterization suggests that the lowered performance for the $$m=+1$$ m = + 1 mode case is due to the plasma production at the radial center, where contribution on a thrust exerted to the magnetic nozzle is weak due to the absence of the radial magnetic field. Subsequently, the configuration is modified so as to introduce the propellant gas near the thruster exit for the $$m=0$$ m = 0 mode configuration and the thruster efficiency approaching twenty percent is successfully obtained, being highest to date in the kW-class magnetic nozzle rf plasma thrusters.

show abstract

RFEA Measurements of High-Energy Electrons in a Helicon Plasma Device with Expanding Magnetic Field

Cited by 40 publications

References 39 publications

Spatial structure of ion beams in an expanding plasma

Spatial structure of ion beams in an expanding plasma

Pressure dependence of an ion beam accelerating structure in an expanding helicon plasma

Magnetic nozzle radiofrequency plasma thruster approaching twenty percent thruster efficiency

Contact Info

Product

Resources

About