Radial characterization of an ion beam in a deflected magnetic nozzle

Abstract

The radial characterization of an ion beam generated in a magnetically steered radio-frequency (RF) plasma source is presented. In the symmetrical magnetic nozzle (MN) configuration, radial profiles of the ion saturation current obtained with a planar Langmuir probe show a double-peaked profile. The same behaviour is confirmed by the radial measurements of the total ion current and the ion energy distribution functions (IEDFs) obtained with a retarding field energy analyzer. The IEDFs also show the presence of an ion beam centred at $$r = -2$$ r = - 2 cm. On the contrary, radial measurements taken with a magnetic nozzle deflected on the $$r - z$$ r - z plane exhibit a single-peaked profile with both the local ion population and the ion beam centred at $$r = -5$$ r = - 5 cm, in the direction of the MN orientation. It is shown that the ion beam location is changed as a result of a deflected magnetic nozzle, and that it follows the direction of increasing radial magnetic field.

Data Processing Techniques for Ion and Electron Energy Distribution Functions

“…4, the ionenergy distribution functions show a double-peak feature indicating the presence of a bi-population of ions: the first peak represents the background ion population (at zero energy) which location can be considered the local plasma potential V p , while the second peak corresponds to the accelerated ion beam population with potential V B end energy ε B = e(V B − V p ). Comparing measurements taken with a source-facing and a radial-facing RFEA shows that the IEDF does not present a peak separation effect due to RF modulation, but it effectively detects the presence of a directional ion beam 31 . It is also noted that the ion-neutral mean free path for the operating pressure of 0.5 mTorr is shorter than the distance between the source exit and the probe position i.e., λ i ∼10 cm and z p = 19 cm.…”

Plasma acceleration in a magnetic arch

“…Nevertheless, when ion magnetization is weak (B 0 ⩽ O( 1)), the last term in the ion momentum equations (the ion magnetic force) is typically small. Then, if u yi ≪ 1 initially, it remains so everywhere else, and the electron magnetic force dominates in the right hand side of equations ( 16) and (17).…”

“…the helicon plasma thruster [9][10][11][12] and the electron-cyclotron plasma thruster [13][14][15]. Additionally, nonaxisymmetric MNs have been proposed for contactless thrust vector control [16,17].…”

Effects of magnetic nozzle strength and orientation on radio-frequency plasma expansion

“…The secondary grid is biased at −18 V to repel secondary electrons caused by ion bombardment on the collector plate. The design of this probe is based on energy analysers extensively used in similar devices [6,7,19,23,39,40]. The probe orifice is placed perpendicularly to the plasma source exit so that the presence of a directional ion beam could be detected.…”

“…Numerous experiments and simulations have reported the formation of a hollow density structure, also called highdensity conics, in the diffusion region of an RF plasma expanding in a symmetric magnetic nozzle [13][14][15][16][17][18][19][20][21][22][23][24]. A common feature in the literature is the concomitance of the conics with the most radial streamlines leaving the source.…”