Abstract
Using laser-induced fluorescence, measurements of parallel ion velocities were made along the axis of a helicon-generated Ar plasma column whose radius was modified by spatially separated mechanical and magnetic apertures. Ion acceleration to supersonic speeds was observed 0.1-5 cm downstream of both aperture types, simultaneously generating two steady-state double layers (DLs) when both apertures were in place. The DL downstream of the mechanical aperture plate had a larger potential drop, Δ φDL =6-9 k Te, compared to the DL downstream of the magnetic aperture, Δ φDL ∼3 k Te. In the presheath region upstream of the mechanical aperture, the convective ion speed increased over a collisional distance; from stagnant at 4 cm from the aperture to the 1.4 times the sound speed at the aperture. The dependence of the free- and trapped-ion-velocity-distribution functions on the magnetic-field strength and mechanical-aperture electrical bias are also presented.
Original language | English (US) |
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Article number | 103509 |
Pages (from-to) | 1-8 |
Number of pages | 8 |
Journal | Physics of Plasmas |
Volume | 12 |
Issue number | 10 |
DOIs | |
State | Published - 2005 |
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics