Time and space resolved measurements of optical emission and wave magnetic field components have shown the relation between energy loss from the Helicon wave and energy gain by plasma electrons. This non-linear wave-particle trapping is related to Landau Damping and provides the best explanation yet found for the surprising efficiency of the Helicon source. The results agree well with a 3D theoretical model.
Coupling between the antenna near field (a forced oscillation which couples inductively to the plasma under the antenna) and the travelling Helicon wave has been studied both analytically (Prof. R. Dewar) and computationally using a combined Particle-in-Cell/fluid code.
Helicon plasmas are proving a rich field for the study of transport phenomena. Along the magnetic field linking the source to the diffusion chamber, an electric field can be created which accelerates the ions toward the substrate. For a strongly expanding plasma, this field can degenerate into a double layer which separates the source plasma and the diffusion plasma. An exactly analogous phenomena occurs in the Auroral regions and is responsible for accelerating the electrons which cause the Aurora. The 2D hybrid plasma code and PIC codes running on the Connection Machine (multiple and parallel processors) are used to analyse these phenomena.
The transition from capacitive to inductive coupling in the Helicon source presents some fascinating problems in cross field diffusion -- problems also encountered in toroidal geometry. Although only a few tens of gauss are applied to the plasma, in the inductive (high density, H mode) region, the cross field diffusion of ions decreases to below thermal velocity. Although measurements show the difference in the diffusion and correlate well with the differences in plasma density, the reason for the jump from one mode to the other is not known (neither is it known for toroidal systems).
Go Straight to the Source....the Helicon Source
The inventors of the Helicon Plasma Source, the SP3 group at the ANU, can now supply these versatile rf plasma source to your laboratory. For further information ....
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