REVIEW ARTICLES Physics of helicon discharges*

Helicon discharges and sources: a review∗

Helicon waves are waves in low-temperature, partially ionized plasmas in a dc magnetic field (B-field). The study of helicons involves both ion–neutral collisions and Larmor orbits, even when the B-field is uniform. Helicon discharges are ionized by helicon waves generated by a radiofrequency (RF) antenna. Interest in helicon discharges arose because of the high plasma densities they generate c...

The low-field density peak in helicon discharges

Although the density n in helicon discharges increases monotonically with magnetic field B for B larger than a few hundred gauss, as expected from theory, a pronounced density peak is often observed at B;50 G or below. A peak in antenna loading is indeed found in computations using a fluid code as long as reflections from an endplate are taken into account. Various tests show that this peak is ...

Comment on "Upper limit to Landau damping in helicon discharges".

Spatially limited ion acoustic wave activity in low-pressure helicon discharges

Ion acoustic wave phenomena are studied and compared in two low-pressure argon discharges created by helicon sources. The wave amplitudes are spatially localized near the edge of a plasma column as the amplitudes of the “mirror waves” that are separated from the helicon source frequency by the ion wave frequency. Dependencies of the ion wave on radial position, pressure, input power, and magnet...

Equilibrium theory of cylindrical discharges with special application to helicons

Radiofrequency discharges used in industry often have centrally peaked plasma density profiles n(r) although ionization is localized at the edge, even in the presence of a dc magnetic field. This can be explained with a simple cylindrical model in one dimension as long as the short-circuit effect at the endplates causes a Maxwellian electron distribution. Surprisingly, a universal profile can b...