Density limit in helicon discharges

Density jump in helicon discharges

Helicon discharges characteristically exhibit a sharp jump from low to high density as the radiofrequency (RF) power is raised. This is usually explained by the transition from an inductively coupled plasma (ICP) mode to a helicon mode when the dispersion relation for helicon wave propagation is satisfied at a critical power or magnetic field. Experiments have suggested a different mechanism fo...

Upper Limit to Landau Damping in Helicon Discharges

The uncommonly high rf absorption efficiency of helicon discharges has been thought to be caused by Landau damping of helicon waves and the concomitant acceleration of primary electrons. By constructing an energy analyzer that accounts for rf fluctuations in plasma potential, it is shown that Landau-accelerated electrons are too sparse to explain the ionization efficiency. Instead, rf absorptio...

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

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 ...

Low-field helicon discharges

Operation of helicon discharges at magnetic fields B0 below 100 G is of interest for plasma etching and deposition reactors if high ion flux can be maintained with reduced field requirements. The theory of coupled helicon and Trivelpiece–Gould modes is summarized for uniform B0. Initial results from two experiments are reported. The first has a single 5 cm diameter tube with B0 = 0–100 G inject...