Helicon discharges and sources: a review

Abstract

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 compared with other RF sources at comparable powers. The semiconductor industry has not taken advantage of this, even since the possible use of permanent magnets for the B-field has been demonstrated. Nonetheless, a large literature on helicons has evolved because of the numerous problems these discharges posed and the interesting physics found in their solutions.

Whistler waves with angular momentum in space and laboratory plasmas and their counterparts in free space

“…Whistler modes were also excited in discharge plasmas produced in the laboratory [9]. The waves in bounded plasma columns were termed 'helicons' [10] and a new specialty of low temperature plasma applications evolved [11]. Many laboratory experiments were dedicated to understand the properties of whistler modes in space plasmas [12,13].…”

“…It turned out that helicon modes can produce dense rf plasmas [62]. Without internal electrodes these rf discharges can produce plasmas in reactive gases for etching of semiconductors [11,63]. When the plasma expands along diverging field lines a double layer is formed which can be used for small thrusters on spacecraft [64].…”

Spatial Profile of Ion Velocity Distribution Function in Helicon High-Density Plasma by Laser Induced Fluorescence Method

“…Additionally, argon ion velocity in plasmas will be shown, depending on the magnetic field gradient in a downstream region by this LIF system. In this discharge, the observed plasma has a narrow, bright blue column, called "Blue Mode", 20,21) which has strong Ar ion emission light intensities for argon plasma. In addition, we have derived a thrust force from these results without active acceleration systems.…”

Plasma source based on helicon discharge for a plasma accelerator

“…These thrusters use different propellants and can be applied as the main, correction, orientation and stabilization engines for geostationary or low-orbit spacecrafts (microsatellites) [1][2][3][4]. Helicon thrusters are also developed to study the processes of interaction of plasma with matter in open magnetic systems and other applications [5][6][7][8][9][10][11][12][13][14].…”