Radio frequency matching for helicon plasma sources

Abstract

A theoretical and experimental study of the matching network linking the antenna of a helicon plasma system to its rf power source is described. It is shown that the introduction of a rf step-down transformer into the conventional L-section network has a number of benefits. The transformer increases the reflected antenna impedance seen by the network, bringing it closer to the output resistance of the rf source. The resulting low-Q network is shown to be insensitive to changes in the antenna impedance and the values of the matching elements. It is found that in general only one component in this broad-band network needs to be adjusted rather than the iterative adjustment of two components in the conventional network. The importance of this simplification with respect to the automatic control of the matching network is discussed.

Intermittent transport events in a cylindrical plasma device: experiment and simulation

“…Plasma is produced using a conventional helicon source [25] with a right-handed helical antenna (m = +1) placed around a glass vacuum extension (d = 10 cm), which determines the typical plasma radius r p ≈ 5 cm. The antenna is coupled to a radio-frequency (RF) source (ω RF /2π = 13.56 MHz, P RF ≤ 5 kW) via a capacitive L-matching circuit [26]. All measurements presented here are done with Argon as working gas.…”

Plasma applicators at RF and microwave frequencies

“…The agility requirements for the plasma tuning/matching system has made it necessary to devise smart algorithms that can arrive at the optimal impedance at speeds that can respond to the plasma changes [19,20].…”

Study of a scalable large-area radio-frequency helicon plasma source

“…In the standard configuration, the plasma is produced using a helical m = +1 antenna [15] at the one end of the device. The antenna is placed around a cylindrical glass vacuum extension (d = 0.1 m, l = 0.5 m) and is connected to a RF -source (f RF = 13.56 MHz, P ≤ 4 kW) via a L-matching circuit [16]. The measurements presented here are made with Argon as working gas.…”