Inductively coupled plasmas are formed by coupling energy produced by a RF generator to the plasma support gas with an electromagnetic field.
The field is produced by applying an RF power (typically 700-1500 W) to an antenna (load coil) constructed from 3-mm-diameter copper tubing wrapped in a two- or three-turn 3-cm-diameter coil, positioned around the quartz torch assembly designed to configure and confine the plasma.
An alternating current field is created that oscillates at the frequency of the tuned RF generator. The plasma is initiated by the addition of a few "seed" electrons, generated from the spark of aTesla coil or a piezoelectric starter, to the flowing support gas in the vicinity of the load coil.
After the plasma is initiated it is sustained by a process known as inductive coupling. As these seed electrons are accelerated by the electromagnetic RF field, collisions with neutral gas atoms create the ionized medium of the plasma.
The mean free path of accelerated electrons in atmospheric pressure argon gas is about 1 um before a collision occurs with an argon atom. These collisions produce additional electrons.This cascading effect creates and sustains the plasma.
Once the gas is ionized, it is self-sustaining as long as RF power is applied to the load coil. The ICP has the appearance of an intensely bright fireball-shaped discharge.
Once the gas is ionized, it is self-sustaining as long as RF power is applied to the load coil. The ICP has the appearance of an intensely bright fireball-shaped discharge.
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