Electrical discharges applied in a plasma source for the generation of plasmas can be classified by the frequency of the exciting field. A rough classification is:
- Direct current discharge (DC)
- Pulsed DC discharge (kHz)
- Radio-frequency discharge (MHz) – sustained by two electron heating mechanisms: ohmic heating and stochastic heating
- Microwave discharge (GHz)
- Laser plasma (PHz)
The quality of the coupling of an exciting field of given frequency to a charged particle depends on the position and shape of the plasma resonance. It critically determines the character of the electrical discharge. If the more massive ions cannot follow the oscillating electromagnetic field, the exciting frequency is called high (HF). In this case, the main fraction of the power is transferred to the electrons.
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