Technical plasma can be excited at atmospheric pressure or in diluted gases. Excitation at atmospheric pressure is carried out by gas discharge. Due to the free path of the ions at atmospheric pressure (approx. 10-7 m), the expansion of the plasma is restricted to the zone with very high field strength. Low-pressure plasma is generated between two electrodes by electromagnetic high-frequency fields. Because of the long free path of excited particles (approx. 10 cm with 10-3 mbar), the excitation of the plasma can also go beyond the active range of the high-frequency field and can comprise the entire volume of a vacuum chamber. erfassen. Generally, low-pressure plasma can be excited in any gas. angeregt werden. Also substances which are liquid at atmospheric pressure can be gaseous at low pressure, so that they can be used as a process gas. verwendet werden. They are evaporated outside of the vacuum chamber and supplied in their gaseous state. The large number of suitable process gases means that correspondingly multifaceted plasma processes can be realised.