在施加微波時，微波的電磁場會沿電漿與介電材質管柱間的介面做縱向傳播（此時電漿彷彿是導體般），此時電漿會生成於電漿源中的介電材質管柱中，我們稱此為表面波電漿。表面波電漿的優點在於不需要在電漿源內設置電極（可減少污染）、氣體壓力區間寬（1x10^-4 Torr 到大氣）、頻率範圍廣（27MHz ~ 10GHz），再加上其電漿溫度高、氣體解離能力強，因此在製程廢氣減排（gas abatement）或是氣體反應（gasification）的應用具備極高的潛力，是環保綠色科技發展的重要技術。

S-Wave is a compact plasma torch designed for industrial and laboratory applications from 10-2 mbar to atmospheric pressure.

The plasma is created in a dielectric tube placed inside the source. The microwave electric field propagates longitudinally at the dielectric/plasma interface (plasma behaves as an electrical conductor). Radially the wave is strongly attenuated at skin depth.

This principle allows to create and sustain plasma columns with lengths which depend on the operating pressure, microwave power and gas nature. The S-Wave plasma source is inductively coupled, thus only two tuning adjustments are provided to match the impedance.

Generally, nearly 0 % of reflected power is achieved using the integrated tuners. In addition, for given operator-set discharge conditions, the plasma is fully reproducible without any need for retuning at start-up.

This surface wave plasma source works at 2,45 GHz and generates plasma in dielectric tubes placed in a standard WR340 waveguide. It enables the ignition and sustaining of long plasma columns depending on the pressure, the microwave power and the nature of the gas.

The Downstream plasma source is ideal for working at pressures in the millibar range or to atmospheric pressure, with dielectric tube diameters between 30 and 50 mm. At atmospheric pressure, a vortex injection system and a plasma ignition system are provided. The plasma source can operate at 10 kW without time limitation at atmospheric pressure.

Potential Application for Downstream Plasma Source: Gasification and Gas Abatement 

Gasification allows the conversion of organic carbonaceous materials, fossil fuel and biomass into syngas such as CO, H2 and CO2. Combustion of syngas obtained from biomass is considered to be a source of renewable energy. Both gas abatement and gasification require high temperatures which can be achieved thanks to microwave plasma.