A low-power 2.45 GHz microwave induced helium plasma source at atmosphericpressure based on microstrip technology

A low-power compact 2.45 GHz microwave induced He plasma source operating a t atmospheric pressure for use in atomic emission spectrometry has been dev eloped in microstrip technology. The microstrip plasma (MSP) source for He is fabricated on sapphire substrates. The microstrips are designed for comp act arrangements and for high electric field strengths in the plasma channe l. Both requirements are fulfilled by the high permittivity of sapphire. Th e electrodeless microwave induced plasma (MIP) operates at a microwave inpu t power of 5-30 W (1-10 W in Ar) and gas flows of 50-1000 ml min(-1). It is self-igniting, in the case of He as plasma gas, at atmospheric pressure fo r power levels above 10 W. To demonstrate the excitation capability for non -metals a small amount of HCCl3 vapour was injected into the gas flow and a spectrum of a Cl emission line was observed.