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

A low-power compact 2.45 GHz microwave induced He plasma source operating at atmospheric pressure for use in atomic emission spectrometry has been developed in microstrip technology. The microstrip plasma (MSP) source for He is fabricated on sapphire substrates. The microstrips are designed for compact arrangements and for high electric field strengths in the plasma channel. Both requirements are fulfilled by the high permittivity of sapphire. The electrodeless microwave induced plasma (MIP) operates at a microwave input 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 for 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.