Generation of a low-power capacitively coupled plasma at atmospheric pressure

An RF generator (13.56 MHz) for maintaining an atmospheric capacitively coupled plasma is presented and studied. The most important of its characteristics is that the plasma is an intrinsic part of the resonant circuit of the radiofrequency oscillator. Due to this special feature, the plasma can be maintained at the low levels consumed power (40-80 W) in air, argon, or a mixture of them. The plasma can be used as an atomization and excitation source. Two plasma torches are presented: the first one is to introduce liquid samples into the plasma and the second one is for direct analysis of nonconductive solid samples. Some electrical parameters of the plasma were measured, including plasma power, plasma resistance, and the level of the noise voltage.