Local optical spectroscopy of transformer coupled plasma using a Parallel hord optical probe

A motor driven optical probe consisting of an optical fiber, a small achromatic bi-convex lens and an optical vacuum feed through has been developed. The optical field of view of the probe is designed to have a parallel chord along the moving direction, so it can provide the local plasma parameters. We have generated the TCP (Transformer coupled plasma) with Ar gas and compared the spectral data obtained from the optical probe. Integrated optical emission intensity was measured along the radial direction of TCP. The radial emission intensity distribution can be easily obtained by spatially differentiating the integrated intensity. The experiment showed reliable results in comparison with that of Langmuir probe. Also, from the rf power and gas pressure dependence of the emission intensity, the experimental results are well adapted with theoretical consideration. This optical technique of measuring the local emission properties will be very useful for the analysis of radicals, reactive species, gas composition, and electron density in a low temperature plasma diagnostics.