Optical diagnosis of high pressure non-thermal plasma

Optical diagnosis of high pressure plasma is one of the most powerful tools for investigating chemical reaction mechanisms in the high pressure plasma region. The authors developed various optical measurement systems by using tunable lasers, such as (two-photon-) laser-induced-fluorescence, coherent-anti- Stokes Raman scattering, time evolution of optical emission imaging and others for detecting O-3, O, OH, N, NO* and other radicals in atmospheric pressure plasma. Outline of basic measuring techniques developed by the authors for high pressure plasma diagnosis are explained and real examples of plasma diagnosis are demonstrated in this paper. For example, density distributions of single nitrogen (N) and excited nitrogen molecule (N-2(A)) below the discharge needle generated by the pulse plasma suggest that single N might be generated in the secondary streamer, while N-2(A) might be generated in the primary streamer, and single N decomposes NO more than N-2(A).