Study On The Method Of Microwave Resonator Probe For Atmospheric Pressure Plasma Jet

Atmospheric pressure plasma jet (APPJ) has been widely applied in material processing and biomedical application, as due to it non-thermal and reactive properties. But there are few studies on its parameters diagnostics. This article focuses on the diagnostic method of atmospheric plasma jet using the microwave resonator probe, this method is based on the transmission line theory, using the related parameters of reflection resonance spectrum to calculate the electron density of plasma.To optimize the probe and choose the best structure of probe were the first things. For coaxial microwave resonance probe, we adopted two kinds of schemes, one way was to change the shape of the inner conductor of probe, the straight cylinder changed into the shape of spiral, by changing the length of the inner conductor, as far as possible to minimize the length of the probe, so that the plasma inside of the probe was more uniform, the measurement results were more accurate; the other way was to add a magnetic circle at the bottom of the coaxial probe, can be seen from the simulation results, after adding medium ring, the value of Q was increased. When the permeability is10, the relative dielectric constant is10, conductivity is10000s/m, the value of Q was the largest. The influence of the geometry size of hairpin probe、the turns of coupling coil、the position relationship between probe and coupling coil to the value of Q were discussed.Secondly the problem of discharge metal interference with the resonance of probe was discussed. When the probe was positioned below the discharger metal, the value of Q was significantly reduced, the causes of this phenomenon was analyzed, through combining theory with practice, we fond the solution.The last, the relationship between the reflection resonance spectrum of probe and the density of plasma jet and the calculation of electron density were studied. The experimental results showed that the full width of half maximum of resonance spectrum is proportional to the electron density, namely the full width of half maximum become wider with the electron density increased. According to the formula of electron density which based on the theory of the transmission line, we can calculate the electron density. When the RF powers were60W and100W, the electron density were obtained. Through the analysis, the results were reasonable.