1:45 PM - 2:00 PM
△ [17p-C204-3] Diagnostics of microwave discharge low-pressure argon plasma by multi-optical emission line analysis based on collisional-radiative model
Keywords:low-pressure plasma diagnostics, optical emission spectroscopic measurement, collisional-radiative model
Line-pair method cannot be applied to wide-range electron temperature Te and density Ne diagnostics of plasmas in the state of non-equilibrium. Although the method using multi-emission lines is suitable, little has been reported for the low-pressure plasma measurement. We proposed the optical emission spectroscopic (OES) diagnostic method for the low-pressure argon plasma. In this presentation, the applicability for the microwave discharge argon plasma is reported.
Based on the Ar collisional-radiative (CR) model, the dominant elementary possesses were extracted for the excitation kinetics for several excited states. And, the excitation-kinetic model for the OES diagnostics was established. As a result, the diagnostic model was obtained. In the model, input parameter is 15 optical emission lines (wavelength range: 340.7 – 912.5nm). Possible measurement range is 1.0 ≤ Te [eV] ≤ 3.8, and 1.0 × 109 ≤ Ne [cm-3] ≤ 5.0 × 1012.
In order to examine the validity of the proposed method, microwave discharge argon plasma was diagnosed with (A) probe measurement: (A-1) under the assumption that the electron density distribution function (EEDF) is Maxwellian, (A-2) together with the measurement of the EEDF by the Druyvesteyn’s method, and equivalent Te measurement; and (B) OES measurement by the present proposed method at points (from the center of the waveguide) = 10, 14, and 18 cm, with the microwave power = 100, 300, and 500 W.
Concerning Ne diagnosis, the trend of Ne determined with the scheme (B) was in good agreement with the scheme (A-1). Meanwhile, as for Te diagnosis, it was difficult to evaluate, because the result of the scheme (B) reached the limit value of root-finding range in the numerical procedure. However, at least, the result of (A-1) is considered to be reasonable. And by using input with arbitrary shaped EEDF is measured by the OES measurement, and the resultant improvement of the diagnostic result can be expected.
Based on the Ar collisional-radiative (CR) model, the dominant elementary possesses were extracted for the excitation kinetics for several excited states. And, the excitation-kinetic model for the OES diagnostics was established. As a result, the diagnostic model was obtained. In the model, input parameter is 15 optical emission lines (wavelength range: 340.7 – 912.5nm). Possible measurement range is 1.0 ≤ Te [eV] ≤ 3.8, and 1.0 × 109 ≤ Ne [cm-3] ≤ 5.0 × 1012.
In order to examine the validity of the proposed method, microwave discharge argon plasma was diagnosed with (A) probe measurement: (A-1) under the assumption that the electron density distribution function (EEDF) is Maxwellian, (A-2) together with the measurement of the EEDF by the Druyvesteyn’s method, and equivalent Te measurement; and (B) OES measurement by the present proposed method at points (from the center of the waveguide) = 10, 14, and 18 cm, with the microwave power = 100, 300, and 500 W.
Concerning Ne diagnosis, the trend of Ne determined with the scheme (B) was in good agreement with the scheme (A-1). Meanwhile, as for Te diagnosis, it was difficult to evaluate, because the result of the scheme (B) reached the limit value of root-finding range in the numerical procedure. However, at least, the result of (A-1) is considered to be reasonable. And by using input with arbitrary shaped EEDF is measured by the OES measurement, and the resultant improvement of the diagnostic result can be expected.