Speaker
Dr
Tsuyoshi Akiyama
(National Institute for Fusion Sceience)
Description
When the electron density of an atmospheric pressure plasma is measured by a conventional interferometer, the phase shifts due to changes of the neutral gas density causes significant measurement errors. A dispersion interferometer, which measures the phase shift arises from dispersion of medium only, can suppress the measured phase shift due to the neutral gas. This is because the dispersion of neutral gases is much smaller than that of a plasma. Hence the dispersion interferometer is sensitive to the plasma only.
In recent years, the CO2 laser dispersion interferometer has been applied to the atmospheric pressure plasmas and its feasibility has been demonstrated [1,2]. The probe beam of the dispersion interferometer is a mixed beam of the fundamental and second harmonic. Since the second harmonic beam is generated with a nonlinear crystal, relatively high power laser was necessary in order to generate the sufficient second harmonic power. This is one of reasons that the dispersion interferometer system is relatively big system. These days, a high efficiency nonlinear crystal OP-GaAs for the CO2 laser becomes commercially available. By using the high efficiency nonlinear crystal, a compact CO2 laser dispersion interferometer, which will be transportable, can be design. In this presentation, the design of such compact CO2 laser dispersion interferometer for atmospheric pressure plasmas will be shown.
[1] K. Urabe, T. Akiyama, K. Terashima, Journal of Physics D: Applied Physics 47, 262001 (2014).
[2] T. Akiyama, R. Yasuhara, K. Kawahata et. al., Journal of Instrumentation 10, P09022 (2015).
Primary author
Dr
Tsuyoshi Akiyama
(National Institute for Fusion Sceience)
