Development of single-plate, two-wavelength Mach Zehnder interferometer for the measurement of unsteady density field with ionization

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A new Mach-Zehnder interferometer, in which two interferograms with different wavelengths are imaged onto a single plate, has been developed. As light sources, semi-conductor lasers with the respective wavelengths of 473 nm and 593 nm are used. A dual-band-path filter is used to eliminate the effect of emission from ionized gas.The two-dimensional density distributions of heavy particles and electrons are obtained through digital data processing. Demonstration measurement was conducted with laser-pulse-generated plasma in a chamber of 350 mm in diameter and 400 mm in length, thereby obtaining a heavy particle density of 5×1025m-3and a degree of ionization of 10 % in the axi-symmetric field.