Hannover 2016 – scientific programme

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P: Fachverband Plasmaphysik

P 2: Plasma Diagnostics I

P 2.5: Talk

Monday, February 29, 2016, 12:25–12:40, b305

Design, Setup, and Calibration of a Two-Wavelength Imaging Interferometer for the Diagnostics of Switching Arcs — •Jan Carstensen, Patrick Stoller, Sandor Simon, Philipp Jabs, and René Salzmann — ABB Corporate Research, Baden-Daettwil, 5405, Switzerland

Interferometric, schlieren and shadowgraphy methods, which are sensitive to the refractive index of a gas, are well established flow visualization techniques and have been applied to the diagnostics of electric arcs in high-voltage switching equipment, among many other things. In the vicinity of the arc the interpretation of the results is not straightforward, because the Gladstone-Dale relation, which connects the gas density with the measured refractive index, is not valid for temperatures above 2000 K, and ionization and dissociation processes have to be taken into account. This is a problem in particular during the zero crossing of the current --the moment when the current can be interrupted-- since the hot arcing channel is in a non-equilibrium state, greatly complicating the modeling of the gas composition. One promising approach to tackle this problem is to introduce a second wavelength that allows a direct measurement of the electron density (see Refs. [1,2]). In this contribution we will present our design of a compact and flexible two-color imaging interferometer. The accuracy of the systems is proven using appropriate reference objects and first measurements of an electric arc embedded in a transonic gas flow are presented.

[1] K. Muraoka, et al., Jap. J. Appl. Phys., 19, L293 (1980)

[2] Y. Inada, et al., J. Phys. D, 47, 175201 (2014)