Experimental Investigations of the Electrothermal Instability using the Mykonos Linear Transformer Driver*

The electrothermal instability (ETI) has been theorized to amplify density and temperature perturbations on ohmically heated surfaces that compromise magneto-inertial fusion and flyer plate applications. Only recently, facilitated by thin dielectric coatings which suppress plasma formation, has the ETI been demonstrated to exist on thick metal [1]. We present the results of new experimental investigations into the ETI performed in June on the Mykonos LTD, which delivers 850 kA to dielectric-coated 800-um-diameter aluminum rods in approximately 70 ns. Rods were carefully machined with different machining spectra, and several dielectric thicknesses were tested. 12-Frame ICCD imaging, Streaked Visible Spectroscopy and Photon Doppler Velocimetry diagnostics were fielded. These diagnostics permit calculation of surface temperature and early-time radial expansion of the rod surface, as well as ETI growth rates. The experimental setup, collected data, and analysis will be shown.

[1] T.M. Hutchinson, T.J. Awe, B.S. Bauer, K.C. Yates, E.P. Yu, W.G. Yelton, and S. Fuelling. Phys. Rev. E 97 053208 (2018).