Soft X-ray laser interferometry/shadowgraphy of exploding wire plasmas

• Main Authors: Jankowska, E, Hammarsten, E C, Szapiro, B, Filevich, J, Marconi, M C, Rocca, J J
• Format: Conference Proceeding
• Language: English
• ISSN: 0094-243X

We present the first results from soft X-ray laser interferometry measurements of current-driven thin wire explosions obtained using a capillary discharge pumped 46.9 nm laser and an amplitude division interferometer based on diffraction gratings. We obtained series of high-resolution soft X-ray interferograms/shadowgrams that depict the initial stage of the evolution of exploding Al wires 15 and 25 microns in diameter. The images show a dense vapor core that completely absorbs the probe beam during the initial part of the explosion, and a surrounding plasma shell where both a shift of the interference fringes and partial absorption of the soft X-ray laser probe beam are observed. The excitation of the 25-micron-diameter wires at a current rate of 30 A/ns is observed to result in the uniform expansion. However, an increase of the rate of energy deposited per unit mass is observed to give rise to significant instabilities. The expansion velocity of the wire core was determined from the variation of the measured absorption width of the soft X-ray laser beam. The determination of the electron density and vapor density profile requires the combined analysis of the soft X-ray absorption and fringe shift data.