We investigate the basic physics of a small-scale (initial diameter ~ 3 mm) z-pinch implosion. Besides the important fundamental physics of the studied configuration, this research is motivated by its potential application as a waveguide in laser particle accelerators [1] and as a compact radiation source for lithography [2].

In the present experiment, a peak current of up to 27 kA with a rise time of 160 ns is driven axially through an oxygen column. The current ionizes the gas and generates an azimuthal magnetic field that compresses the plasma radially. The plasma dynamics and its interaction with the magnetic field are still not well understood. In particular, experimental data on the current distribution in the plasma, which is a key parameter in the implosion, is scarce. Here, we present a comprehensive investigation of the imploding plasma by means of time and space resolved spectroscopy. Particularly challenging is the measurement of the azimuthal magnetic field in the present plasma parameters (~10¹⁸ cm³, 5 - 13 eV), as the large Stark broadening of the spectral lines smears out the Zeeman-splitting pattern [3, 4]. This challenge was met by employing a spectroscopic technique based on the polarization properties of the Zeeman components. This approach allows for simultaneous determination of the azimuthal magnetic field and the electron density (from Stark broadening) and temperature (from line intensity ratios). These data enable to reconstruct a comprehensive picture of the mechanism of the plasma compression.

[1] W. Leemans, B. Nagler, A. Gonsalves, C. Toth, K. Nakamura, C. Geddes, E. Esarey, C. Schroeder, and S. Hooker, Nature Publishing Group, 2 (2006)

[2] W. Neff, K. Bergmann, O. Rosier, R. Lebert, and L. Juschkin, Contrib. Plasma Physics, 41 (2001).

[3] G. Davara, L. Gregorian, E. Kroupp, and Y. Maron, Phys. Plasmas 5 (1998)

[4] R. Doron, D. Mikitchuk, C. Stollberg, G. Rosenzweig, E. Stambulchik, E. Kroupp, Y. Maron, and D. A. Hammer, High Energy Density Phys. 10 (2014)