Effects of a Preembedded Axial Magnetic Field on the Current Distribution in a Z -Pinch Implosion

Stable and unstable supersonic stagnation of an axisymmetric rotating magnetized plasma

“…In many cases, an external axial magnetic field is applied to stabilize the implosion or provide the 'magneto-thermo-insulation' (Lindemuth & Kirkpatrick 1983) of the stagnated plasma, which is the critical issue for all approaches to magnetized target fusion and magneto-inertial fusion (Turchi 2008;Garanin 2013;Wurden et al 2016;Lindemuth 2017), including the MagLIF. The axial magnetic field, in turn, can affect the implosion dynamics in various ways, not all of which are fully understood; see Felber et al (1988), Shishlov et al (2006), Rousskikh et al (2017), Mikitchuk et al (2019), Conti et al (2020), Seyler (2020) and references therein. Recent experiments with gas-puff Z-pinch implosions in an external magnetic field (Cvejić et al 2022) demonstrated a self-generated rotation of the imploding axisymmetric plasma.…”

Observation of fast current redistribution in an imploding plasma column

“…A few experimental studies have measured the timedependent magnetic field radial distribution in the imploding Z-pinch plasma [22][23][24][25]; those that were performed at the time of stagnation [24][25][26], outside the SP but close enough to it, confirmed the flow of only a small fraction of the current in this plasma. However, in the present work, the temporal evolution of the current density radial distribution was determined down to the small radius of the SP and, in particular, with a high spatial resolution.…”

“…The experimental system used an initial gas column with a radial distribution that provided a peak density on axis, thus allowing for satisfactory reproducibility and symmetry due to the mitigation of the Magneto-Rayleigh-Taylor instabilities [27,28]. The diagnostics, based on Zeemanpolarization spectroscopy, allowed for determining B θ , even when the Zeeman-split pattern was fully obscured by the line broadening [22][23][24][25]29]. Also, the radial distribution of charge states in the plasma was measured, as in [22,24,25], and was used to obtain B θ as a function of r from the chordal measurements without the need to inverse Abel transform the observed line shapes (i.e.…”

“…The fast current redistribution might also bear relevance to general pulsed-power systems, such as plasma switches [12][13][14] or transmission lines [15,16]. In these systems, undesired plasmas of various properties can be produced due to different sources, such as electrodes [15,16], instabilities [41,42], evaporation in solid loads [43], boundary layers in gas loads [30], and unimploded plasma in Z-pinches [23]. Considering the various mechanisms that can lead to a fast current redistribution, as discussed here and in [37] based on analytic models and simulations, the presence of such plasmas might thus affect the operation of many laboratory plasmas.…”

“…Considering the various mechanisms that can lead to a fast current redistribution, as discussed here and in [37] based on analytic models and simulations, the presence of such plasmas might thus affect the operation of many laboratory plasmas. Further experimental investigations of the current switching should help in developing methods to control it, and thus to achieve higher efficiency in current-pulse transmission and in producing higher energy-density plasmas [23]. Due to the fundamental aspects of this phenomenon it can also be relevant for the investigations of space plasmas [44,45], as well as the evolution of the current distribution and energy balance in fusion plasmas [5,10,20].…”