3D Dynamics of a Premagnetized Gas-puff Z-pinch implosion

Abstract

Detailed measurements of the 3D velocity components in an annular magnetized argon Gas-puff Z-pinch implosion driven by the Llampüdkeñ pulse-power generator are presented. The measurements were performed with axial magnetic fields ranging from 0.04 to 0.26 T, generated by magnetic coils placed between the generator electrodes, while the plasma parameters were obtained through a time- and spatially-resolved Collective Thomson Scattering diagnostic along three axes simultaneously. The results show that the recently observed spontaneous rotation produced by applying an axial magnetic field is dependent on both the axial and radial components of the field, and the analysis suggested that the dominant mechanism responsible for this rotation is the Lorentz force $J_z \times B_r$. Additionally, the measurements show that the zippering effect in the pinch can be reduced in the presence of even a small axial field, thereby improving the homogeneity during the stagnation phase.

Figures (13)

• Figure 1: Diagram of the vacuum chamber and the diagnostics used in this work.
• Figure 2: A) View of the Thomson Scattering configuration inside the chamber. B) Cross section of the injector inside the chamber. C) An example of the currents generated by Llampüdkeñ and the x-ray signals measured by the diode for the shots where the applied field was $B_{z0}=0.04$ T. Here we see that the current peaks around 330-340 ns, and that after that the current in all cases is sustained due to current crowbarring. In this case the 0 in the time axis is defined as the moment where the current reaches 10% of its peak value.
• Figure 3: Image of the spectra collected by the north and south fiber bundles taken by the ICCD -18 ns before stagnation for shot n° 1992 using an initial field of 0.19 T. In the right side there is the spectrum measured by the fibers looking at the same volume, where there is a clear difference in $v_k$ between the two fibers caused by the rotation of the plasma that red-shifts the spectrum taken by one fiber and blue-shifts the spectrum taken by the opposite fiber.
• Figure 4: Results for TS and imaging diagnostics for shot n° 1992, using a single-coil configuration with an initial axial field of 0.19 T.
• Figure 5: Results for TS and imaging diagnostics for shot n° 1939, using a double-coil configuration with an initial axial field of -0.26 T.