Variation of the ion line density at the array axis with time for MAGPIE and COBRA. Horizontal line indicates critical ion line density for precursor column formation, and vertical lines indicate precursor formation times for MAGPIE (measured) and COBRA (predicted).
Current pulses for MAGPIE and COBRA, along with running integral of the square of the current pulse.
Sequence of gated self-emission images for W loads in COBRA showing formation dynamics of the precursor column.
Lineouts across Al and W arrays at 100 and 104 ns, respectively, showing broad early time emission profiles.
Correlation of the peak in the radiation signature to the observation of the precursor column on the optical streak images for a W array on COBRA.
Variation of emission diameter during column formation for Al array on COBRA.
Plot of diameter variation of precursor column during formation for (left) Al and (right) W arrays on both MAGPIE and COBRA using axes normalized to the time of formation and minimum diameters in each case (put Al/W labels on plots).
Laser shadowograms of W arrays from (left) COBRA at 150 ns and (right) MAGPIE at 160 ns showing formation of the precursor column initially at the anode in both cases.
Streak image and magnification of a W load on COBRA showing plasma structure around precursor column formation time.
Radiographs with areal density lineouts for (upper) W (150 ns) and (lower) Al (130 ns) arrays on COBRA.
plots of the precursor column mass density as a function of time compared to the rocket model.
Radiograph and lineouts of W axial flares on COBRA (0.5 mm from wire position).
(Top) XUV spectra from Al arrays on (upper) COBRA (time integrated) and (lower) MAGPIE [time gated at precursor column formation (Ref. 54)], with (bottom) spectral lineouts of each.
Variation in precursor column formation time with ablation velocity assumed for COBRA current drive. Dotted line indicates giving formation time of 107 ns.
Full array with radiographs along with magnified sections indicated by black box of (a) side on large Al wire cores (COBRA, 120ns, 110% rise time), (b) rear of same on MAGPIE (197 ns, 79% rise time), and (c) typical small Al wire radiograph from MAGPIE (220ns, 88% rise time).
Plots of axial density variation as a function of array radius calculated from a two-velocity rocket model (see text) for (left) 8 mm radius array on MAGPIE at 160 ns, and (right) 10 mm radius array on Z at 100 ns.
Summary of precursor column characteristic on MAGPIE and COBRA along with analytical predictions for COBRA.
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