Fig. 1. Schematic diagram of the experimental setup; the imaging optical path is divided into three paths, in which the shadowgraph can observe the morphology of the plasma, the interferogram can obtain the electron density of the plasma, and the streak camera can deduce the jet speed. The experiment employed four laser beams positioned on the southern side, each delivering 250 J energy with 1 ns square-wave pulses, which served as the driving sources irradiating the CD planar target.

Fig. 2. (a) Schematic of the expanding plasma on the target surface; laser-target interaction generates plasmas expanding along the target surface. (b) Cross-section of the plasmas generated in the xoy plane, for the detector GOI, where the fringe shift corresponds to the path integral F(y). (c) Cross-section of the plasmas generated in the xoy plane, for the detector OSC, where the fringe shift corresponds to the path integral F (0). (d) For OSC, the fringe shift count D(z, t) at different temporal instances t is determined from measured fringe displacements. Substituting D(z, t) into the Abel inversion formula yields the time-resolved electron density distribution n_e(z, t). For GOI, the 2D fringe shift count D(z, y) at specific time points is acquired through fringe pattern analysis. The Abel inversion formula then allows reconstruction of the spatially resolved electron density profile n_e(z, y).

Fig. 3. Comparison between the numerical solution by the Abel inversion code and the analytical solution.

Fig. 4. (a) Results of the OSC, with the rear edge of the ns square wave as the delay time of zero. (b) Knots appear in the Cu plane target jet at the delay time of 10 ns. (c) Backlit interferogram at 2 ns after the interaction of the laser with the CD planar target. (d) Backlit shadowgraph at 2 ns after the interaction of the laser with the CD planar target.

Fig. 5. (a) Results of the OSC, and the electron density inversion from the region where the fringes bend. (b) Plasma density at different time points was obtained from the OSC fringe by the Abel inversion.

Fig. 6. (a) 2D spatial distribution of the plasma electron density at 2 ns after the interaction of the laser with the CD planar target. (b) Comparison between the plasma electron density obtained by GOI and OSC at 2 ns.