Plasma Jets Driven by Ultraintense-Laser Interaction with Thin Foils

Experimental evidence of plasma jets ejected from the rear side of thin solid targets irradiated by ultraintense ($>{10}^{19}\mathrm{W}{\mathrm{cm}}^{-2}$) laser pulses is presented. The jets, detected by transverse interferometric measurements with high spatial and temporal resolutions, show collimated expansion lasting for several hundreds of picoseconds and have substantially steep density gradients at their periphery. The role played by radiation pressure of the laser in the jet formation process is highlighted analytically and by extensive two-dimensional particle-in-cell simulations.

Figure 1

Interferograms obtained at (a) expt-1 and (c) expt-2 for $3\mu \mathrm{m}$ Al and $5\mu \mathrm{m}$ Cu foil targets, respectively. The interferograms were taken at 250 and 400 ps, respectively, after the arrival of the CPA on target. Spatial scales shown in the images correspond to the scales in the object plane. The inverted electron density profile contour plots (in the unit of ${10}^{21}{\mathrm{cm}}^{-3}$) of the rear side plasma are shown next to the respective intergerograms [(b),(d)]. $(Y,Z)=(0,0)$ corresponds to the point of CPA interaction with the target.

Figure 2

(a) Interferogram taken at 400 ps after the arrival of CPA on $20\mu \mathrm{m}$ Cu foil in expt-2. The spatial scale mentioned in the image corresponds to the scale in object plane. (b) The inverted electron density profile contour plots (in the unit of ${10}^{21}{\mathrm{cm}}^{-3}$) of the rear side plasma obtained from the interferogram. (c) Comparison between the on-axis electron density profile shown in (b) (red or gray) and Fig. 1d (black).

Figure 3

Results obtained from 2D PIC simulation. (a) Ion density distribution in the $x$, $y$ plane at $t=1.7\mathrm{ps}$; (b) the $z$ component of the magnetic field distribution in the $x$, $y$ plane at $t=1.35\mathrm{ps}$. Phase plane view graphs for (c) ($Px$, $x$), (d) ($Px$, $y$), and (e) ($Py$, $y$) at $t=1.2\mathrm{ps}$.