Generation of Ultrahigh-Velocity Ionizing Shocks with Petawatt-Class Laser Pulses

Ultrahigh-velocity shock waves ($\sim 10000\mathrm{km}/\mathrm{s}$ or $0.03c$) are generated by focusing a 350-TW laser pulse into low-density helium gas. The collisionless ultrahigh-Mach-number electrostatic shock propagates from the plasma into the surrounding gas, ionizing gas as it becomes collisional. The shock undergoes a corrugation instability due to propagation of the ionizing shock within the gas (the Dyakov-Kontorovich instability). This system may be relevant to the study of very high-Mach-number ionizing shocks in astrophysical situations.

Figure 1

(a) Experimental setup. (b) Front images in helium plasma interactions with $n_e=1.6\times {10}^{19}{\mathrm{cm}}^{-3}$ and 350-TW, 1-ps-duration laser pulses. The white line indicates the focal plane of the laser. The laser propagates left to right. (c) Temporal evolution of the front radius.

Figure 2

(a) Front images in helium plasma interactions with $n_e=2.0\times {10}^{19}{\mathrm{cm}}^{-3}$ using 200-TW, 1-ps-duration laser pulses. The white line indicates the focal plane of the laser. The laser propagates left to right. (b) Temporal evolution of the front radius and (c) front thickness along the radial axis defined by the laser focal plane.

Figure 3

(a) Images of the rippled front structure at $t=t_0+233\mathrm{ps}$ and the smooth front structure at $t=t_0+70\mathrm{ps}$ with $n_e=2.0\times {10}^{19}{\mathrm{cm}}^{-3}$ and 200-TW, 1-ps-duration laser pulses. (b) Front image with $n_e=2.0\times {10}^{19}{\mathrm{cm}}^{-3}$ and 200-TW, 1-ps-duration laser pulses taken at $t=t_0+(800\pm 200\mathrm{ps})$.

Figure 4

OSIRIS code results for different time steps showing (a) the evolution of electron density and (b) the magnitude of the radial electric field.