(color online) (a) Interferogram of the plasma cloud without the obstacle, taken at a delay time of 3 ns. The purple arrows represent the main laser pulses. The white line indicates the original position of the CH planar target. (b) Abel inverted density map of the red box region in panel (a). (c) Shadowgraph and (d) interferogram taken at the delay time of 3 ns with the obstacle. (e) Shadowgraph and (f) interferogram taken at the delay time of 1 ns with the obstacle. The blue solid circle indicates the cross section of the obstacle.