A two-phase proton acceleration scheme using an ultra-intense laser pulse irradiating a proton foil with a tenuous heavier-ion plasma behind it is presented. The foil electrons are compressed and pushed out as a thin dense layer by the radiation pressure and propagate in the plasma behind at near the light speed. The protons are in turn accelerated by the resulting space-charge field and also enter the backside plasma, but without the formation of a quasistationary double layer. The electron layer is rapidly weakened by the space-charge field. However, the laser pulse originally behind it now snowplows the backside-plasma electrons and creates an intense electrostatic wakefield. The latter can stably trap and accelerate the pre-accelerated proton layer there for a very long distance and thus to very high energies. The two-phase scheme is verified by particle-in-cell simulations and analytical modeling, which also suggests that a 0.54 TeV proton beam can be obtained with a 10 23 W/cm 2 laser pulse.

In this paper, we studied the effect of decarburization layer thickness and carbon content on the ultimate cold bending angle of the hot stamping steels. The ultimate cold bending angle of hot stamping steel with 0.23 (wt. pct) carbon content and 0.35 (wt. pct) carbon content is compared. With the increase of carbon content, the ultimate cold bending angle decreases from 66.1°to 40.8°. The appearance of a completely decarburized layer in the microstructure will significantly increase the ultimate cold bending angle, from 66.1°to 77.4°. It can be found that carbon content is key factor affecting the ultimate cold bending angle of hot stamping steels, the thickness of the decarburized layer is another key factor affecting the ultimate cold bending angle of the hot stamping steels.