Generation of tens of GeV quasi-monoenergetic proton beams from a moving double layer formed by ultraintense lasers at intensity 1021-1023 W cm-2

We present a scheme for proton acceleration from a moving double layer formed by an ultraintense circularly polarized laser pulse with intensity 10(21)-10(23) W cm(-2) irradiated on a combination target. The target is composed of a thin overdense proton-rich foil located at the front followed by an underdense gas region behind with an effective Z/A ratio of the order of 1/3. When the areal density of the thin foil is small enough, the protons together with electrons in the thin overdense foil can be pre-accelerated under the laser irradiation. As the laser pulse passes through the thin foil and propagates in the underdense gas region, it excites high-amplitude electrostatic fields moving at a high speed, which appear like a moving double layer. The pre-accelerated protons can get trapped and accelerated in the moving double layer and tens of GeV quasi-monoenergetic proton beams are achieved, provided the laser intensity and plasma density are properly chosen, as demonstrated by one-dimensional (1D) and 2D particle-in-cell (PIC) simulations.