“…During the past two decades, several laser-based ion acceleration mechanisms have been proposed, 2,4 including target normal sheath acceleration (TNSA), 7,8 radiation pressure acceleration (RPA), 9,10 breakout afterburner acceleration, 11,12 collisionless shock acceleration, [13][14][15] Coulomb explosion acceleration, 16,17 and others 18 or their combination. [19][20][21][22] A large number of theoretical, numerical, and experimental results indicate that RPA using nanometer-thick ultrathin foil target is one of the important mechanism for the generation of quasi-monoenergetic GeV ion beams at relatively high laser intensities. 9,10,[23][24][25][26][27] In RPA, it is favorable to use circularly polarized (CP) relativistic laser pulses to avoid the foil destruction originating from undesired electron heating induced by the oscillating part of the ponderomotive force of the linearly polarized (LP) laser pulse, 4,[28][29][30] that is Àðe 2 =4m e x 0 2 Þ Â cosð2x 0 tÞrE 2 ðyÞ.…”