Ion acceleration using temporally-controlled high-intensity laser pulses

Yogo, Akifumi; Daido, Hiroyuki; Mori, Michiaki; Kiriyama, Hiromitsu; Bulanov, S. V.; Bolton, P. R.; Esirkepov, T. Z.; Ogura, Koichi; Sagisaka, Akito; Orimo, Satoshi; Nishiuchi, Mamiko; Pirozhkov, A. S.; Nagatomo, Hideo*; Oishi, Yuji*; Nayuki, Takuya*; Fujii, Takashi*; Nemoto, Koshichi*; Kanazawa, Shuhei; Kondo, Shuji; Okada, Hajime; Nakai, Yoshiki; Akutsu, Atsushi; Shimomura, Takuya; Tanoue, Manabu*; Motomura, Tomohiro*; Nakamura, Shu*; Shirai, Toshiyuki*; Iwashita, Yoshihisa*; Noda, Akira*

The acceleration of protons driven by a high-intensity laser is comprehensively investigated via control of the target density by using ASE just before the time of the main-laser interaction. Two cases were investigated for which the ASE intensity differed by three orders of magnitude: In the low contrast case the beam centre for higher energy protons is shifted closer to the laser-propagation direction of 45, while the center of lower-energy beam remains near the target normal direction. Particle-in-cell simulations reveal that the characteristic proton acceleration is due to the quasistatic magnetic field on the target rear side with the magnetic pressure sustaining a charge separation electrostatic field.