Lateral movement of a laser-accelerated proton source on the target's rear surface

Nakamura, Tatsufumi; Mima, Kunioki*; Ter-Avetisyan, S.*; Schnrer, M.*; Sokollic, T.*; Nickles, P.*; Sandner, W.*

The spatial dependence of proton acceleration at the rear surface of a target which is irradiated by high contrast and ultra-intense laser pulses is investigated. Lateral movement of proton acceleration position at the rear surface is observed, which is proofed by two-pinhole measurement which results in the observation of protons with narrow energy band. This drifting is uniquely observed when relativistic intensity laser pulses irradiate targets with small pre-plasma with oblique incidence, which is confirmed by 2D-PIC simulations. This proton acceleration scenario by the fast moving sheath field leads to the energy selection of accelerated protons as a function of observing position.