Observation of proton modulations in laser–solid interaction

Abstract

We report an experimental investigation on the proton acceleration from the interaction of intense
laser pulse of intensity about 10^20 Wcm−2 with a thin foil of Aluminum, Titanium and Gold of
thickness 2μm. Protons are accelerated via the TNSA mechanism from the rear surface of the target
and in addition, protons accelerated from the front surface were also detected on the Radio Chromic
films. Hollow proton rings could be seen on the radio chromic films corresponding to 1-3MeV protons.
The protons from the front surface are driven into the target and directed towards the rear side of
the target by the Kilotesla magnetic fields generated from the laser-plasma. The enhancement in
the proton number in the 1-3MeV range with a hollow beam profile in the experiments are in good
agreement with the observed strong magnetic field structures from the results of 2D Particle-In-Cell
simulations EPOCH and SMILEI.