  We demonstrate in this research the quasi-monoenergetic electron and proton
acceleration through three dimensional particle-in-cell simulations of short
petawatt circular polarized laser pulse interactions with near critical density
hydrogen target. We numerically show that under controlled choice of laser and
target parameters, the high energy electrons and protons can be illustrated in
experiment at advanced high power laser facilities eg ELI - ALPS. We detailed
the microphysics involved in the acceleration mechanism, which required
investigating the role of plasma density gradients, plasma density, and target
thickness. The role of selfgenerated plasma electric and magnetic fields is
depicted on proton energy and density distribution. We numerically investigate
here the laser driven proton acceleration where energetic protons with energies
more than 200 MeV and charge in excess of 10 nC and conversion efficiency more
than 6 percent (which implies 2.4 J proton beam out of the 40 J incident laser
energy). Additionally and interestingly, we show from simulation study first
time the quasi-monoenergetic ring shaped electron beam driven by circularly
polarised laser which may prove useful for plasma based-based X-ray source and
collimation of positron beam.
