Proton Acceleration Enhancement in Frequency Chirped Laser Pulse Interaction with Plasma

Proton acceleration process by the generated sheath in the rear-side of an Al target in the interaction of P polarized laser with the pulses duration of  ≥40 fs and intensity of 3.6×1019 W cm-2 has been experimentally and  numerically studied. The results show that by employing the positively chirped pulse, the proton cut off energy and the number of the accelerated protons are increaesd in comparison with an unchirped and negatively chirped pulse interactions. After that, the electron heating process in interaction of positivly and negativly chirped  pulse is investigated and correlation between the chirped parameter and produced electrostatic field in the backside of the target is studied. Particle- in-cell simulation results show that the electron heating process and consequently the electrostatic field for proton acceleration goal are significantly increased by employing the positively chirped pulse campared to negativly unchirped conditions.