Field ionization effect on the proton acceleration scheme via high intensity laser interaction with target at different pulse durations

Target Normal Sheath Acceleration (TNSA) mechanism is one of the most common proton acceleration mechanisms in the experimental setup. In this work, the effect of field ionization on the proton acceleration performance in result of the interaction of high intensity laser pulses with different pulse lengths was studied using two-dimensional particle in cell (PIC) simulations. For this purpose, two solid (neutral) targets as well as fully ionized plasma target, made of aluminum layer with thickness of 0.5 μm, and paired with a thin layer of hydrogen with thickness of 50 nm are considered.  Simulation results showed that considering the constant pulse energy and a medium laser intensity (here a0 =10 for pulse width of 25 femtoseconds) the use of solid structure leads to an increase in the maximum energy of the protons by about 36%. In addition, the difference in proton cut-off energy between the solid target and the ideal plasma one decreases with increasing the laser pulse width.