2D PIC Simulation of Electron Acceleration in Interaction of Short Laser Pulse with Plasma Having a Density Ramp in Bubble Regime

In this paper, using 2D PIC simulation, the electron acceleration in the bubble regime has been investigated in the interaction of a short high-power laser pulse with an underdense plasma with a density ramp. Due to the laser pondermotive force, a plasma wave and its corresponding electric field are formed in the plasma. The electrons injected in the focusing and acceleration region of the plasma wave field can get energy from the wave and are accelerated to high energies of the Giga-electron-Volt range. The simulation results show that with increasing the plasma density gradient, the phase speed of the generated plasma wave increases, and the corresponding wavelength decreases. This causes the displacement of the plasma wave focusing and acceleration region and ultimately increases the acceleration length in the acceleration process. Considering a laser pulse with dimensionless intensity amplitude , pulse duration , and plasma with density ramp length ,the plasma wave accelerating electric field with amplitude was generated. The results of this work can be crucial in choosing an appropriate plasma profile to design the laser-plasma accelerator system for obtaining the Giga-electron-Volt energy gain in a short time.