Simulation study of plasma expansion in the early stage of TNSA

For intensities of the PHELIX laser [1] the Target Normal Sheath Acceleration (TNSA) is the most important acceleration mechanism. The ion beams accelerated in this way should be collimated and transported by a solenoid to other accelerator components. In order to optimize the transport and to increase the collimation dedicated simulation studies are needed [1]. The two dimensional phasespace distribution of ions and electrons in the transition regime between the source and the solenoid is still very much unknown. Especially the detailed distribution of the neutralizing electrons. Our task is to develop a model, which describes the phase-space distribution of the generated ions and electrons in two dimensions at μm scale length behind the target. For this we use the VORPAL PIC code [2]. In our 1D simulation we used a 115 fs, 10 W/m laser and a 3μm thick target, ne0 = 2.43×1028 m−3. Although the simple plasma expansion is adiabatic, the very beginning of TNSA can be well described with Mora’s isothermal model [3]. This feature can be explained by the hot electron supply produced by the laser.