Since laser intensity plays an important role in laser plasma interactions,a method of increasing laser intensity- focusing of an intense laser via a parabolic plasma concave surface- is proposed and investigated by three-dimensional particle-in-cell simulations.The geometric focusing via a parabolic concave surface and the temporal compression of high harmonics increased the peak intensity of the laser pulse by about two orders of magnitude.Compared with the improvement via laser optics approaches,this scheme is much more economic and appropriate for most femtosecond laser facilities.
High-order interpolation algorithms for charge conservation in Particle-inCell(PIC)simulations are presented.The methods are valid for the case that a particle trajectory is a zigzag line.The second-order and third-order algorithms which can be applied to any even-order and odd-order are discussed in this paper,respectively.Several test simulations are performed to demonstrate their validity in two-dimensional PIC code.Compared with the simulation results of one-order,high-order algorithms have advantages in computation precision and enlarging the grid scales which reduces the CPU time.
