Numerical simulation of filamentation for spatially smoothing beam in hohlraum

Three dimensional models of spatially smoothing beam propagating in hohlraum are established in a laser plasma simulation code named LAP3D to investigate laser filamentation. Simulation results of spatially smoothing beam produced by continuous phase plates (CPP) with a given f number (f=11) propagating in a 2000 laser wavelength long homogeneous slab plasma, corresponding to plasma density at tenth of the critical density, electron and ion temperature at 3 and 1 keV, respectively, are presented in this paper. The influence of parameters associated with the beam power and intensities on developing of laser filamentation instability is analyzed. Features of laser filamentation instability are found with simulation results, including beam spay and laser energy spreading to higher wave numbers in the Fourier space. It is found that there is a clear correlation between onset of the beam filamentation and the value of the average laser intensity. Based on simulation results, it is suggested that with high hot spot intensities, bigger size hot spots or other smoothing methods should be applied to suppress laser filamentation.