Design of long focal-depth optical element for plasma diagnostic system in ICF drivers

For the laser plasma diagnostic system in the inertial confinement fusion(ICF) drivers, the logarithmic axicon was adopted and improved by fifth-order super-Guassian edge smoothing, centre apodization and choosing suitable device parameters. The simulation experiments indicated that, to obtain a long-focal depth, small focused spot, small side lobe and homogeneous intensity focused beams in the on-axis and transverse directions, the focal depth of the logarithmic axicon should be 3~5 mm, the apodization radius should be 15~60 mm, and the edge super-Guassian smoothing order should be 5. The long focal depth device whose focal depth was more than 3 mm, axial intensity distribution was uniform and the maximal relative intensity of the side lobe was less than 2% of the center intensity was des