Comparison of Drive-Seeded Modulations in Planar Foils for 0.35 and 0.53 μm Laser Drive

Laser-speckle-seeded modulations in laser-driven targets have been observed with the Nova laser using 0.53 and 0.35μm drive. The 0.35μm drive produced larger modulations (equivalent to 3.3μm rms surface finish) than 0.53μm drive ( 2.0μm rms). The laser intensity was ~10¹³W/cm², similar to that suggested for directly driven ignition targets during the first several ns. LASNEX simulations of this thermal smoothing effect in both the rms and spectrum agree with the 0.53μm drive data, and are about 15% lower than the measured results with 0.35μm drive.