Search

We have measured and analyzed the second harmonic emission, both in the plane of the laser electric field and perpendicular to it, at several angles near 135° from the laser wave vector. The experiments used from 1 to 80 J of 1.053 μm light to irradiate carbon–hydrogen (CH) targets with a 550 ps pulse. A random phase plate was used, producing characteristic intensities in the range of 1013–1014 W/cm2. This was sufficient to drive the Ion Acoustic Decay Instability, producing Stokes emission well‐separated from the emission spike at the second harmonic of the laser frequency. The spectral structure of the Stokes emission was qualitatively similar for all intensities and angles of observation. The duration of the signals showed trends anticipated from linear theory. To explain the scaling of the signal strength and spectral width requires nonlinear theory.

Indirect-drive implosions experiments were conducted on the Omega Laser Facility to test the performance of uniformly doped plastic ablators for Inertial Confinement Fusion. The first convergent ablation measurements in gas-filled rugby hohlraums are reported. Ignition relevant limb velocities in the range from 150 to 300 μm.ns−1 have been reached by varying the laser drive energy and the initial capsule aspect ratio. The measured capsule trajectory and implosion velocity are in good agreement with 2D integrated simulations and a zero-dimensional modeling of the implosions. We demonstrate experimentally the scaling law for the maximum implosion velocity predicted by the improved rocket model [Y. Saillard, Nucl. Fusion 46, 1017 (2006)] in the high-ablation regime case.