Role of hot-electron preheating in the compression of direct-drive imploding targets with cryogenic D2 ablators

The compression of direct-drive, spherical implosions is studied using cryogenic D(2) targets on the 60-beam, 351-nm OMEGA laser with intensities ranging from similar to 3x10(14) to similar to 1x10(15) W/cm(2). The hard-x-ray signal from hot electrons generated by laser-plasma instabilities increases with laser intensity, while the areal density decreases. Mitigating hot-electron production, by reducing the laser intensity to similar to 3x10(14) W/cm(2), results in areal density of the order of similar to 140 mg/cm(2), in good agreement with 1D simulations. These results will be considered in future direct-drive-ignition designs.