Effects of radiation on direct-drive laser fusion targets

The role played by radiation in the radiation-preheated direct-drive laser fusion target design is discussed. The soft x-rays emitted during the foot of the laser pulse-at a few 10(12) W/cm(2)-preheat the low-opacity foam abl ator which helps to control the Rayleigh-Taylor instability. The foam opaci ty is, however, thick enough to stop that radiation, keeping the fuel on a low adiabat. Radiation effects are also important in the blow-off corona of the target because they establish a long scale-length plasma. This may hel p to shield the ablation region from the nonuniformities in the laser absor ption. (C) 2000 American Institute of Physics. [S1070-664X(00)92905-7].