The initial imprint of mass perturbation due to spatial nonuniformity of la
ser intensity is one of the most important issues in laser fusion research.
Several imprint mitigation schemes by the use of soft X-ray radiation have
been proposed to enhance the thermal smoothing effect within the conductio
n region. One of the schemes uses external X-ray irradiation prior to laser
incidence to produce preformed plasma. Another has a low-density foam laye
r and high-Z material to heat the foam radiatively and make it uniform in d