The explosion dynamics of very large (approximately 10(6)-10(7) atoms) deuterium clusters irradiated by ultraintense laser pulses (I approximately 10(18) W/cm(2)) is analyzed self-consistently with one-to-one three-dimensional and two-dimensional fully relativistic particle-in-cell simulations. Small-scale shock shells in the expanding ion cloud are observed. A technique to induce the formation of large shock shells inside a single cluster, increasing the probability of intracluster nuclear reactions, is proposed and demonstrated.

The ion phase-space dynamics in the Coulomb explosion of very large ͑ϳ10 6 -10 7 atoms͒ deuterium clusters can be tailored using two consecutive laser pulses with different intensities and an appropriate time delay. For suitable sets of laser parameters ͑intensities and delay͒, large-scale shock shells form during the explosion, thus highly increasing the probability of fusion reactions within the single exploding clusters. In order to analyze the ion dynamics and evaluate the intracluster reaction rate, a one-dimensional theory is used, which approximately accounts for the electron expulsion from the clusters. It is found that, for very large clusters ͑initial radius ϳ100 nm͒, and optimal laser parameters, the intracluster fusion yield becomes comparable to the intercluster fusion yield. The validity of the results is confirmed with three-dimensional particle-in-cell simulations.