Influence of spatial distribution and temporal dynamics of compressed ICF-target parameters on fast ignition efficiency

The fast ignition as, possibly the most efficient method of inertial confinement fusion (ICF) is based on heating a small fusion initiation region (igniter) while the rest of the target is compressed by a compressing driver. We investigate the influence of two factors on the efficiency of fast ignition of ICF-targets. The first factor is the spatial distribution of thermonuclear-fuel parameters formed due to the ICF-target irradiation by the compressing driver. The second one is a mismatch in the time moments of the target maximum compression and the igniter heating by the igniting driver. The main characteristics of fast ignition, namely, the minimum energy of igniter needed to ignite the main ICF-target fuel (ignition energy) and the burn efficiency (ratio between the burnt and initial fuel masses), are investigated in view of numerical simulation. The scale-invariant dependences of the minimum ignition energy E _ig and the burn efficiency are obtained. It is shown that the burn efficiency depends on the spatial heterogeneity of the thermonuclear-fuel parameters much weaker then the ignition energy, but a strong dependence of the burn efficiency on the mismatch in time moments of the maximum compression and ignition is found. In particular, the ignition before the time moment of the maximum compression is more favorable than the ignition at just this moment.