Impact ignition is a new scheme of laser fusion different from the central
ignition and fast ignition, and is expected to be another path toward high
gain. In this scheme, Petawatt laser is not necessary, but instead a portion
of fuel must be accelerated to super-high velocities of about 1000-1500
km/by nsec-long lasers, which is a major challenge of this scheme. Since the idea of Impact ignition was proposed, distinct milestones have been
achieved experimentally such as achievement of a velocity ~ 1000 km/s and
100 times increase of neutron yields due to the impact effect. Generation of quasimonoenergetic ions is one of the most critical issues in ion acceleration physics. Coulomb explosion is regarded as a method to produce high energetic ions by applying ultrashort ultraintense laser. Recently it has been found that by controlling the composition of clusters of diameters of about 100 nm made of two or multi-species ions can generate quasimonoenergetic ions of high quality and high conversion efficiency.