The neutron yields observed in inertial confinement fusion experiments for higher convergence ratios are about two orders of magnitude smaller than the neutron yields predicted by one-dimensional models, the discrepancy being attributed to the development of instabilities. We consider the possibility that ignition and a moderate gain could be achieved with existing laser facilities if the laser driver energy is used to produce only the radial compression of the fuel capsule to high densities but relatively low temperatures, while the ignition of the fusion reactions in the compressed fuel capsule will be effected by a synchronized hypervelocity impact. A positively-charged incident projectile can be accelerated to velocities of 3.5 x 10^6 m/s, resulting in ignition temperatures of about 4 keV, by a conventional low-beta linac having a length of 13 km if deuterium-tritium densities of 570 g/cm^3 could be obtained by laser-driven compression.
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