Ignition and Burn Dynamics of DT Fuels in Impact Fast Ignition

On the basis of 2D hydro-base simulations, where a super-high velocity spherical DT impactor collides against a spherically-compressed stationary DT main fuel, the ignition and burn dynamics in the impact fast ignition (IFI) scheme has been investigated. It is found that the energy conversion from the impactor kinetic energy to its internal energy at the collision is not so high (20 ~ 40 %) since the main fuel is not so hard to completely stop the impactor, which makes ignition requirements harder than that expected at the previous analytical estimation [M. Murakami et al., Nucl. Fusion 46, 99 (2006)]. And the collision takes a finite time, roughly the impactor length / the impactor velocity, which should be shorter than that the main fuel confinement time. To achieve a high gain in the IFI scheme, the impactor driver energy should be much smaller than that for main fuel implosion, which requires a high compression ( ≥ 100 g/cm) and a super-high velocity acceleration (2000 ~ 2500 km/sec) for a small mass impactor (less than 10 μg) before colliding with a main fuel.