Progresses of Impact Ignition

Full text: In impact ignition scheme, a portion of the fuel (the impactor) is accelerated to a super-high velocity, compressed by convergence, and collided with a precompressed main fuel. This collision generates shock waves in both the impactor and the main fuel. Since the density of the impactor is generally much lower than that of the main fuel, the pressure balance ensures that the shock-heated temperature of the impactor is significantly higher than that of the main fuel. Hence, the impactor can reach ignition temperature and thus become an igniter. Here we report major new results on recent impact ignition research: (1) A maximum velocity ∼ 1000 km/s has been achieved under the operation of NIKE KrF laser at Naval Research Laboratory (laser wavelength = 0.25 μm) in the use of a planar target made of plastic and (2) We have performed two-dimensional simulation for burn and ignition to show the feasibility of the impact ignition. It is concluded that, by increasing the impactor velocity from 700 km/s to over 1500 km/s, and the energy efficiency from 2% to 10%, we estimate the laser energy necessary to create a hot spot to ignite DT fusion fuel to be 200 - 300 kJ, which is much lower than that required for central ignition. Scaling up of the present experiments will demonstrate that full-scale impact ignition could be attained within a practical range. (author)