Published online by Cambridge University Press: 09 March 2009
It has been recently suggested (Hora & Miley 1984) that in the cannonball scheme of laser compression the pellet may be considered to be compressed by the ‘brute force’ of the radiation pressure. For such a radiation-driven compression, this paper applies an energy balance method to give an equation fixing the radius compression ratio κ which is a key parameter for such intense compressions. A shock model is used to yield specific results. For a square-pulse driving power compressing a spherical pellet with a specific heat ratio of 5/3, a density compression ratio Γ of 27 is computed. Double (stepped) pulsing with linearly rising power enhances Γ to 1750. The value of Γ is not dependent on the absolute magnitude of the piston power, as long as this is large enough. Further enhancement of compression by multiple (stepped) pulsing becomes obvious. The enhanced compression increases the energy gain factor G for a 100 μm DT pellet driven by radiation power of 1016 W from 6 for a square pulse power with 0·5 MJ absorbed energy to 90 for a double (stepped) linearly rising pulse with absorbed energy of 0·4 MJ assuming perfect coupling efficiency.