The energy gain of laser-compressed pellets is calculated. The model used is that of a uniformly compressed pellet of DT ignited by a small, hot central “spark”. Curves are presented showing the relation between energy gain and inertial confinement. Simple formulas are given that describe the least laser-pulse energy required to achieve a desired energy gain.

The theory of homogeneous isentropic compression is extended to the case of hollow shells, and exact results for the growth of Rayleigh-Taylor instability during such compressions are obtained. Earlier results on the optical power PL required to achieve a given measure of inertial confinement ρR of a laser-driven isentropically-compressed DT pellet are extended to include the case of hollow shells. – It is found that a five-fold reduction in peak power should be attainable by imploding a hollow shell having an unablated-wall thickness equal to 10% of its radius, instead of a solid pellet. Further reductions in wall-thickness and peak optical power appear to be strongly limited by Rayleigh-Taylor instability.

The hydrodynamic theory and properties of spherical homogeneous isentropic compression are discussed. Computer results are described showing that a close approximation to compressions of this type may be accomplished by light-induced pellet ablation if the light absorbed by the pellet is properly programmed with time, and is spatially uniform over the pellet surface. Pellet compressions in excess of ten thousand-fold are computed.

It is shown that a relatively weak initial shock introduced into an otherwise isentropic hollowshell implosion can cause central fuel ignition, the bulk of the fuel undergoing little increase in entropy. The imploded-state fuel configuration is analysed at the threshold of ignition, and it is found that electron heat conduction is the predominant cooling mechanism opposing fuel ignition. Approximate temperature-dependent ρR requirements are presented for the conduction-limited ignition of thin DT shells, and for the equality of electron heat conduction and α-particle transport in thermonuclear burn propagation.

The optical power P L required to achieve a given measure of inertial confinement pR of a laser-compressed DT pellet is found to be approximately proportional to (pR) 2 . This result is based on a model of self-regulating pellet ablation by hot electrons of the pellet corona that is relatively insensitive to the details of the pellet ablation process. To achieve values of pR believed necessary in the application of laser fusion to commercial power production, 3 x 10 15 W of optical power is found to be required, implying a total laser output aperture of 30 m 2 . (The same power requirement would appear to apply to pellet compression by charged-particle beams.) An estimate of the required laser-pulse energy W^, assuming corona-core decoupling to be the controlling limitation, is also given. In the application to commercial power production the required pulse energy is found to range from 70 kj at 0.265 pm to 3 Ml at 10. 6 fim.