Patent Number: 043280706
Section: summary

BACKGROUND OF THE INVENTION There is a growing interest in drivers others than lasers to compress and ignite small quantities of thermonuclear fuel for the release of energy by inertial confinement. The reason for this search of alternative drivers are the inherent disadvantages of laser fusion. One of these disadvantages is the comparatively long wave length of laser light and which is not well matched to the plasma frequency at the desired high target densities which shall be reached by implosive compression. Lasers furthermore suffer from low efficiency and high cost. Finally, the problem of stimulated Brillouin backscattering from the target sets an upper limit for the laser power. Other driver options presently under study include beams of charged particles ranging from electrons to heavy ions and even projectiles accelerated to hypervelocities. However, the very large requirements in beam power combined with good beam focusing is likely to make any one of these alternative concepts also rather expensive. In case the ignition is done with heavy ion beams generated by conventional particle accelerators, the length of these accelerators will be many km. The same is true for the concept of impact fusion by the magnetic acceleration of a small superconducting solenoid to hypervelocities. The original proposals for several of these alternative driver concepts, for example the pulsed acceleration of an intense beam of ions by a magnetically insulated diode, were made by the inventor a long time ago. SUMMARY OF THE INVENTION In the proposed invention the high power required to drive an ablatively driven thermonuclear target is drown from intense black body radiation trapped and compressed inside a small cavity. The work to compress and hence amplify the black body radiation can be drawn from a variety of external sources, which may include lasers, charged particle beams, hypervelocity projectiles and even focused chemical explosion waves. When these energy sources are directly used to drive an inertial confinement fusion microexplosion, the required beam power and beam power density are much larger. In the invention proposed, the initial drive energy is converted into black body radiation by a shock wave. The thusly generated black body radiation is then intermediately stored inside a small cavity before being delivered to the thermonuclear target. This intermediate energy storage into black body radiation is the reason why the intial driver power is here much smaller than in case these drivers are directly used for thermonucler ignition. The basic concept of the idea is explained in FIG. 1 showing how the invention works for a beam induced ablatively driven implosion of a small cavity. In FIG. 2 an arrangement is shown how this can be done using a hypervelocity projectile. In the first case shown in FIG. 1 the cavity is spherical and in the second case shown in FIG. 2 conical. However, other cavity geometries are also possible. In any one of these geometries the thermonuclear target is placed inside the cavity. It is also possible to have a multistage assembly of concentric spherical shells imploding on each other and whereby the black body radiation generated in the space in between these shells ablatively implodes the next inner shell.