Theory and Experiment in Laser Driven Fusion
The production of fusion energy from a pellet of thermonuclear fuel can be achieved on a level useful for power production only if the pellet is highly compressed with efficient energy transfer from the external energy source into the pellet. The simple model of a uniformly compressed DT sphere can be used to determine the fusion energy production. Figure (1) gives the ratio of fusion energy output to initial thermal energy for a uniform initial temperature of 5 kev. The energy multiplication, for an initial thermal energy of one kilojoule, is 5 at a density of 300 gm/cm3, 16 at 600, 40 at 1000, and 80 at 2000. For high energy input on high compression, the energy multiplication levels off at about 200 corresponding to about 35% burnup of the DT. The energy multiplication can be increased if the fuel is only centrally heated to the ignition point of 5 kev, with the rest of the fuel ignited by an expanding supersonic burning front propagating outward from the fuel center. Figure (2) shows a typical example of the propagation of a supersonic burning front. Figure (3) shows the energy multiplication with the fuel center heated to 5 kev over a few micron radius and the rest of the fuel at 500 ev. With an initial thermal energy of one kilojoule, the energy multiplication is 130 at ρ = 600 gm/cm3, 400 at ρ=1000 gm/cm3, and 700 at ρ= 2000 gm/cm3. The energy multiplication reaches a maximum of about 1200 for initial thermal energy of 5–10 kilojoules, independent of initial density, corresponding to about 35% fuel burnup. The effect of the centrally-initiated burning wave increases the energy multiplication by about a factor of ten over the uniformly heated case.
KeywordsLaser Energy Stimulate Brillouin Scattering Neutron Production Fusion Energy Target Reflectivity
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