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A zero-dimensional model that describes the evolution of plasma and gas parameters during the afterglow phase of cyclic operation of an inertial fusion energy chamber is developed. The afterglow phase determines the conditions for next fuel-target injection and therefore its thorough analysis is very important for conceptual design of inertial fusion power plants. The model incorporates important effects of intrinsic impurity ion radiation on plasma cooling as well as of chamber opacity with respect to resonance radiation on plasma recombination in the working chamber. The decay times for the plasma and gas energy and, in particular, their dependence on initially stored energy, chamber size, and background gas concentration are analyzed. The heat power load onto the cryogenic fuel target due to residual plasma, gas, and radiation field is calculated. It is found that the higher the background gas density, the longer is the time into the afterglow phase necessary to reduce the heat flux on the target to an acceptable level.

As is true for current-day commercial power plants, a reliable and economic fuel supply is essential for the viability of future Inertial Fusion Energy (IFE) [Energy From Inertial Fusion, edited by W. J. Hogan (International Atomic Energy Agency, Vienna, 1995)] power plants. While IFE power plants will utilize deuterium-tritium (DT) bred in-house as the fusion fuel, the “target” is the vehicle by which the fuel is delivered to the reaction chamber. Thus the cost of the target becomes a critical issue in regard to fuel cost. Typically six targets per second, or about 500 000∕day are required for a nominal 1000MW(e) power plant. The electricity value within a typical target is about $3, allocating 10% for fuel cost gives only 30 cents per target as-delivered to the chamber center. Complicating this economic goal, the target supply has many significant technical challenges—fabricating the precision fuel-containing capsule, filling it with DT, cooling it to cryogenic temperatures, layering the DT into a uniform layer, characterizing the finished product, accelerating it to high velocity for injection into the chamber, and tracking the target to steer the driver beams to meet it with micron-precision at the chamber center.