fabrication and economic issues quantitatively, but the material and fabrication costs of the expended portions of the system will certainly be a factor in Z-pinch power plant economics. Because of the limited ICF target physics database, incomplete validation of the design tools and methodologies, and related lack of an integrated, high-yield target design, a consistent set of requirements and solutions for the pulsed-power driver, RTL, and ICF target cannot be articulated at this time. Therefore, the overall credibility of the energy delivery system and the ICF target performance cannot be quantitatively evaluated.

CONCLUSION 4-13: Sandia National Laboratories is leading a research effort on a Z-pinch scheme that has the potential to produce high gain with good energy efficiency, but concepts for an energy delivery system based on this driver are too immature to be evaluated at this time.

The Z-pinch scheme is completely different from the NIF and HIF approaches and therefore serves as risk mitigation for the ICF and IFE programs. It is not yet clear that the work at SNL will ultimately result in the high gain predicted by computer simulations, but initial results are promising and it is the panel’s opinion that significant progress in the physics may be made in a year’s time. The pulsed-power approach is unique in that its goal is to deliver a large amount of energy (~10 MJ) to targets with good efficiency (.10 percent) and to generate large fusion yields at low repetition rates.

CONCLUSION 4-14: The target manufacturing and delivery processes that are proposed for direct-drive heavy-ion and pulsed-power fusion energy are less developed conceptually and technically than the targets for laser-based fusion energy. This is primarily because the priority has been to emphasize the implosion physics and driver issues (pulsed-power and linear accelerators). The pulsed-power target appears to be straightforward to manufacture, difficult to field, and challenging to reprocess after the thermonuclear event. In contrast, the heavy-ion targets possess many synergies with the laser-based target, but because a final target design is far from being defined, potential manufacturing complexities cannot be accurately assessed. The target delivery method for pulsed-power fusion is more conceptual than for laser- or heavy-ion-based fusion and presents very different problems—for example, a very much larger mass (~1,000 times larger), a slower replacement frequency (~100 times slower), and potentially a greater radioactive waste disposal problem.

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