What are the fastest routes to fusion energy?

Abstract

In recent years, the effort to develop practical fusion energy has rapidly evolved from a focus on only tokamak and laser inertial devices to include a wide array of approaches. We survey this increasingly diverse set of routes to fusion to assess what approaches are likely to lead to practical fusion with the least outlay of resources and thus are potentially the fastest routes. While a conclusive answer can only be determined once some approach actually succeeds in producing a practical fusion-energy generator, and the speed of advance depends on the allocation of resources, it is possible to arrive at tentative conclusions now. We find that basic, long-standing obstacles make the path to practical fusion more difficult, and more resource-intensive, for all approaches using deuterium fuels (DT, DHe3) as well as for approaches with low-density plasma. The approaches that combine hydrogen-boron (pB11) fuel with high-density plasma have an easier, less resource-intensive path. At present, only a few private companies have joined the government projects in actually publishing fusion yield results. However, so far these results reflect the basic advantages of high-plasma-density approaches.