Alpha-Channeling Effects in Mirror-like Plasma

Abstract

Summary form only given. The alpha-channeling effect [Fisch, N.J., 2006] in tokamaks exploits the higher population of high-energy alpha particles in the tokamak interior compared to that of low-energy alpha particles at the periphery. Because of the population inversion, it is possible to inject radio frequency waves that diffuse resonant particles along diffusion paths connecting these regions, so that hot alpha particles diffuse to the periphery and cool at the same time. However, the population inversion for fuel deuterium ions is opposite to that of the alpha particles. There are no MeV fuel ions in the center, but there are many relatively cold fuel ions near the periphery. Thus, in a tokamak, the same wave that taps alpha particle energy, while rejecting the alpha particles to the periphery, also can fuel the plasma by sucking in fresh fuel ions and heating them. Similar possibilities might be expected in mirror geometry [Fisch, N.J., 2006]. Both mirrors and tokamaks are devices with a symmetry direction, so that the diffusion paths can be written similarly. Using effects similar to the alpha channeling effect in tokamaks, important improvements in open traps might be had through the use of rf fields interacting with mirror-confined ions, such that the ions diffuse in the rf fields along highly constrained orbits, losing energy as they are forced out of the trap. The channeling effect in magnetic mirror geometry might be used, like in tokamaks, to enhance the fusion power density of hot plasma for the purposes of energy production. However, the effect may have other applications as well in improving other uses of magnetically confined mirror-like plasma, such as occurs in plasma separations or plasma propulsion.