Events
Alpha Channeling in Tokamaks and Mirrors
00:00 26-12-2006
The alpha-channeling effect 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 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 machines. 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.
