Waves for alpha channeling in mirror machines

Abstract

Alpha-channeling can, in principle, be implemented in mirror machines via exciting weaklydamped modes in the ion cyclotron frequency range with perpendicular wavelengths smaller than the alpha particle gyroradius. Assuming quasi-longitudinal or quasi-transverse wave propagation, we search systematically for suitable modes in mirror plasmas. Considering two device designs, a proof-of-principle facility and a fusion rector prototype, we in fact identify candidate modes suitable for alpha-channeling.

Applying alpha-channeling to mirror machines

“…or across (Fig. 8) the background magnetic field was proposed [34,37]. Applying this method to several practical device designs including the fusion reactor prototype [38] and the Large Plasma Device [39], several contained weakly-damped modes with parameters close to those required for efficient α channeling were found.…”

“…The identified modes are therefore trapped in a mirror machine, typically near a local minimum of B 0 and extend to a region over which B 0 changes by several percent. Should a device allow for multiple regions like that, the arrangement of multiple modes interacting with α particles within a single machine would be possible [34].…”

Alpha channeling in rotating plasma with stationary waves

“…17 The alpha channeling concept was recently extended to mirror machines. [18][19][20] In this case, the loss cone produces a convenient phase space boundary through which alpha particles can be removed. Many of the benefits of alpha channeling in tokamaks, such as increased fusion reactivity, also apply to mirrors.…”

Channeling of Fusion Alpha-Particle Power Using Minority Ion Catalysis

“…However, finding appropriate modes that would be able to interact vigorously enough with both α particles and fuel ions in a practical device can be challenging [14][15][16][17]. (For example, in mirror machines, no such weakly-damped modes have been identified yet that would allow transferring most of the energy [18].) Thus, expanding the parameter range within which the α-channeling can be practiced would be highly advantageous.…”

“…With the minority catalyst, the extracting waves no longer have to interact with α particles and fuel ions simultaneously. To illustrate how this concept can broaden considerably the parameter space of useful waves, we focus on α-channeling in mirror geometry [24], where roughly suitable waves have already been identified [18].…”