A new simpler way to obtain high fusion power gain in tandem mirrors

Abstract

From the earliest days of fusion research, Richard F. Post and other advocates of magnetic mirror confinement recognized that mirrors favor high ion temperatures where nuclear reaction rates σv begin to peak for all fusion fuels. In this paper we review why high ion temperatures are favored, using Post's axisymmetric Kinetically Stabilized Tandem Mirror as the example; and we offer a new idea that appears to greatly improve reactor prospects at high ion temperatures. The idea is, first, to take advantage of recent advances in superconducting magnet technology to minimize the size and cost of End Plugs; and secondly, to utilize parallel advances in gyrotrons that would enable intense electron cyclotron heating (ECH) in these high field End Plugs. The yin-yang magnets and thermal barriers that complicated earlier tandem mirror designs are not required. We find that, concerning end losses, intense ECH in symmetric End Plugs could increase the fusion power gain Q, for both DT and Catalyzed DD fuel cycles, to levels competitive with steady-state tokamaks burning DT fuel. Radial losses remain an issue that will ultimately determine reactor viability.

Prospects for a high-field, compact break-even axisymmetric mirror (BEAM) and applications

“…A preliminary neutronics analysis for a 10 MW neutron output (achievable with additional heating power even if Q < 1) has illustrated that such a FVNS could have both materials testing and blanket testing missions. We note that this same device (even at modest Q) would be a central component of the development path needed for the tandem mirror and demonstrate the necessary conditions required of an end plug Fowler et al (2017). Furthermore, there are numerous other applications for powerful fusion neutron sources such as recycling spent nuclear waste (Moir et al 2012;Ruegsegger et al 2023) that are beyond the scope of this paper.…”

“…An obvious advance would be to test mirror performance with TFTR/DIII-D/Asdex-U class neutral beams where the beams primarily fuel (rather than charge exchange) and the resulting beam distribution functions collisionally relax to classical mirror predictions. Nearly classical confinement in BEAM would also largely retire the risk in performance needed to embark on a tandem mirror for large-scale power production (Fowler, Moir & Simonen 2017).…”

“…2010; Fowler et al. 2017) and affect the electron temperature. The ETG might be relatively unaffected by the sheared ion flow and FLR effects because the relative lengths for electron-scale turbulence are a square root mass ratio smaller.…”

Guiding centre motion for particles in a ponderomotive magnetostatic end plug

“…1980; Volosov & Pekker 1981; Hassam 1997; Fetterman & Fisch 2008, 2010 a , b ; Teodorescu et al. 2010; Fowler, Moir & Simonen 2017; White, Hassam & Brizard 2018; Miller et al. 2023).…”

Dinámica y control de un reactor de fusión nuclear. El caso del proyecto ITER

“…Bobina espejo Figura 1.4: Esquema del funcionamiento básico de una conguración de espejo magnético, imagen obtenida de (Fowler et al, 2017).…”