Confinement of Charged Particles by Multiple-Mirror Systems

The magnetic mirror approach to fusion

“…The linking together of mirror cells to enhance mirror confinement times has been frequently suggested. One of the early ideas is that of multiple mirrors [12]. The basic concept is simple to describe: Consider a linear system consisting of many identical symmetric mirror cells linked together.…”

Rate equations model for multiple magnetic mirrors in various thermodynamic scenarios

“…Therefore the most important parameter is the system collisionality, l/λ , where l is the mirror cell length and λ = v th /ν s is the MFP. [9][10][11][12][13][14][15][16][17][18] Since v th ∝ √ T and ν s ∝ n/T 3/2 (see section II B), the MFP scales as λ ∝ T 2 /n. 30 If the system is isothermal, i.e., the temperature is the same in all cells, the MFP increases as the plasma expands, and the density drops towards the outer MM cells.…”

“…While the flute instability can be controlled with passive, 1,2 RF, 3,4 and active 5,6 methods, the loss cone flux limits the achievable fusion gain to a non-practical level in simple linear machines. In the past, several magnetic configurations have been suggested in order to reduce the axial outward flux including, tandem plugs with thermal barriers, 7,8 multi-mirrors (MM) [9][10][11][12][13][14][15][16][17][18] moving multi-mirrors, 19,20 and Helical mirror with plasma rotation. 21,22 Here, we will focus on the MM configuration.…”

Open-Ended Magnetic Confinement Systems for Fusion

“…One of these ways, one that had been suggested and studied many years earlier [11,12], was to employ many mirror cells in series, arranging matters so that particles escaping from the innermost cell would be successively trapped in the outer cells, thereby achieving a confinement time that increased as the square of the number of cells, in this way regaining a scaling analogous to the quadratic scaling with size of closed systems. The difficulty, at that time, with the multiple-mirror idea was that i t seemed to require such high plasma densities, and/or such long cells (to achieve collisional retrapping in each cell) as to make the entire system impractical.…”

“…As noted earlier, the axial symmetry of the mirror coils allows the possibility of reaching much higher field strengths than that that is possible with non-axi-symmetric coils. As the mirror coils can be made quite short, and since the plasma diameter in the mirror throat will be relatively small (10)(11)(12)(13)(14)(15) cm. ), it is quite conceivable that magnetic fields up to 45-50 Tesla will prove to be feasible to attain in practical systems.…”