Page 28 - Fundamentals of Magnetic Thermonuclear Reactor Design

Facilities With Magnetic Plasma Confinement Chapter | 2 11

l More complicated magnetic mirror configurations (Fig. 2.3B).
l Configurations including three magnetic mirrors placed along one axis – the
so-called ambipolar, or tandem, mirrors (Fig. 2.3C). Their topology includes
two smaller magnetic mirrors placed close to the ends. An increased plasma
escape through the end mirrors is accompanied with the development of an
ambipolar potential that ‘plugs’ the plasma within the central trap, enhanc-
ing the confinement.
l Magnetic multimirror facilities or the so-called gas-dynamic multiple-
mirror traps.
Experimental results and theory now point to a near-term possibility of us-
ing open-ended magnetic confinement systems as a fusion neutron source.

2.2.4 Hybrid Systems
So far, several different hybrid solutions have been proposed for quasi-station-
ary magnetic plasma traps, including the tokamak-mirror and stellarator-mirror
systems. Hybrid systems employ toroidal inserts of different configuration
(Fig. 2.4), rather than magnetic mirrors for ‘closing off’ the ends of a plasma
column.

2.2.5 Pinches
Pinches are pulsed facilities that use the effect of ‘self-contracting’ discharges:
electric current travelling through the plasma generates a magnetic field that
compresses the plasma, insulates it thermally and heats it (Figs. 2.5 and 2.6).
Pinches are divided into straight and toroidal in terms of geometry and into
Z- pinches and θ-pinches in terms of the direction of the current in a device. The
pinch devices differ from quasi-stationary systems by a much greater plasma
density and correspondingly smaller size.

FIGURE 2.4 Different hybrid systems. (A) A mirror-stellarator hybrid [1], (B) the DRAGON
trap device [2].