Sufficiently small, the particle is trapped in a local magnetic mirror and never gets to the inside of the torus. It is reflected back when the field magnitude B> mV2/2μ where μ is thE(constant) magnetic moment and V is the magnitude of the particle velocity. This particle then is trapped, exactly as a particle in a magnetic mirror. Of course, for the particle to be trapped, the plasma must be sufficiently collisionless that a trapped particle can complete its orbit before being collisionally scattered out of its trapped state. The collision frequency necessary is called the effective collision frequency (Vef) and is specified in Chap. 4. If the bounce frequency of the particle in the local mirror is ωb, (specified in Chap. 8), then the particle can make a complete trapped oscillation of ωb > vef If so, then the tokamak is said to be in the banana regime because, when cross-field drifts are accounted for, the trapped orbit has the general shape of a banana.
展开▼
