ABSTRACT
In previous chapters, plasma was regarded as a set of point electrons and ions, moving in the electromagnetic field. However, the actual situation is far away from such a simple scheme. This is explained by the presence in heavy particles, in addition to three1 external (special) degrees of freedom, of an even larger number of internal degrees of freedom, associated with the electron shells (the only exception is the hydrogen ions) and nuclei. The nuclei will be discussed in section 10.56, and here we consider only the electronic shells and discuss indirectly the oscillations of the nuclei in the molecules. The ‘untangling’ of the internal degrees of freedom (transformation of particles2), i.e. as a result of the increase of the energy which the particles can have in the plasma. At the same time, in classic gas dynamics (kinetics) the particles remain unchanged because the energy of the particles is on the level 0.1 eV ~ 1000K. The electron energy required for the single ionisation of the neutral atoms (ions) is ~5-15 eV. A slightly larger amount of energy is required for the formation of multi-charged ions (Fig. 10.6.1)
Evidently, a mixture of neutral particles, ions of different charge Z and electrons forms in the ionisation process. The identical situation is also recorded in the vicinity of energy-absorbing walls of hightemperature thermonuclear reactors, for example, tokamaks. This takes place taking into account that the energy in the centre of these systems reaches 10 keV ≈ 108K, resulting in the start of the reactions of 1If the particles had no spherical symmetry, the number of degrees of freedom can be 5 or 6 2The ‘transformation’ of the heavy particles refers to the processes in which their internal degrees of freedom take part.
