Maxwellian energy distribution

Figure 5.6 The left panel shows storage ring results [100] in the form of rate coefficients (shaded area) for Si3+ recombining into Si2+. The thick line is the calculated cross section [100] folded with the electron beam temperature. The energies of the resonant states (doubly excited states) in Si2+ are shown in the form of a level scheme. It is obvious that the rate coefficients map out the energy level scheme. The right panel shows the rate coefficients as a function of temperature. The upper black line shows the storage ring results folded with a Maxwellian energy distribution, see [99], while the lower grey curve shows a theoretical prediction [107].

Fig. 34. Comparison of the experimental values of the degree of dissociation, zj, with the ones calculated according to Eq. (15) as a function of residence time with the following notation dotted and dashed lines refer to maxwellian and non maxwellian energy distribution functions, respectively, a and b, to the inclusion or exclusion respectively, of A singlets in the calculations...

Plasma temperature. Generally, the concept of temperature is valid only for Maxwellian energy distributions, which cover most of plasmas but not all. In spite of this, quite often the plasma temperature is used also for plasmas of ion sources which are not in equilibrium. The ion temperatures (of z-times ionized ions) and electron temperature 7 are not necessarily equal and in the presence of magnetic field the temperatures parallel and perpendicular to the field may be different, especially for the electrons. It is usual to express the plasma temperature in electron volts (eV) using the relationship E= kT, where 1 eV corresponds to 11,600 K. Typical plasma electron and ion temperatures are several tens of electron volts. In some plasmas (e.g., ECR, see in Sect. 50.1.5.1), however, the T electron temperature can be several keVor higher. 

As for the second parameters, the electric field strength Emax, we have found more sensible to employ the electron temperature instead. In fact it was simpler to express the electron rate constants, calculated from their cross-sections and evaluated assuming a Maxwellian energy distribution function for electrons, described by a single parameter, their temperature Te. 

The dimensionless parameter which characterizes the speed distribution is the ratio of the molecular kinetic energy to kT. Thus we may determine a Maxwellian energy distribution by defining c = mc jl from which de = me dc and (1.24) becomes... 

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