RADIATION TEMPERATURE OF NONEQUILIBRIUM PLASMAS

In fusion devices measurements of the radiation temperature T(r) (omega,k) near the electron cyclotron frequency omega(c) and the second harmonic 2-omega(c) in directions nearly perpendicular to the confining magnetic field B (i.e., k almost-equal-to k perpendicular-to) serve to map out the electron temperature profiles T(e) (r,t). For optically thick plasmas at thermodynamic equilibrium T(r) = T(e). However, there is increasing experimental evidence for the presence of nonequilibrium electron distributions (such as a drifting Maxwellian with appreciable values of the streaming parameter zeta = upsilon(d)/upsilon(t), a bi-Maxwellian, an anisotropic Maxwellian with T perpendicular-to not-equal T parallel-to, etc.) in tokamak plasmas, especially in the presence of radio-frequency heating. Examined here (both nonrelativistically and relativistically), is the dependence of T(r) on zeta, T perpendicular-to/T parallel-to, T(h)/T(b), n(h)/n(b), etc., where n(b), n(h), T(b), and T(h) are the densities and temperatures, respectively, of the bulk and the hot components of the bi-Maxwellian plasma. The bi-Maxwellian results predict that the ratio T(r)/T(e) is a very sensitive function of the ratios n(h)/n(b) and T(h)/T(b). Further, these relativistic and nonrelativistic results satisfy the well-known "limit c --> infinity correspondence principle," showing that the intensity of the emission and absorption line is independent of the line broadening mechanism. An alternative derivation of the "Trubnikov O-mode factor" is given in the Appendix. A number of side issues relevant to the existing disagreement between the Trubnikov results and those of some authors (in the published literature) for the O-mode processes are raised, and the plausible physical reasons for this disagreement are also pointed out in the Appendix and footnotes.