Cyclotron Radiation from a Hot Plasma

Abstract

In their Geneva paper, Trubnikov and Kudryavtsev calculated the cyclotron radiation from a hot plasma. In doing this, the assumption was made that the individual particles radiated as though they were in a vacuum. We have investigated this approximation by calculating the absorption length directly from the Boltzmann equation, and we find that indeed this assumption is correct whenever (ωp/ωe)2 ≪ m2, where m is the harmonic number of the radiation in question, ωp is the plasma frequency, and ωe is the cyclotron frequency. For a contained plasma, the left hand side of this inequality is of the order of magnitude of one, and thus the inequality is well satisfied for the dominant radiation from a plasma at high temperature. The angular independence of the absorption coefficient has been calculated, and this together with a more careful examination of the mechanism of thermonuclear energy transfer to the electrons, leads to a modification of the results presented by Trubnikov and Kudryavtsev at Geneva. In addition, it is shown that by the use of reflectors the critical size can be reduced by two orders of magnitude.