Single-particle radiation near electron cyclotron harmonics

In this paper the single-particle component of the radiation spectrum of a positive column in a magnetic field near the electron cyclotron harmonics is studied both experimentally and theoretically. The microwaves from the plasma have been collected by means of different cavities resonating on various modes. Thus it has been possible to show that the single-particle radiation originates mainly from the sheath. In the theoretical calculation the intensities were predicted on the basis of the Bickerton and von Engel model of the sheath and under the assumption that over an electron orbit the electric field could be approximated by constant plus linear plus quadratic terms. One finds a good quantitative agreement between the experimental and theoretical results in so far as the intensities of the harmonics are concerned, while the average frequencies of the lines turn out to be slightly different.