| Popis: |
The ZETA plasma is believed to contain field-aligned irregularities in density, loosely called turbulence. Such irregularities cause scattering of a microwave beam traversing the plasma, and will also affect the emission of thermal microwave noise. To calculate the effect on the emissivity, a naive model of the turbulence is taken in which the individual turbulence elements are considered to be parallel cylinders, the density profile within the cylinders being parabolic. A ray theory treatment of the emissivity of a cylinder is combined with a statistical treatment of the radiation mean free path, and the time-averaged emissivity of the plasma is calculated in terms of element size, spacing and central density, the plasma electron temperature and the size and reflectivity of the containing vessel. It is found that the turbulence can increase or decrease the emissivity several-fold according to the values of the various parameters, and that the range of variation is sufficient to encompass the discrepancies between observed and calculated emissivities previously reported. |
