Electron cyclotron emission as diagnostic tool in spheromak

The potential of electron cyclotron emission (ECE) diagnostic to determine plasma parameters in spheromak experiments and spheromak reactor is examined in detail. When a linearly polarized electromagnetic wave propagates through a sheared magnetic field in dense plasma, it undergoes rotation. The amount of rotation depends on plasma parameters, magnetic field amplitude and its orientation as well as on spatial variation. We have calculated the value of the rotation angle for different anisotropy conditions. It is observed that the amount of the rotation angle is negligible for a weak anisotropy. That means the wave is propagated as if in vacuum and local information carried by the wave is preserved. We show that, by proper choice of harmonics frequency of ECE radiation, a weak anisotropy condition can be satisfied. Hence measurement of ECE radiation for those range of frequencies (for which the weak anisotropy condition is satisfied), plasma parameters and magnetic field orientation can be obtained easily. As an example, the use of this diagnostic method in existing sustained spheromak physics experiment is described. We also mention that this diagnostic can measure electron temperature with about 10 cm or less spatial resolution in a 'two-component type spheromak reactor' having electron temperature ≤7 keV. The measurement aspects of ECE for a spheromak are discussed.