Optimum Interferometry in Plasma Devices

The optimum interferometers for measurement of plasma density distribution constructed by the classical scheme are examined. It is shown that the maximum precision of such interferometer depends only on a level of its vibrations both the geometrical sizes of plasma and interferometer. For different magnitudes of plasma densities this precision is implemented in different wavelengths of sounding radiation. The parameters of the universal ultra-low-noise ir/submillimeter laser are given. It is a suitable source for various optimum interferometers in closed and open traps.