Submillimeter quasi-optical homodyne multipass interferometer for low electron density plasma diagnostics

A new method is proposed for increasing the sensitivity of submillimeter interferometry used in plasma diagnostics. The quasi-optical homodyne backward wave tube interferometer is developed and the sensitivity is increased by more than one order of magnitude. The registered phase shift is enhanced with a multipass interferometric unit. The resulting phase shift is calculated explicitely. The effective number of the multipass unit is about 10 at the wavelength of 0.5 mm. (D.Gy.)