A new approach for diagnostics of dense magnetoactive plasmas using the effect of parametrically induced transparency

We study theoretically the effect of parametrically induced transparency. The main idea of this effect is transport of the upper-hybrid radiation of overdense toroidal plasmas in vacuum through the opaque region by parametric shift of the radiation frequency. We propose that the microwave radiation employed for electron-cyclotron heating at the second cyclotron harmonic in tokamaks is used as the drive wave. Calculations performed for the TEXTOR tokamak demonstrate that this effect is promising for diagnostics of dense plasmas in toroidal devices if a gyrotron with an ouput power of several hundred kilowatts is used.