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Abstract

In this paper a broadband heterodyne reflectometer operating in the frequency range 75-110 GHz in extraordinary mode polarization is used at the W7-AS stellarator for both fast density profile determination and density fluctuation studies. This probing signal is amplitude modulated at a frequency 133 MHz using the envelope phase for profile evaluation and the carrier phase to determine the fluctuation information simultaneously. Separate Gaussian beam optics for final signal launch and detection permits a beam waist of about 2 cm at the reflecting layer in the plasma. Amplitude modulated detection is accomplished in the intermediate frequency part by synchronous detection after recovery of the carrier by narrow-band filtering. Voltage controlled solid state oscillators followed by active frequency multiplication allow to scan the full frequency band within less than 1 ms. For typical W7-AS operation the accessible density range 1E19 to 6E19 m{-3} for on axis magnetic field of 2.5 T and 4.5E19 to 1E20 m{-3} for 1.25 T, respectively. The probed radial positions range between 0.2<r/a<1.1 depending on plasma conditions (a approximately 17 cm).

Additional information

Authors: HIRSCH M, Max-Planck-Institut für Plasmaphysik, Garching bei München (DE);HARTFUSS H J, Max-Planck-Institut für Plasmaphysik, Garching bei München (DE);GEIST T, Max-Planck-Institut für Plasmaphysik, Garching bei München (DE);DE LA LUNA E, Max-Planck-Institut für Plasmaphysik, Garching bei München (DE)
Bibliographic Reference: Article : Reviews of Scientific Instrumentation, Vol. 67 (1996) No. 5, pp. 1807-1813
Record Number: 199610891 / Last updated on: 1996-09-16
Category: PUBLICATION
Original language: en
Available languages: en