Amplitude modulated heterodyne reflectometer for density profile and density fluctuation profile measurements at W7-AS

Journal Article · Wed May 01 04:00:00 EDT 1996 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.1146978· OSTI ID:285375

Hirsch, M; Hartfuss, H; Geist, T; de la Luna, E ^[1]

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1. Max-Planck-Institut fuer Plasmaphysik, EURATOM-Ass., 85748 Garching (Germany)

A broadband heterodyne reflectometer operating in the frequency range 75{endash}110 GHz in extraordinary mode polarization is used at the W7-AS stellarator for both fast density profile determination and density fluctuation studies. The 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 is 1{times}10{sup 19} to 6{times}10{sup 19} m{sup {minus}3} for on axis magnetic field of 2.5 T and 4.5{times}10{sup 19} to 10{times}10{sup 19} m{sup {minus}3} for 1.25 T, respectively. The probed radial positions range between 0.2{lt}{ital r}/{ital a}{lt}1.1 depending on plasma conditions ({ital a}{approx_equal}17 cm). {copyright} {ital 1996 American Institute of Physics.}

• OSTI ID: 285375
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 5 Vol. 67; ISSN 0034-6748; ISSN RSINAK
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ELECTRON DENSITY
FLUCTUATIONS
GHZ RANGE
MICROWAVE EQUIPMENT
PLASMA DIAGNOSTICS
REFLECTIVITY
STELLARATORS