Microwave reflectometry with the extraordinary mode on tokamaks: Determination of the electron density profile of Petula-B

Abstract

Articles you may be interested inDesign of an X-mode fast-scanning reflectometry for edge density profile measurement on HT-7 tokamak Rev. Sci. Instrum. 74, 1522 (2003; 10.1063/1.1527253 Ultrashort pulse reflectometry for electron density profile measurements Rev. Sci. Instrum. 70, 1038 (1999); 10.1063/1.1149530Broadband reflectometry for the density profile and fluctuation measurements in the JT60 tokamak (abstract) Rev. Sci.The use of an ordinary mode refiectometer has already proved to be a good means for determining the density profile of a plasma, but the fact that this mode reflects where its frequency equals the local plasma frequency restricts its use to the region of the density gradient. The extraordinary mode refiectometry investigated here permits the observation of the scrape-off layer as well as the near-axis region and in certain conditions also the high magnetic field side of the density profile. It is also shown that this mode requires a range of frequency sweep for measuring a given density profile smaller than the ordinary mode. On the Petula-B tokamak, the density profile has been measured in 200 ps, its evolution when applying the lower hybrid current drive could be also followed. Since the measurement is particularly sensitive near the reflection point of the wave, it could be used to determine precisely the position of magnetic islands and the fluctuation amplitudes. In addition, the access and place occupied in the vacuum chamber being very small, this diagnostic should be compatible with reactor conditions. 539

Turbulence correlation properties measured with ultrafast sweeping reflectometry on Tore Supra

“…In order to isolate the signal reflected by the plasma a sliding filtering technique [11] is used, with a sliding bandwidth of 100 MHz around the beat frequency evolution. The electron density profile is reconstructed for each frequency sweep according to the Bottollier-Curtet recursive algorithm [13,14]. The radial dependence of the cut-off frequencies is given from the mean density profile which is obtained by averaging over the N sweeps acquired during a single burst.…”

Разработка Комплекса Двухполяризационной Рефлектометрии Торсатрона Ураган-2м

“…Следует отметить, однако, что потенциал рефлектометрии для традиционного изме-рения профилей плотности далеко не исчерпан. Так, еще в работе [10] обсуждалась возможность применения рефлектометрии с использованием необыкновенной (X-) волны для измерения профиля плотности плазмы в токамаках. В этой работе полностью пренебрегалось влиянием полоидального магнитного поля токамака на набег фазы необыкновенной волны.…”

“…Как следует из (2), для определения профиля плот-ности необходимо знать d (ω)/dω. В действующих комплексах рефлектометрии для измерения d (ω)/dω используется быстрое свипирование частоты генерато-ра [6,10]. При известных dω/dt и сигнале с фазового…”

Density profile measurements with X-mode lower cut-off reflectometry in ASDEX Upgrade

“…3 for frequencies below the first lower cut-off probing frequency f 1 . The profile inversion is carried out using the Bottollier-Curtet algorithm 6 . Fig.…”