MEASUREMENT OF THE TIME DELAY BETWEEN MAGNETIC DIAGNOSTIC COILS IN A TOKAMAK USING CROSS-SPECTRAL ANALYSIS
A. A. Nasimi1, Sh. Saadat1, B. Mansouri1,2
1Islamic Azad University, Ahvaz, Iran
2Shahid Chamran University of Ahvaz, Ahvaz, Iran
Keywords: токамак, плазма, кросс-спектральный анализ, периодограмма, временная задержка, tokamak, plasma, cross-spectral analysis, periodogram, time delay
Abstract
The delay in detecting the position and shape of the plasma confined by a tokamak increases plasma instability and decreases the accuracy of plasma control in the tokamak. In this article, two techniques called periodogram and cross-spectral analysis are used to provide a quantitative approach for computing the time delay between the data obtained by two different coils from one source (plasma fluctuations) in the IR-T1 tokamak. After performing the Fourier transform of the data, the periodogram, square coherency, and phase diagram are plotted in terms of frequency in three different time intervals. In the time interval 29000 < τ < 30000 µ, where the plasma current is almost constant, the average phase shift between the frequency components of the data is obtained by using the phase spectrum analysis. The time delay between the data for the Rogowski and Mirnov coils is observed at the frequency of the highest coherency: τd = 1,831 µ.
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