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Author(s):
A. Ejiri, K. Shinohara and K. Kawahata
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Title:
An Algorithm to Remove Fringe Jumps and its Application to Microwave Reflectometry
Date of publication:
Apr. 1997
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Key words:
algorithm, microwave refletometry, fringe jumps, phase runaway, Poisso process, Power spectrum
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Abstract:
In some plasma discharges, the phase measured by microwave reflectometry has many fringe (2 pi rad.) jumps. A new algorithm to detect and remove fringe jumps has been developed, and applied to the data in the JIPP TII-U tokamak. Using this algorithm, quantitative properties of fringe jumps, and their effects on the analysis of phase fluctuations are Investigated. It was found that the fringe jumps occur randomly, and the distribution of the time scale (half period) of jumps has a peak around 4 ~ 6 mu s. The rms value of high frequency phase fluctuations in fringe jump periods is Iarger than that in fringe jump-free periods. Besides this high frequency fluctuation, fringe jumps themselves have much smaller power than that of fluctuations in high frequency range. In low frequency range, however, the power spectrum is dominated by the random fringe jumps.
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