A schematic view of cross-section of BETA and diagnostics. Schematic electrical connection is also shown. All the probe measurements are performed close to the plane of the limiter and in the horizontal plane z = 0. The radial position indicated by r in the rest of the plots, is with respect to the minor axis. The toroidal field coils and filament heating circuit are not shown here.
Mean radial profiles of (a) ion saturation current, (b) electron temperature, and (c) plasma density. Comparative profiles of all the parameters for three gases are shown. For the estimation of density, corresponding values are used. The error bars obtained from multiple measurements at each location are found to be small.
Mean radial profiles of (a) floating potential and (b) plasma potential. Comparative profiles of both the parameters for three gases are shown. The entire profile may be shifted further negative by , accounting for the half the voltage drop across the emissive probe filament.
Relative fluctuation profiles of (a) ion saturation current and (b) floating potential are shown for all three gases. With fluctuations in being small and . In (c), the ratio of potential to density relative fluctuations is shown.
The fluctuation driven poloidal flux is shown for three gases. Due to short wavelength nature of the fluctuations, estimates close to the minor axis are not reliable and hence not shown here.
The net poloidal flow velocity profiles from measured upstream and downstream to the flow (a) in units of local and (b) in absolute velocity units. The large values of in (b) in the region , can be due to large values of .
Comparative plot of poloidal flow for all three gases; (a) argon, (b)krypton, and (c) xenon. In each case, the net flow is compared with mean electric field driven flow and fluctuating electric field driven flow.
Typical density and potential auto power spectra on HFS and LFS for all the three gases. Frequency is indicated by f and power is indicated by and for density and potential, respectively. (a) and (c) are power spectra of and , respectively, at −5 cm. Similarly, (b) and (d) are at +5 cm.
Profiles of cross-phase for (a) fundamental frequency and (b) second harmonic; coherence for (c) fundamental frequency and (d) second harmonic of density and potential fluctuations for all gases. For Ar, fundamental frequency is the dominant mode over the entire radial domain. On LFS for Kr and Xe, second harmonic becomes comparable or dominant than the fundamental frequency. Change in the sign when indicates either a small lead or lag in the propagation of potential to density fluctuations.
A tabular summary of the dominant fluctuations and respective harmonics, shown in brackets, on HFS and LFS for all the gases. The “mixed” case indicates that flute (II: R-T) type and non-flute (I: resistive R-T) like modes have comparable powers, i.e., . I and II indicate first and second harmonic, respectively.
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