Analysis the Turbulence Modulation at the Edge of IR-T1 Tokamak through Biasing and Resonant Helical Magnetic Field by Empirical Mode Decomposition Technique

Abstract

In this study, we investigated the influence of biasing and Resonant Helical Magnetic Field (RHF) on plasma current, ion saturation (\({{I}_{{{\text{sat}}}}}\)), and the gradient of floating potential (\(\nabla {{V}_{f}}\)) using the Multi-Directional Langmuir Probe (MDLP) at the plasma edge in IR-T1 tokamak. The experiment was conducted in three scenarios: only biasing, only RHF, and biasing with RHF (biasing voltage fixed at V = 250 V on plasma edge, RHF with L = 2 and L = 3) were applied to the plasma. Biasing with RHF resulted in an increase in plasma current (19–21 kA), enhanced plasma confinement time (33–34 ms), and reduced plasma resistance. Simultaneously applying biasing and RHF led to an increase in plasma energy compared to the situation with no biasing and RHF \({{I}_{{{\text{sat}}}}}\) decreased by 25% in biasing, 5% in RHF, and 40% in biasing with RHF. \(\nabla {{V}_{f}}\) fluctuations decreased by 3, 2, and 4%, respectively. Applying biasing with RHF reduced the cross-correlation between \(\nabla {{V}_{f}}\) and \({{I}_{{{\text{sat}}}}}\), increasing their phase difference. Empirical Mode Decomposition (EMD) revealed that biasing with RHF decreased the overall average of Intrinsic Mode Functions (IMFs) amplitude for \(\nabla {{V}_{f}}\) and \({{I}_{{{\text{sat}}}}}\) compared to the absence of biasing with RHF.