Effect of MHD on Gas Puff Induced Cold Pulse Propagation in ADITYA-U Tokamak

Cold pulse propagation has been recently studied and characterized with short gas puff of fuel H₂ gas in ADITYA-U tokamak, each gas puff injecting ~ 10¹⁷-10¹⁸ molecules. The edge temperature shows a sharp decrease while the core temperature increases promptly, faster than energy confinement time. The occurrence of the cold pulse is preceded by an even faster rise in the chord averaged density. The increase in the density is attributed to an increase in the inward pinch velocity and a decrease in the ion obit loss in ADITYA-U. In this work, the effect of MHD modes on the density rise is studied. A parametric study is undertaken with the variation of MHD mode amplitude, chord averaged density, amount of injected neutrals and toroidal magnetic field. The density rise is observed to occur much faster in the presence of significant MHD activity. The study has relevance to the overall fueling efficiency in presence of MHD activity.