Favorable modifications of Scrape-Off Layer (SOL) heat flux width through pulsed fuelling in ADITYA-U Tokamak

TL;DR

This study demonstrates that pulsed fuelling in the ADITYA-U Tokamak effectively broadens the SOL heat flux width, reducing heat flux and improving confinement, with validation through analytical models and simulations.

Contribution

It introduces a novel approach showing pulsed fuelling enhances SOL width and heat flux mitigation, supported by experimental, analytical, and simulation evidence.

Findings

Pulsed fuelling reduces heat flux near LCFS.

Analytical models indicate plasma diffusion influences SOL width.

Simulations show increased cross-field diffusion and inward pinch are needed.

Abstract

Enhancement of the scrape-off layer (SOL) heat flux width has been observed in the ADITYA-U Tokamak following the injection of short fuel gas pulses. A notable reduction in parallel heat flux near the last closed flux surface (LCFS) is observed after each pulse. Comparative analysis indicates that pulsed fuelling is more effective in mitigating heat flux with improved core confinement than continuous gas feeding via real-time density control. Analytical and simulation works are also carried out for validation of experimental results. The analytical model shows that SOL width modification cannot be attributed solely to the decrease of temperature due to gas pulse injection; cross-field plasma diffusion also needs to increase. Simulations with the UEDGE code suggest that an increase in both the cross-field diffusion coefficient and inward pinch velocity is necessary to replicate the experimentally observed broadening of the heat flux SOL width. These findings provide insights into efficient SOL heat flux control strategies for future fusion devices.