Pellet fuelling of plasmas with ELM mitigation by resonant magnetic perturbations in MAST

TL;DR

This study investigates how shallow pellet fuelling affects ELM mitigation in MAST plasmas, revealing that pellets can trigger ELMs and influence particle loss, with results varying depending on specific conditions.

Contribution

It provides new insights into the interaction between pellet fuelling and ELM mitigation, challenging assumptions in the ITER fuelling model.

Findings

Pellet evaporation can trigger ELMs, increasing particle loss by about 50%.

Post-pellet particle losses can be similar to non-pellet cases in some scenarios.

Counter-examples show that effects vary, indicating complex pellet-ELM interactions.

Abstract

Shallow fuelling pellets are injected from the high field side into plasmas in which ELMs have been mitigated using external magnetic perturbation coils. The data are compared with ideal assumptions in the ITER fuelling model, namely that mitigated ELMs are not affected by fuelling pellets. Firstly it is shown that during the pellet evaporation an ELM is triggered, during which the amount particle loss could be larger (factor ~1.5) than the particle loss during an ELM which was not induced by pellet. Secondly, a favourable example is shown in which post-pellet particle losses due to mitigated ELMs are similar to the non-pellet case, however unfavourable counter-examples also exist.