Sandpile modelling of pellet pacing in fusion plasmas

TL;DR

This paper modifies a sandpile model to simulate plasma edge behavior, demonstrating that continuous high fueling reduces large avalanches more effectively than pellet pacing, offering insights into ELM control strategies.

Contribution

It introduces a modified sandpile model with increased and intermittent driving to analyze plasma edge behavior and ELM control.

Findings

High continuous driving reduces largest avalanches more than pellet pacing.

Analytical determination of sandpile behavior at high driving.

Implication that increased fueling may be more effective for ELM control.

Abstract

Sandpile models have been used to provide simple phenomenological models without incorporating the detailed features of a fully featured model. The Chapman sandpile model Chapman et al Physical Review Letters 86, 2814 (2001) has been used as an analogue for the behaviour of a plasma edge, with mass loss events being used as analogues for ELMs. In this work we modify the Chapman sandpile model by providing for both increased and intermittent driving. We show that the behaviour of the sandpile, when continuously fuelled at very high driving, can be determined analytically by a simple algorithm. We observe that the size of the largest avalanches is better reduced by increasing constant driving than by the intermittent introduction of `pellets' of sand. Using the sandpile model as a reduced model of ELMing behaviour, we conject that ELM control in a fusion plasma may similarly prove more effective with increased total fuelling than with pellet addition.