Access and sustainment of ELMy H-mode operation for ITER Pre-Fusion Power Operation plasmas using JINTRAC

TL;DR

This study uses integrated modelling to assess the power requirements for stable ELMy H-mode operation in ITER using hydrogen and helium plasmas, suggesting that 30 MW of ECRH may be needed for hydrogen but less for helium mixes.

Contribution

It provides the first detailed integrated core and edge modelling analysis of ELMy H-mode access in ITER hydrogen and helium plasmas, informing power system requirements.

Findings

30 MW ECRH likely needed for hydrogen plasmas

Helium fraction reduces L-H power threshold

Stable H-mode possible at 20 MW with helium admixture

Abstract

In the initial stages of ITER operation, ELM mitigation systems need to be commissioned. This requires controlled flat-top operation in type-I ELMy H-mode regimes. Hydrogen or helium plasma discharges are used exclusively in these stages to ensure negligible production of neutrons from fusion reactions. With the expected higher L-H power threshold of hydrogen and helium plasmas compared to corresponding D and D/T plasmas, it is uncertain whether available auxiliary power systems are sufficient to operate in stable type-I ELMy H-mode. This has been investigated using integrated core and edge/SOL/divertor modelling with JINTRAC. Assuming that the L-H power threshold is well captured by the Martin08 scaling law, the presented simulations have found that 30 MW of ECRH power is likely required for the investigated hydrogen plasma scenarios, rather than the originally planned 20 MW in the 2016 Staged Approach ITER Baseline. However, past experiments have shown that a small helium fraction (~10 %) can considerably reduce the hydrogen plasma L-H power threshold. Assuming that these results extrapolate to ITER operation regimes, the 7.5MA/2.65T hydrogen plasma scenario is likely to access stable type-I ELMy H-mode operation also at 20 MW of ECRH.