Modeling helium compression and enrichment in DIII-D edge plasmas using the SOLPS-ITER code

TL;DR

This paper uses the SOLPS-ITER code to model helium behavior in DIII-D edge plasmas, providing insights into helium transport, recycling, and enrichment crucial for fusion reactor design and tritium fuel efficiency.

Contribution

It offers a detailed numerical analysis of helium dynamics in the edge plasma of DIII-D, evaluating the applicability of the Tritium Burn Efficiency metric for fusion reactor planning.

Findings

Helium enrichment occurs in the divertor region.

Helium transport is complex and differs from other impurities.

TBE assumptions may need refinement based on simulation results.

Abstract

Efficient removal of helium ash is a critical requirement for the operation of fusion power plants, as its accumulation can dilute the core fuel and degrade plasma performance. While past studies suggested that helium exhaust in burning plasmas could be managed effectively through divertor optimization and conventional cryopumping, a detailed understanding of helium behavior in the edge and divertor plasma remains limited, as helium transport through the edge plasma is complex and fundamentally different from other impurity species. With the emergence of more sophisticated numerical modeling tools and renewed focus on D-T burning plasmas, revisiting helium transport in current magnetic confinement devices is necessary for planning and designing fusion pilot plants. This study uses SOLPS-ITER to model a helium-seeded discharge from the DIII-D tokamak, analyzing the transport, recycling, and enrichment of helium in the divertor. In addition to characterizing helium dynamics, the results are interpreted in terms of the Tritium Burn Efficiency (TBE), a recently proposed metric linking helium exhaust fraction to tritium fuel utilization in steady-state burning plasmas. By assessing the compatibility of TBE assumptions with detailed edge plasma simulations, this work provides insight into the practical viability of TBE as a reactor design and performance metric.