Neutron bombardment of tungsten plasma-facing components (PFCs) in fusion reactors is known to create helium bubbles, which can lead to embrittlement and material degradation. However, recent investigations at ITER suggest that this helium accumulation might offer a novel method for active plasma control. The accumulation of helium within the tungsten divertor is being studied for its potential to modify plasma transport properties, possibly leading to improved confinement and stability.

This research stems from observations during experiments on other fusion devices where helium injection was used to influence plasma behavior. The ITER team is now analyzing how the in-situ generation of helium from neutron activation of tungsten could provide a continuous and self-regulating mechanism for plasma control. This approach could reduce the need for external gas puffing or other active control systems, simplifying reactor operation and maintenance.

This research stems from observations during experiments on other fusion devices where helium injection was used to influence plasma behavior.

The primary concern with helium in fusion reactors has historically been its role as an impurity that can dilute the D-T fuel and reduce fusion power output. However, the controlled accumulation of helium within the PFCs, rather than its presence in the core plasma, presents a different scenario. The ITER divertor, designed to handle extreme heat and particle fluxes, is a critical area where such effects are being closely monitored and modeled.

Understanding the precise relationship between neutron flux, helium bubble formation kinetics, and the resulting impact on plasma edge conditions is crucial. ITER's advanced diagnostic capabilities, including materials analysis and plasma spectroscopy, will be instrumental in validating these theoretical models. The goal is to quantify the extent to which helium accumulation can beneficially alter plasma parameters such as radiation losses and particle transport.

If successful, this discovery could represent a significant shift in how fusion reactor PFCs are designed and operated, transforming a potential material challenge into an operational advantage. Further experimental campaigns at ITER will focus on correlating specific neutron fluences and operating conditions with measurable changes in plasma performance attributable to helium accumulation in the tungsten divertor. Source: ITER