Description
The US Fusion Roadmap envisages the first fusion power plants to be delivered by the private sector. This goal requires major advances not only in the plasma core, which must be demonstrated with much better energy confinement, control and power handling than attained today, but also in a range of even more challenging technology innovations. And the compatibility between these techniques, which interact with and constrain each other, must be resolved, as well as their projection to the reactor scale. The strength of publicly funded facilities is that they have broad capabilities to experiment, learn what works, and understand how to project and integrate solutions – to discover the path.
DIII-D has pivoted its program to address the critical requirements to meet this agenda. To assess new fusion technologies, DIII-D is upgrading its heating, current drive and shaping capabilities to provide relevant conditions in terms of collisionality, opacity, , rotation, plasma equilibration and current distribution (figure right). This enables key tests of behaviors such as heat dissipation, flows, impurity dynamics, pellet ablation, RF deposition, 3D fields, or measurement and control – to understand the plasma interactions of a range of technologies. It also enables the facility to determine which core solutions are most compatible and advantageous, ranging from high current pulsed scenarios to ‘steady state’ noninductive, extreme positive to negative triangularity, and broad to peaked current profiles.
Based on this, DIII-D is pursuing an aggressive program of technology development. Most critical is exhaust handling to protect the first wall, where we are pursuing a modular series of divertors (above) to isolate and enhance detachment of a cold plasma edge through magnetic shaping, closure and radiative impurity techniques. DIII-D is then exploring novel wall materials, with 61 tested in the last 2 years (below), ranging from advanced tungsten alloys to high temperature ceramics, and even pebble and liquid metal structures. Three new current drive technologies have been pioneered: high field side lower hybrid current drive (CD), helicon ultrahigh harmonic fast wave, and top launch electron cyclotron CD. Pellet innovations have been developed to fuel and safely quench fusion plasmas. Pioneering diagnostic technologies have facilitated a spin-out of a private company, Nusenics, and tests for several others. And DIII D is now pioneering AI digital twin technology to accelerate research and close the loop on plasma control.
These elements combine with an opening up of the facility to private sector engagement with 19 private fusion companies now exploiting DIII-D to test critical elements of their approach. DIII D is thus providing unique and critically needed data for the fusion commercialization agenda.