The DOE Office of Science recently published a highlight, “Cooling Fusion Plasmas from the Inside Out,” about simulations done by Val Izzo to understand a new method that uses boron-filled diamond shells to quickly cool fusion plasmas. The technique uses a diamond shell that ablates slowly as it passes through the edge of the plasma and then breaks open in the center to release a larger quantity of boron, initiating the quench internally. This cools the inner layers first, so that the released heat is still trapped by the outer layers as it is converted to radiation. The simulations show that both the total amount of ablated carbon from the diamond shell and the location at which the shell breaks open determine whether the outer flux surfaces survive while the center of the plasma cools. The simulations also show this type of quench has the unexpected benefit of preventing runaway electrons. The highlight is available on https://www.energy.gov/science/listings/science-highlights and will be published soon at https://www.eurekalert.org/doe/ and https://www.newswise.com/doescience/ .

Several members of the Theory Group presented remotely at the IAEA Meeting this week. Gary Staebler gave an Overview talk on “Advances in Prediction of Tokamak Experiments with Theory-Based Models” and Emily Belli delivered an Oral talk on “Strong Reversal of Simple Isotope Scaling Laws in Tokamak Edge Turbulence”. Four poster presentations were exhibited. Charlson Kim showed work on “Simulations and Validation of Disruption Mitigation and Projections to ITER’s Disruption Mitigation System”, and Yueqiang Liu on “Towards Prediction of ELM Control by RMP in ITER Based on Linear and Quasi-linear Plasma Response”. Joseph McClenaghan contributed a poster on “Validation of Pellet Ablation Models and Investigation of Density Fueling Needs on ITER and CFETR”. Jerome Guterl showed the “Progress toward Predictive Modeling and In-situ Monitoring of Tungsten Net Erosion in Tokamak Divertor” made by the group.

A module to compute plasma resistivity in dense, partially ionized and partially magnetized plasmas, which are relevant for inertially confined plasmas, has been implemented in the ALMA code. In this regime, Fermi-Dirac statistics and quantum effects must be invoked in order to account for the degeneracy of the electron population, which in turn has strong effects in the forces felt by colliding particles. Additional effects involve accounting for the partial ionization of the plasma. The model implemented follows a classic reference by Lee, More, and Desjarlais, and paves the way towards ALMA MHD simulations of Thermo-Electric Instabilities believed to be involved in processes limiting implosion target yields.