Theory Weekly Highlights for April 2020

April 24, 2020

OMFIT v2.2 has been released, including many extensions, improvements, enhancements, and bugfixes. This is the last version of OMFIT which supports both Python 2 and Python 3. Going forward support for the now obsolete Python 2 will be progressively dropped, which will result in leaner source code that will simplify maintenance. As part of this effort, OMFIT developers are making plans for refactoring the framework API, making it consistent throughout. Although these changes will likely break some backward compatibility in the short term, the long-term benefits for the overall OMFIT endeavor are overwhelming, and users will still be able to open old projects with OMFIT v2.2.

April 10, 2020

A two-hour discussion on the role of the US in the ITER integrated modeling (IM) program was held remotely as part of the yearly DoE AToM - SciDAC all-hands meeting on April 1st and 2nd. Over 80 people joined via Zoom, including involvement from both international and ITER participants. The meeting covered technical aspects of the ITER integrated modeling and analysis suite (IMAS), as well as high level considerations about how both the US and ITER fusion programs could benefit from stronger engagement with each other. The meeting concluded with a general consensus on the need for dedicated resources and a higher level of coordination of US interaction with the ITER IM program beyond IMEG, US-BPO, and AToM. The findings of the meeting were reported to the DoE fusion managers.

April 03, 2020

A novel analytic isotope scaling law has been proposed to describe the electron-to-ion mass ratio dependence of turbulent ion and electron energy fluxes in both ion-dominated core and electron-dominated edge transport regimes. The mass-ratio dependence arises from the nonadiabatic response associated with the fast electron parallel motion. The nonadiabatic electron drive strongly regulates the turbulence levels and plays a key role in altering - and in the case of the DIII-D edge, reversing – the naive gyroBohm scaling. In the reversed regime, hydrogen energy fluxes are larger than deuterium fluxes, which is the opposite of the naive prediction. The finite-electron mass correction is larger for light ions like hydrogen and larger safety factor so that, while it is weak in the core, it dominates the mass scaling in the edge. These results have implications for lowering the power threshold for the L-to-H mode transition in a reactor like ITER and could advance theoretical-based global energy confinement isotope scaling toward agreement with experimental observations.

These highlights are reports of research work in progress and are accordingly subject to change or modification