Lang Lao attended and chaired the 10th ITER Integrated Modeling Expert Group (IMEG) Meeting at ITER Headquarters, Cadarache, France November 26-28, 2018. The main goal of the IMEG meeting is to review progress since the last meeting and to advise ITER on its Integrated Modeling (IM) Program to develop an Integrated Modeling Analysis Suite (IMAS) and an infrastructure to support ITER plasma operation and research. Sterling Smith also attended the IMEG Meeting as a domestic participant. For this year's meeting, IMEG was also requested to identify short-term IM projects of benefit to ITER and Members’ programmes with focused deliverables that support or complement the IO’s identified IM needs.

Most of the GA Theory staff participated in the 60th Annual APS Division of Plasma Physics Meeting in Portland, Oregon from November 4 through November 9, with 14 staff and collaborators attending. Jeff Candy, Charlson Kim, and Rui Ding gave invited talks. Candy presented work on “Theoretical requirements for calculating heavy impurity transport in rotating plasmas.” Charlson Kim described the recent work on “Shattered Pellet Injection Simulations with NIMROD,” and Rui Ding showed results from “Modeling of plasma-wall interaction in tokamak experiments with high-Z materials.”
Alan Turnbull attended the combined 23rd Workshop on MHD Stability Control and US Japan Workshop held at UCLA November 12 through 14. In accordance with the theme of the workshop, Alan presented some “Reflections on Control Issues for Tokamaks and Stellarators”, describing the Advanced Tokamak as a highly optimized feedback-controlled system, in comparison to a stellarator or conventional tokamak.

An innovative approach to uncertainty quantification for transport modeling using a polynomial chaos expansion has been tested with applications to TGLF modeling of DIII-D ITER baseline plasmas. The methodology (which has been implemented in the OMFIT TGLF_SCAN module) allows for efficient propagation of multivariate probability distribution functions (PDFs) of uncertain parameters into PDFs of model predictions. For the specific plasmas modeled, a clear difference in the parametric sensitivities of the turbulent fluxes was found between plasmas with only neutral beam heating (NBI), and neutral beam plus electron cyclotron heating (NBI+ECH). The change is consistent with a transition from ITG-dominated transport to multi scale ITG+ETG turbulence as the heating sources are changed from NBI to NBI+ECH. A new set of validation metrics appropriate for probabilistic comparisons was developed. A paper on this work: “Propagation of input parameter uncertainties in transport models” by P. Vaezi et al. was just published in Physics of Plasmas (https://doi.org/10.1063/1.5053906).