ArbiTER: A Flexible Eigenvalue Solver for Edge Fusion Plasma Applications

Research in fusion energy is becoming increasingly reliant on large-scale plasma simulations for both scientific understanding and hardware design. While most such codes evolve equations in time, there is a small but significant class of important problems that are susceptible to linear and/or quasilinear analysis. In such cases, eigenvalue solvers offer considerable advantages in computational efficiency over time-stepping codes. In addition, their relative simplicity makes them useful for verification of their time-stepping counterparts. In our past work, we developed the 2DX eigenvalue code for problems in edge plasma physics involving fluid models in an Xpoint topology, with the additional ability to approximate some kinetic models. Here, we propose extending the capabilities of the 2DX code to create an eigenvalue solver capable of simulating a wide range of physics models with nearly arbitrary topology and dimensionality: the Arbitrary Topology Equation Reader (ArbiTER) code. This code would be capable of finding eigenvalues in plasma physics models ranging from one or two dimensional fluid systems to five dimensional gyrokinetic systems as well as intermediate cases. It would moreover be able to do so in X-point as well as more complicated topologies, such as the asymmetric double null or snowflake divertor tokamak topologies. In the Phase I proposal, we will demonstrate the feasibility of this code in three critical areas: (i) numerical implementation of a topology parser with sufficient flexibility to permit its intended applications, (ii) benchmarking tests with 2DX and BOUT, and (iii) code timing to determine the computational requirements for high dimensionality models. Commercial Applications and Other Benefits: Limited funding available to the development teams for the edge turbulence simulation projects in the US has resulted in even more limited resources being available for verification and benchmarking studies. The proposed linear code suite will fill a unique niche in the fusion energy program, both in the US and international fusion communities, and is suitable for government sector follow-on funding