Code comparison of WARPXM and NIMROD in sheared-flow-stabilized Z-pinch simulations

Zap Energy is investigating the sheared-flow-stabilized Z-pinch as the core for a fusion generator. Zap has begun operating the FuZE-Q device, reaching ~700 kA pinches and more than 10⁹ neutrons per pulse.

Modeling continues to provide insight into experimental results and guides next step designs. Zap researchers are using two well-established fusion community codes, NIMROD and WARPXM, and comparing the results.

WARPXM is a discontinuous Galerkin finite element framework developed at the University of Washington to solve various plasma equation sets, including resistive magnetohydrodynamics (MHD). WARPXM allows for fully unstructured meshes (triangles and tetrahedra for 2D and 3D, respectively) to model complex geometries.

Similarly, NIMROD solves the resistive MHD equations using spectral finite elements in two dimensions and Fourier decomposition in the third (symmetry) dimension. NIMROD includes semi-implicit time advance and captures separate electron and ion temperature evolution.

Here, we present the results of the code comparison to a generic FuZE-Q scenario. Specifically, by varying the initial gas load and the applied voltage we compare the neutron yield rate and voltage/current traces between the two. The effect of two-temperature physics is also explored in NIMROD.