Development of a 5N-moment Multi-Fluid Plasma Model for D-T Fusion in an Axisymmetric Z Pinch

Abstract

The thermonuclear fusion process in a D-T Z pinch is investigated by developing the multi-component, deuterium-tritium-helium-electron, model including fusion reactions and interspecies collisions via the WARPXM simulation framework. The geometric source terms are implemented into WARPXM to solve axisymmetric problems in cylindrical coordinates without changing the code’s infrastructure. The 5N-moment growth rates peak at the expected wavenumber and further stabilize at large wavenumbers in a manner that agrees with previously published studies using higher fidelity kinetic models. The radially-sheared axial flow, ∂rvz ̸= 0, stabilizes the sausage instabilities significantly as observed in the Fusion Z-pinch Experiment (FuZE) at the University of Washington. Braginskii viscosity and thermal conductivity also indicates the stronger stabilizing effects with decreasing plasma collisionality. The energetic alphas produced in the core of the Z-pinch plasma expand radially and interact with the azimuthal magnetic field, which drives an axial current of alpha particles. The primary energy cascade initiates from energetic alphas to electrons, and eventually the electron energy transfers to the ions. The increase in fusion gain becomes significant when the plasma pinch current exceeds 1.35 MA, which corresponds to a pinch radius equal to the gyroradius of a D-T fusion alpha. While never reaching ignition, the fusion gain increases from 8.14 to 151.8 with the increasing pinch current and 7% of the alpha heating fraction.