Two-fluid modeling of linear and nonlinear stability of the sheared-flow-stabilized Z pinch

Five-moment two-fluid modeling is used to generate new insight into stability of the sheared-flow-stabilized Z pinch. Simulation results [1] identify linear and nonlinear behaviors that may enable long-lived quiescent Z-pinch plasmas. In sheared plasmas that are linearly unstable, nonlinear relaxation leads to stable quasi-equilibrium conditions in both 2D and 3D simulations. Key features of previous PIC results for linear stability are reproduced, opening the possibility of whole device modeling with physical fidelity comparable to kinetic simulations. Modeling is done in the high-order discontinuous Galerkin WARPXM framework [2], beginning from Bennett equilibrium profiles that approximate observed plasmas in the FuZE experiment. Instability growth rates, with varying degrees of radially sheared axial flow, agree closely with prior results for linear growth. In the nonlinear phase of the instabilities, sub-Alfvenic sheared flow drives mixing that yields quasi-equilibrium conditions. Such quasi-equilibria provide a cornerstone for more completely understanding and exploiting sheared-flow stabilization of the Z pinch as it is scaled toward fusion reactor conditions.

[1] Meier and Shumlak, Phys. Plasmas 28, 092512 (2021)

[2] Shumlak et al., Comput. Phys. Commun. 182, 1767 (2011)