Atomistic Modeling of the Plasma-Material Interaction for a Sheared-Flow-Stabilized Z Pinch

The plasma-facing components (PFCs) in Zap Energy’s sheared-flow-stabilized Z-pinch devices [Levitt et al., Phys. Plasmas 30, 090603 (2023)] will experience pronounced heat and particle fluxes, especially as these devices are driven toward Q>1 conditions. Previously it has been shown that heat loads to the cathode and anode can exceed 10 GW/m². During multi-microsecond discharges, this load can lead to the sublimation of graphitic materials. Particle fluxes to PFCs are estimated by assuming that 10% of the Bohm fluxes for a presently achievable as well for a Q = 1 Z-pinch plasma will arrive at the surface, leading to estimates of the surface flux in the range of 10²⁷ – 10³⁰ D m-2 s-1.  

 

To better grasp graphite PFC response to such extreme conditions, molecular dynamic (MD) simulations were undertaken. LAMMPS [Thompson et al., Comp. Phys. Comm. 271, 108171 (2022)] was selected as the MD solver, using ReaxFF interatomic potentials. Surface slabs of graphite and amorphous deuterated-carbon were cumulatively bombarded by 1-keV D atoms. The simulations were designed to match the expected fluxes up to 0.1% of the estimated fluences during a pulse. Changes to material properties and the Equation of State are compared where appropriate.