Experimental and simulation study of argon plasma transport in MPS-LD to increase electron density at target

The multiple plasma simulation linear device (MPS-LD) device aims to experimentally simulate tokamak divertor plasma and its interactions with plasma-facing materials. To achieve this objective, improving target plasma parameters by understanding plasma transport characteristics is essential. In this work, both experimental and simulation studies of argon (Ar) plasma transport are carried out, with a focus on investigating the physical methods and mechanisms for increasing target electron density ( n et ). In the experiments, Langmuir triple probes and optical emission spectroscopy are employed to diagnose plasma parameters. SOLPS-ITER is utilized to conduct corresponding numerical simulations. First, SOLPS-ITER simulations are compared with experimental results to demonstrate the accuracy of the physical model. After the simulation validation, subsequently, by moving the target axially, the effects of target positions ( Z ) on n et and particle flux density ( Γ t ) are investigated through the combination of experimental and numerical approaches. The results demonstrate that both n et and Γ t show a nearly linear increase as Z decreases. This phenomenon is explained by the reduction in radial particle transport losses, as revealed by particle balance analysis. Based on the analysis, a method is proposed to further increase n et by enhancing plasma confinement via adjusting the target magnetic field strength ( B tar ) to establish different magnetic field configurations. The corresponding experimental and simulation results show that increasing B tar effectively enhances n et , particularly in the axis region, accompanied by an increased radial density gradient. This improvement is because the enhanced B tar leads to a significant reduction of radial particle losses. Meanwhile, the intensified B tar induces convergence of magnetic field lines toward the axis, promoting plasma transport into the axis region. By optimizing the target positions ( Z shortened from 3 m to 1.68 m) and magnetic field configurations ( B tar increased from 0.1 T to 0.25 T), n et is significantly increased by more than fivefold. This work deepens the comprehension of Ar plasma transport mechanisms and provides feasible solutions for achieving higher n et .