부산대학교 도서관

The azimuthally periodic Z pulsed power facility at Sandia National Laboratories drives megajoules of electrical energy stored at its outer perimeter through a set of radially-convergent parallel transmission lines towards a load at the machine center. The individual line currents are combined in a double post-hole convolute configuration to deliver peak currents up to 26 MA over an ∼ 150 ns pulse width (terawatts). This power flow is associated with a vastness of scales in time (discharge length versus electron cyclotron frequencies), space (transmission line lengths versus electron gyroradius), and velocity (outgassed neutrals versus the propagation speeds of the EM waves in each medium), as well as highly coupled multi-physics which make straightforward numerical approaches not viable. Heterogeneous methods are required. In this talk, we overview our model which bridges the distinct regions in the Z accelerator, i.e. the upstream water/vacuum sections carrying EM waves to the downstream vacuum region comprised of magnetically-insulated transmission lines where crucial 3D effects from emitted particles must be included to predict the power flow characteristics and load current correctly. This complex 3D region spans the kinetic low density plasma regime to high field regions near the load containing high density, highly collisional plasmas. We showcase results from detailed 3D kinetic simulations incorporating electromagnetic wave propagation, relativistic plasma dynamics, field-emitted electrons, and self-consistent surface heating with neutral desorption physics using an in-house particle-in-cell code, EMPIRE, provide cross-code comparisons with results from CHICAGO 1 , and compare with measurements from actual Z shots.