Publications

Current transport and loss mechanisms in the Z accelerator

Bennett, N.; Welch, D.R.; Jennings, C.A.; Yu, E.; Hess, Mark H.; Hutsel, B.T.; Laity, G.; Moore, James M.; Rose, D.V.; Peterson, K.; Cuneo, M.E.

A challenge for the TW-class accelerators driving Z-pinch experiments, such as Sandia National Laboratories' Z machine, is to efficiently couple power from multiple storage banks into a single multi-MA transmission line. The physical processes that lead to current loss are identified in new large-scale, multidimensional simulations of the Z machine. Kinetic models follow the range of physics occurring during a pulse, from vacuum pulse propagation to charged-particle emission and magnetically-insulated current flow to electrode plasma expansion. Simulations demonstrate that current is diverted from the load through a combination of standard transport (uninsulated charged-particle flows) and anomalous transport. Standard transport occurs in regions where the electrode current density is a few 104-105 A/cm2 and current is diverted from the load via transport without magnetic insulation. In regions with electrode current density >106 A/cm2, electrode surface plasmas develop velocity-shear instabilities and a Hall-field-related transport which scales with electron density and may, therefore, lead to increased current loss.