Publications

MHD modeling of conductors at ultrahigh current density

Rosenthal, Stephen E.; Desjarlais, Michael P.; Spielman, Rick B.; Stygar, William A.; Asay, J.R.; Douglas, Melissa R.; Hall, C.A.; Frese, M.H.; Morse, R.L.; Reisman, D.B.

In conjunction with ongoing high-current experiments on Sandia National Laboratories' Z accelerator (Albuquerque, NM) we have revisited a problem first described in detail by Heinz Knoepfel. Unlike the 1-Tesla MITL's of pulsed power accelerators used to produce intense particle beams, Z's disk, transmission line (downstream of the current addition) is in a 100-1200-Tesla regime; so its conductors cannot be modeled simply as static infinite conductivity boundaries. Using the MHD code [2], [3], [17] MACH2 we have been investigating the conductor hydrodynamics, characterizing the joule heating, magnetic field diffusion, and material deformation, pressure, and velocity over a range of current densities, current rise-times, and conductor materials. The three purposes of this work are 1) to quantify power flow losses owing to ultrahigh magnetic fields, 2) to model the response of VISAR [4], [18], [19] diagnostic samples in various configurations on Z, and 3) to incorporate the most appropriate equation of state and conductivity models into our magnetohydrodynamics (MHD) computations. Certain features are strongly dependent on the details of the conductivity model.