A publication of the Office of Advanced Simulation & Computing, NNSA Defense Programs
NA-ASC-500-07—Issue 4
September 2007
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Progress on simulating wire-array Z pinch implosions
A Sandia team has implemented a mass inflow boundary condition into the ALEGRA High Energy Density Physics code, which has allowed researchers to make significant progress in the study of Z pinches. A wire-array Z pinch is an annular array of tiny metal wires (~10 micron diameter) which, when pulsed with current, is subject to a magnetic force that implodes the pinch. The resulting stagnation and thermalization of the pinch on the cylindrical axis of symmetry yields a copious amount of x-rays, thus making the Z pinch an attractive radiation source. The first 50 to 80% of the Z pinch lifetime is described by a mass ablation phase, during which stationary wire cores cook off material that is subsequently swept towards axis by the magnetic field, thus resulting in a radial redistribution of mass. The ablation phase is difficult to simulate because it is both fully 3-dimensional (3D) in nature and requires very high resolution to model the small diameter wires.
The new mass inflow boundary condition models the ablation phase as a boundary condition, thereby allowing researchers to focus on the ensuing implosion phase. Z pinch simulations using the mass inflow model have produced the best comparison to date with experimental x-ray powers and radiographic images. Also, significant qualitative understanding has been made regarding the importance of 3D effects on the implosion.
An example simulation of a Z pinch implosion using the mass inflow model, illustrating the highly 3D nature of the pinch.
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Last Modified September 27, 2007
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