Finite Element Modeling for Megagauss Magnetic Field Generation

Summary form only given. Applying external magnetic fields with megagauss strength is needed for hot plasma confinement and stabilization, with applications from laboratory astrophysics to radiation sources to fusion. We investigate the possibility of generating ultra-high magnetic fields with the fast Z-pinch generator "Zebra" for experiments at the NTF. The high impedance generator can drive into a load a current with a peak of 1 MA and a rise time of the order of 100 ns. To design appropriate loads we use Femlab and Screamer to simulate the magnetic field. Screamer accurately predicts the load current using a detailed model of Zebra and helps optimize the Zebra operation for any given inductive load. Using the current obtained from Screamer, Femlab is able to calculate the magnetic field, heating, and stress on the conductor. During the first hundred nanoseconds the resistive heating causes changes in material properties and potentially state transformations. Most importantly, the resistivity increases within the skin depth enhancing the magnetic field diffusion. In addition, the magnetic field pressure produces structural deformation in the load, which is enhanced due to heating. All these effects must be taken into consideration to determine the integrity of the coil until maximum field is reached. The presentation will include simulation results for single- and multi-turn coils, as well as quasi-force-free inductors