Magnetic Mode Analysis in the Zap Flow-Stabilized Z-Pinch Experiment

摘要

The Zap Flow-Stabilized Z-pinch experiment at the University of Washington studies the stabilizing effects of sheared flow on a Z-pinch. An internal eight-probe azimuthal array is used to measure the magnetic field. Fourier analysis of the magnetic field yields information on the structure of the plasma. The m=1 mode is related to the radial offset of the plasma, while the m=2 mode is related to the elongation of the plasma. Using this information, a non-linear fitting routine was developed to determine the radial position and structure of the plasma. The plasma is simulated as two independent current- carrying filaments. To improve speed and accuracy, a neural net was developed. The neural net attempts to simulate the non-linear fit as closely as possible while performing at speeds up to twenty times faster. Unlike a non-linear fitting routine, the neural net requires no initial guesses, and thus runs independently of the user. Testing of both the neural net and the non-linear fitting routine show that both techniques compute results which fit the experimental m=1 data well. Both techniques display similar error, although the neural net is less accurate during periods is which the plasma is unstable. Further work is being done to improve the calculation of the separation between the two filaments.