Numerical modeling of an end‐plugged theta pinch

• Published in: The Physics of fluids (1958) 1981-02, Vol.24 (2), p.339-346
• Main Authors: Milroy, Richard D., Steinhauer, Loren C.
• Format: Article
• Language: English
• ISSN: 0031-9171; 2163-4998
• DOI: 10.1063/1.863373

Analytical and numerical studies of an end‐plugged theta pinch are described. The analytical model treats the ablated plug plasma in the quasi‐static limit where radiation losses balance energy flowing from the main plasma. This model is used to calculate the enhancement in energy confinement due to an ablating end plug for various plug species. The numerical model employs a one‐dimensional, time‐dependent magnetohydro‐dynamic code. Results of calculations simulating the Scylla IV‐P end‐plugged theta pinch experiment are presented. The calculations achieve good agreement with the observed decay time of the energy line density. Moreover, the observed tendency toward longer decay times at lower atomic number is also predicted. However, certain notable discrepancies are found. For Si plugs, the calculations indicate a somewhat longer decay time than observed with SiO2 plugs. In addition, an axial compression wave driven by plug ablation causes the calculated energy line density to rise after 15 to 20 μsec which was not observed in the experiments. This is believed to be a feature of the one radial cell model which forbids axial wave dispersion; such dispersion would tend to mute the appearance of such waves. For fusion reactor scale plasma, the calculations predict that higher atomic number leads to negligible enhancements in confinement time.