Electron-anode interactions in particle-in-cell simulations of applied-B ion diodes

Particle-in-cell simulations of applied-B ion diodes using the QUICKSILVER code [D. B. Seidel , in Proceedings of the Europhysics Conference on Comput ational Physics, Amsterdam, 1990, edited by A. Tenner (World Scientific, Si ngapore, 1991), p. 475] have been augmented with Monte Carlo calculations o f electron-anode interactions (reflection and energy deposition). Extractio n diode simulations demonstrate a link between the instability evolution an d increased electron loss and anode heating. Simulations of radial and extr action ion diodes show spatial nonuniformity in the predicted electron loss profile leading to hot spots on the anode that rapidly exceed the 350 degr ees C-450 degrees C range, known to be sufficient for plasma formation on e lectron-bombarded surfaces. Thermal desorption calculations indicate comple te desorption of contaminants with 15-20 kcal/mole binding energies in high -dose regions of the anode during the power pulse. Comparisons of parasitic ion emission simulations and experiment show agreement in some aspects, bu t also highlight the need for better ion source, plasma, and neutral gas mo dels. (C) 1999 American Institute of Physics. [S1070-664X(99)01408-1].