Extraction ion diode studies for optimized performance: Divergence, ion species, and parasitic load

Recent advances worldwide in pulsed ion beam generation with magnetically-insulated ion diodes in annular extraction geometry have brought several issues to the forefront in the search for optimal performance from these diodes. Beam divergence, ion species composition, and diode impedance and power coupling behavior are all issues of central concern in obtaining the best possible beams from these sources. The LION pulser(1.2 MV, 4 Ω, 40 ns) at Cornell University has been used to investigate several aspects of these issues. The basic experimental approach is to vary diode operating parameters, and to diagnose the resulting changes in diode performance. The LION diode is shown in Fig. 1. Diagnostics include beam current density(magnetically-insulated Faraday cups), ion species-resolved beam divergence(Rutherford-scattering shadow boxes), ion species and energy composition (Thomson parabola spectrometer, Rutherford-scattering magnetic spectrometer), diode voltage and current diagnostics(rogowskii and B-dot current monitors, inductive divider and electron-launching voltage monitors), electron loss detection( collimated bremsstrahlung detectors and in-anode collectors), and in-gap light emission( visible light streak photography and emission spectroscopy).