Extraction geometry ion diode physics: Theoretical modeling and experimental results

The LION accelerator has been used to perform a series of experiments to investigate the operation of magnetically insulated extraction diodes. These diodes produce annular beam with an outer radius of 11.3 cm and an inner radius of 8.6 cm. The beam voltages were typically 1-1.25 MV with a 40 nsec ion beam current of approximately 250 KA 8. The diodes were normally operated at B/B* ≈ 1.5 and typical enhancements over Child-Langmuir of 15 to 25. Both active and passive anode plasma sources have been investigated. The effects of modifying the magnetic field gradient in the diode will be discussed and a theoretical model presented. Techniques for cleaning the anode surface for the production of Li beams will be described.