Studies of conditions in detail in magnetically insulated intense ion beam diodes

In order to better understand the operation of magnetically insulated diodes, we have performed and are performing detailed studies of conditions within these diodes. Electron and ion flow and their correlation have been studied locally in the LONGSHOT diode (≲100 kV, 700 ns). The observed correlations made it possible to differentiate among three classes of ion deflections. Results imply the presence of transverse electric fields in the diode caused by changes in the shape of the anode plasma surface (two classes) or by cathode plasma processes (the third class). In experiments on a 50 ns, 400 kV diode generating ∼125 A/cm² ion current density from a surface flashover anode, an average electron density of ∼10¹⁵/cm³ in the anode plasma was inferred from Stark (density) broadening of the hydrogen Hβ line. Preliminary measurements of ion transverse velocities obtained from the Doppler Broadening of optical emission from ions in the gap of a 400 kV, 300 ns ion diode have indicated a mean transverse energy of ∼100 eV, increasing with the distance from the anode.