Optimum neutralization of negative space charge in cylindrical and spherical diodes

Elevation of the space-charge-limited electron current in cylindrical and spherical diodes, brought about by the introduction of neutralizing positive ions between the electrodes, is considered. The ion distribution is chosen to belong to the particular mathematical class that enables one of the three successive integrals of Poisson´s equation to be performed analytically. For the external cathode configuration, it is found that there is no upper limit to the electron current provided there is sufficient ion generation and provided the power supply can give sufficient current. These results are applied, for the enhancement of current, to the electron-beam-pumped excimer laser in cylindrical symmetry and a suitable means of generating the required ion production is suggested. In the internal cathode configuration the limited electron current can be increased severalfold by the introduction of ions. However, an upper limit is reached when the electric field is reduced to zero at some point between the electrodes