Decoupling ion efficiency from impedance in pulsed power diodes

Classical axis diode theory which links the impedance of a diode to its ion production efficiency is discussed. This linkage stems from the dependence of both impedance and efficiency on the aspect ratio of the given device. This ratio is defined as the cathode outer radius, R, divided by the axial anode-cathode (A-K) gap, D. It is demonstrated that the ion efficiency, eta/sub i/, is strictly proportional only to the typical pathlength, L, of electrons in the A-K gap and that this length need not be related to R. A radial pinch reflex diode geometry is examined in which the anode is a cylindrical shell of radius, R + D and of length 2L. The decoupling of eta/sub i/ from Z/sub diode/offers new possibilities for high power/high voltage intense ion beam sources and for high power/low voltage intense electron beam sources. Numerical simulations using the PREMAS diode modeling code are completed for diode geometries which demonstrate both of these applications.