Energetic Materials As Ion Sources For Pulsed Power Diodes

Thin coatings of energetic (unstable) chemicals on anodes of pulsed ion diodes may improve diode performance. We present preliminary data from the LION accelerator at Cornell and from the PBFA II accelerator at Sandia. Suggested mechanisms for ion creation include: bombardment by electrons, negative ions, or photons; growth of ion field emission whiskers; dielectric flashover or electric field liberation of a neutral layer that subsequently ionizes; and trapped electron clouds heated by RF radiation from the transmission line and diode structure. These possible mechanisms may impart a microstructure in the anode plasma due to either intrinsic microstructure in the energy source or to the nucleation properties of materials undergoing rapid phase changes. A surface of unstable molecules should more promptly decompose and create a denser and more uniform layer of gas during the leading portions of the pulse; a shorter time interval is required to start gas evolution from adjacent points that might be subject to differences in incident energy or might vary in local material morphology. We assume that the unstable surface is very thin and that propagating explosion does not occur; rather, the initiating energy comes from external sources so that the internal structure of the unstable surface does not greatly influence the expansion energy. Once a uniform layer of sufficiently dense gas is generated, ionization will proceed rapidly in the diode electric field.