Conversion of intense electron beam energy into converging ion fluxes - Theoretical studies

Various designs of relativistic electron beam diodes allow the production of very intense converging ion pulses^† for bombardment of, e.g., pellet or rod targets placed inside a mesh anode. Ions formed by ionization of anode mesh material are accelerated by the self-consistent space charge produced by electrons from the cathode and target. In the conventional region of the diode before the anode, the self-pinching of the electron flow largely decouples the ion acceleration region from the electron source, so that the space charge does not quench the electron current. The steady-state equations for the magnetic field-free ion-acceleration regions of such diodes are analyzed in several goemetries, and the formation and effects of virtual cathodes are discussed. Efficient conversion (>;50%) of electron current into ion current is predicted.