Ir - Ce cathodes as high-density emitters in electron beam ion sources

Abstract

In electron beam ion sources (EBIS/T) cathodes with high current densities are of great interest. Commonly used cathodes like impregnated tungsten cathodes and cathodes emit current densities of 10 and 100 A , respectively. In order to obtain high electron beam current densities of for the stepwise ionization of few-electron, high-Z ions [] or for the fast production of low-Z bare nuclei, the electron beam compression has to be very high using these cathodes. A high beam compression increases the beam temperature, which limits the current density. High current densities are also limited by the magnetic flux through the cathode. The application of small highly emissive cathodes, like Ir - Ce cathodes, reduces the magnetic flux through the cathode, so that a magnetic shield of the emitter is no longer required. By emitting relatively high currents from these small cathodes, hence emitting high emission current densities, the desired beam current densities can be attained by a moderate beam compression.