Experimental evaluation of the critical current in indium LMIS

Abstract

Depending on the emission current, a liquid-metal-ion-source produces microdroplets in addition to ions. A critical current defines the threshold of pure ion and mixed ion/droplet emission. According to previous theoretical work, this critical current depends on the liquid metal properties only. We found, that the critical current from capillary emitters is lower by about a factor of two compared with solid or porous needle emitters which are within the theoretically expected range. These results are of particular importance for applications that require pure ion emission.