A plug‐in module bearing 14–20 tungsten filament emitters has been developed for use with the field‐free neutral beam sources to be employed in the Tara tandem mirror experiments. Eight such modules constitute the total distributed cathode for one source. Each module has its own plug‐in power connector, and may be removed from the source assembly as a unit, independently of the outer modules. The plug‐in approach to construction results in a reduction both in the cost to build the source and in the time required for routine servicing and filament replacement. Plasma profiles are the same as in conventionally engineered sources of the same geometry.