A fully engineered liquid metal field emission source of gold ions has been developed, operating with low heater power (<30 W) and without forced cooling. The design and performance of the source are described in detail. The present design can also be used to produce sources of a variety of elements, other than gold, including tin, bismuth, and lead. It provides a versatile and reliable research tool which is fully compatible with ultrahigh vacuum installations. Potential fields of application include materials development and surface analysis.