An ion source with a crucible is disclosed. In some embodiments, the crucible contains a solid dopant material, such as a metal. A porous wicking tip is disposed in the crucible in contact with the solid dopant material. The porous wicking tip may be a tube with one or more interior conduits. Alternatively, the porous tip may be two concentric cylinders with a plurality of rods disposed in the annular ring between the two cylinders. Alternatively, the porous tip may be one or more foil layers wound together. In each of these embodiments, the wicking tip can be used to control the flow rate of molten dopant material to the arc chamber.