A cathode apparatus for an ion source has a cathode with a positioning feature and a blind hole. A cathode holder has an aperture defined by a thru-hole and a locating feature defined along an aperture axis. The thru-hole receives the cathode along the aperture axis in first and second alignment positions based on a rotational orientation of the positioning feature with respect to the locating feature. The first alignment position locates the cathode at a first axial position along the aperture axis. The second alignment position locates the cathode at a second axial position along the axial axis. A filament device has a filament clamp, a filament rod defining a filament axis, and a filament coupled to the filament rod. The filament clamp is in selective engagement with the filament rod to selectively position the filament along the filament axis within the blind hole.