An assembly present in an ion source for supporting an arc chamber upon a base plate includes a first arc support plate, a first screw, and a second screw. The first screw passes through a smooth through-hole in an arm of the first arc support plate and extends into a bore in the base plate. The second (or adjustable) screw passes through a threaded through-hole in an arm of the first arc support plate and engages an upper surface of the base plate itself, and can be used to change the altitude and angle of the first arc support plate relative to the base plate. This adjustment ability improves the beam quality of the ion source.