A prototype surface ionization source coupled with a fixed-geometry extraction electrode system was commissioned on the Isotope Separator Accelerator (ISAC) ion source test stand at TRIUMF. The suitability of the ion source and extraction system for use in the ISAC facility was determined by a series of emittance measurements of the extracted beams. The test stand optics were successfully commissioned using the prototype ion source; emittance measurements of the mass-separated beams demonstrated that second- and third-order beam aberrations (introduced by the magnetic dipole mass separation) could be corrected by the use of multipole electrostatic optics elements. An upper limit of the root-mean-square-energy spread (2 eV) was deduced from the emittance measurements. Emittance measurements were performed at beam energies of 10–50 keV, as well as for ion masses ranging fromLi+toRb+,to demonstrate the feasibility of the prototype for a variety of beam energies and masses. ©1998 American Institute of Physics.