The LANSCE accelerator facility operates with two independent ion injectors for H+ and H- particle beams. The H+ ion beam is formed using a duoplasmatron source followed by a 750 keV Cockroft-Walton accelerating column. Formation of an optimal plasma meniscus is an important feature for minimizing beam emittance, and maximizing beam brightness. A series of experiments were performed to find the optimal combination of extraction voltage and extracted current for the H+ beam. Measurements yielded the best ratio of beam perveance to Child-Langmuir perveance of 0.52 for maximizing beam brightness.