[en] Parametric studies were made on a hot cathode reflex discharge H^- Surface Ionization source with Transverse Extraction (SITEX) in both the pure hydrogen and the mixed hydrogen-cesium mode. Extraction current density, beam current, gas efficiency, extracted electron-to-H^- current ratio, heavy negative ion impurities, optics, and long pulse operation were investigated as a function of time, arc voltage, arc current, converter voltage, H₂ gas flow, cesium feed rate, and plasma generator geometries. Initial results of the research were an extracted H^- beam current density of 56 mA/cm² at 23 mA for 5 s pulses and, gas efficiency of 3%, theta_{perpendicular} (1/e) approx. 2 +- 1⁰, theta_parallel (1/e) approx. 1 +- 1⁰, at a beam energy of 25 keV. Negative heavy ion beam impurities were reduced to < 1% at low current densities. H^- ions are produced prinicpally by positive ion surface conversion using elemental cesium fractional monolayer coverage on a molybdenum converter substrate, which is biased negatively with respect to the anode