An automatic F₂ laser gas control, for a modular high repetition rate ultraviolet gas discharge laser. The laser gas control includes techniques, monitors, and processor for monitoring the F₂ consumption rates through the operating life of the laser system. These consumption rates are used by a processor programmed with an algorithm to determine F₂ injections needed to maintain laser beam quality within a delivery range. Preferred embodiments include F₂ controls for a two-chamber MOPA laser system.