Abstract: A method is provided for determining the status of a gas mixture of a laser system including a gas discharge laser which generates an output beam and has a discharge chamber containing a gas mixture within which energy is supplied to the gas mixture by a power supply via application of a driving voltage to a discharge circuit. A master data set of an output parameter such as any of output beam energy, bandwidth, spectrum width, long axial beam profile, short axial beam profile, beam divergence, energy stability, energy efficiency, width of the discharge, temporal beam coherence, spatial beam coherence, spatial pulse width, amplified spontaneous emission and temporal pulse width versus an input parameter such as driving voltage is generated corresponding to an optimal gas mixture status, preferably after a new fill and typically at the factory, and alternatively following a new fill at the fab.