To provide a high quality alarm system relating to discharge laser and integrated circuit lithography, as informing technique for alarming whether an intelligent internal monitor a preliminarily selectable quality standard, or the quality of a beam is suitable for manufacturing, to a user of laser.

The discharge laser is provided with a programmable controller of an informing signal to an operator when beam quality is suitable for manufacturing an integrated circuit. The controller is programmed to indicate an out-of- control condition when one or more quality parameters exhibit certain specified non-random behavior such as two out of three quality measurement deviating by more than 4 standard deviations and for three out of four quality measurements deviating by more three standard deviations. The program detects poor quality by looking for 'runs' of bad quality data, and produces false indication of system out of control, on the average, no more than once each two months.