| 摘要 |
PURPOSE:To prevent the fall of laser output at the initial stage of laser operation by changing the concentration of halogen gas, which forms excimer inside a laser discharge tube, during the time until impurity concentration reaches a saturation value since the start of laser oscillation. CONSTITUTION:A laser gas supply device 2 supplies the laser gas at the specified mixture ratio to a laser oscillator 1. After the supply of laser gas to the oscillator 1 is finished, the laser oscillation of the oscillator 1, the laser gas cleaning by a laser gas cleaning device 3, and the F2 gas supply by an F2 gas supply device 4 are started at the same time. The device 4 supplements the decrease amount of F2 gas accompanying the laser gas cleaning and the consumption amount of F2 gas consumed by the chemical change inside a discharge tube and the adsorption to the inner face of the discharge tube, and also supplies F2 gas to the oscillator 1 so that it may negate the fall of laser output by the concentration increase of the impurities excluding laser gas. |
