抄録
When an excimer laser operates continuously for long time, gaseous impurities are produced by the excitation discharge. The gaseous impurities reduce a laser output power.
In this paper, we propose to apply the technique of removal of gaseous impurities using corona discharge for excimer laser gas. This technique utilizes electron attachment characteristic of gaseous impurities. The removal of gaseous impurities of chromium fluoride and carbon tetrafluoride (CF4) Were investigated. In the experiment of chromium fluoride, a corona discharge tube and a discharge chamber for the measurement of the emission spectrum from a sample gas were set in a closed gas looP. On the observation of the emission spectrum, it was found that chromium was decreased by passing through the corona discharge tube. The fact shows that chromium fluoride is removed by corona discharge. In the experiment of CF4, the concentration of CF4 was measured by the method of the absorption spectrophotometry. It was found that CF4 was decreased by passing through the corona discharge tube. As the corona discharge current increased and the gas flow rate decreased, the removal rate of CF4 increased. Approximately 96% of CF4 was removed in this experiment.
