| 摘要 |
PURPOSE:To suitably display the detection of the presence or absence of a malfunction in a piping system by judging whether the operation signal of a pressure sensor is generated or not in a predetermined time after the closure of a switching valve in a medium gas supply passage and the start of driving a gas exhaust pump. CONSTITUTION:A switching valve 26 is closed in a gas supply passage, a discharge pump 24 is started to be driven, and used deteriorated medium gas remaining in a laser discharge tube 11 and a piping system is gradually exhausted out of unit. In the step of gradually reducing gas pressure in the piping system, gas pressure value corresponding to a predetermined value, such as 15 sec. of a lapse time is monitored by a controller 7, and when the lapse time arrives at a predetermined value, if the gas pressure value of the piping system becomes predetermined value, i.e., 2 Torr, it is judged to be no malfunction to stop the pump 24 and then operate a normal procedure. If it does not becomes the predetermined pressure value, it is judged that there is a malfunction due to which outside air has entered the piping system or the system has a leakage to display an alarm on a display 6.
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