| 摘要 |
PROBLEM TO BE SOLVED: To prevent a situation that a spark discharge is generated frequently due to a change in a load impedance generated by a change in the state of the pressure, the flow rate, the concentration and the like of a laser gas and that a discharging electrode at a dust collection device is cut in an electrostatic dust removal apparatus for a discharge-excited excimer laser. SOLUTION: When the state of a mixed gas is changed, a signal output from any one sensor out of a pressure sensor 1, a halogen-gas concentration sensor 2 and a flow rate sensor 3 is changed. An output voltage (or current) control part 62 lowers or stops the maintenance voltage or current of a corona discharge inside a dust collection part 5 according to the output of one of the sensors 1 to 3. Thereby, it is possible to suppress a spark discharge from being generated continuously. On the other hand, when conductive dust particles come into the dust collection part 5, the signal of one of the sensors 1 to 3 which monitor the pressure, the flow rate and the concentration of the gas is not changed, an overcurrent protective circuit at the output voltage (or current) control part 62 acts, and the spark discharge is extinguished so as to be charged again. As a result, the operation of a dust collection device can be continued. |
