| 摘要 |
PURPOSE:To prevent the insulation breakdown of parts of the gas exhaust side by a method wherein the third electrode is provided in the flow downstream of the cathode of the laser gas, then a discharge is performed between it and the cathode, and ions carried over the cathode are returned to the cathode. CONSTITUTION:The third electrode is formed by using a metallic exhaust pipe 14 on a part of a gas exhaust pipe 11, then the second DC power source 15 and a stable resistor 16 are inserted in series between the cathode 4 and the electrode 14, thus the low resistor 16 is selected to a sufficient high value, and, with the electrode 14 as the anode, a very small DC discharge is performed through the exhaust pipe 10. When a main pulse discharge is performed between the first anode 3 and the cathode, a part of ion particles in the plasma passes through the cathode 4 and flows out in the direction of a vacuum pump 12 through the pipes 10 and 11. Then, the ions having posiitive charges are repelled at the electrode 14 and returned to the cathode 4, accordingly being not electrified to the exhaust pipe 11. The ions are neutralized by the weak discharge between the electrodes 4 and 14, and not made to flow to the exhaust port 13. Therefore, low cost materials can be used to the exhaust side from the electrode 14, and the insulation breakdown does not generate, accordingly an operation which is stable for a long time is enabled. |
