| 摘要 |
PURPOSE:To detect the leakage of gas as a medium for laser oscillation rapidly by mounting a housing vessel isolating a laser oscillating section and a detector detecting the gas in the housing vessel. CONSTITUTION:When a defect is generated in a discharge vessel 1, a gas supply system A or a gas discharge system B and gas for a laser-oscillation medium leaks into a housing vessel 20, air into which the gas mixes is introduced into a detector 23 through a pipe 21 by a motorized ventilating fan 35. When there is the gas for the laser oscillation medium, such as ArF, KrF, XeCl, XeF, etc. in the detector 23, alkali components, such as Na, K, etc. included in a ceramic pipe 31 are changed into cations, such as Na<+>, K<+>, etc. and flow into the cylindrical body 31 made of platinum mounted around a ceramic pipe 32. Consequently, currents mentioned above also flow through a resistor 41. The currents are amplified by an amplifier 42, and a discriminating circuit 43 decides a current value at that time to be larger than a fixed value, and transmits a signal. An alarm device 25 notifies the leakage of said gas while a valve 22 is closed, the leaking gas is interrupted in the housing vessel 20, and a diffusion to the outside of the housing vessel 20 of the gas is prevented. |
