| 摘要 |
A closed-cycle gas scrubbing or purification system is described for noble gas and fluorine mixtures, such as are typically used in rare-gas fluoride (excimer) lasers. In a first reaction zone, the fluorine in the gas mixture is converted to titanium tetrafluoride vapor by reaction with titanium at a temperature above 150 degrees C., preferably at about 300 degrees C. The TiF4 vapor is then removed without passivating the titanium by condensing the TiF4 vapor in a separate condensation zone held at a temperature below the temperature of the first reaction zone, preferably at about room temperature. After condensing the TiF4 from the gas mixture, any silicon tetrafluoride in the mixture is chemically removed by contacting the gas mixture with an alkaline earth oxide (preferably either CaO or MgO) in a second reaction zone. Residual contaminants (i.e., contaminants other than SiF4) are removed from the gas mixture by contacting the gas mixture with a metal getter (preferably titanium of zirconium) at a temperature above 600 degrees C., preferably about 900 degrees C. or more. The hot metal gettering preferably is done in the second reaction zone by mixing or layering the metal getter with the alkaline earth oxide and heating the second reaction zone to a temperature above 600 degrees C. Fresh halogen gas is added to the purified rare-gas mixture before it goes back to the laser. Since SiF4 is specifically removed, it is acceptable to use industrial grade titanium to remove the fluorine and as a hot metal getter for residual contaminants. |
