| 摘要 |
PURPOSE:To securely operate the captioned ion source with higher luminance by providing an ionization chamber having an emitter tip therein, a cooling means for cooling the wall of the ionization chamber and the emitter tip, and a gas introducing tube having a second cooling means provided therearound and connected to the ionization chamber via a cooling trap. CONSTITUTION:When the gas in question is precooled near a cooling medium reservoir 19, impurities contained in the gas, particularly water, are adsorbed onto the tube wall of a gas introducing tube 18 whereby purity of the gas is improved. Moreover, an ionization chamber 10 has its outer wall in close contact with the cooling surface of a cooler 17 and is kept at lower temperature over the whole thereof, and thereby the impurities in the gas are adsorbed also onto a cooling trap 14 or onto the inner wall surface of the ionization chamber 10 to further improve the purity of the gas. The ion source does not allow gas, etc., included in the ionization chamber 10, an emitter tip 16, and the interior of the ionization chamber 12 to be raised in their temperature, although allowing increase in quantities thereof to enhance luminance and thus a large ionic current corresponding to the large amount of the introduced gas is available. |
