| 摘要 |
PURPOSE:To adsorb and eliminate impurity molecules and atoms except ionized gas by positioning an annular Ti evaporation source enclosing an emitter positioned within an ionization chamber, and heating the Ti evaporation source to generate Ti gas. CONSTITUTION:An ionization chamber 11 is kept to the temperature 10 deg.K to dozens of 10 deg.K by means of a cooler 12. A Ti evaporation source 17 in which a spiral member of Ti is formed to an annular shape is positioned to enclose an emitter above an emitter chip. Before operating, the ionization chamber 11 is cooled to said temperature and the evaporation source 17 is heated. Activated Ti gas is discharged from the evaporation source 17, and the Ti gas adheres to the inner wall of an ionization chamber wall 11a to adsorb and eliminate the impurities within the chamber 11. After such a preliminary operation, ionized gas is introduced to generate an ion beam. Whereby, since the chamber 11 is kept to the state that the impurities are strikingly reduced, the brightness of the ion beam is increased and the stability of operation is obtained.
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