Negative-ion production of reactive elements from compound gases in the RF plasma-sputter-type heavy negative-ion source

To obtain negative ions of chemically reactive elements, a material gas and a stainless-steel sputtering target are used instead of an oxide or fluoride sputtering target to prevent charging trouble in the RF plasma-sputter-type heavy negative-ion source which was developed for obtaining intense negative-ion beam with a high-current in mA class. The operational characteristics of the negative-ion source with a feeding of O₂ or SF₆ gas as an ionized material together with Xe gas is presented. By gradually increasing the Cs supply, O^- or F^- become to be dominant in the extracted beam. Then, high-current negative ions of mA class such as 4.6 mA for O^- 4.3 mA for F^- were extracted in a DC-mode operation. Even in the source with a material gas, the surface production of negative ions was found to be the dominant mechanism, because that gas particles introduced and absorbed on the target surface were negatively ionized by sputtering. In a similar manner with nitrogen gas and carbon target, a compound molecular negative ion of CN was obtained with a considerably large amount