Neutral and ionized alkaline metal bombardment type heavy negative-ion source (NIABNIS)

Abstract

A new type of high current, heavy negative-ion source has been developed in which simultaneous bombardment of both neutral and ionized alkaline metal particles on a sputter cone is utilized for overcoming the disadvantages of the universal negative ion source and the Aarhus negative ion source. To supply a sufficient amount of neutral and ionized cesium particles onto the sputtering target surface, a plasma cesium ion source is used for the primary cesium ion source, and the distance between the extraction aperture of the cesium ion beam and the sputtering target is minimized. This results in a compact body and high yields of negative ion currents. Two experimental apparatus are used: a prototype source for mainly investigating the operating principle and a high current negative ion production source with a target cooling system. The neutral cesium particle bombardment was found to be effective in increasing the negative ion production efficiency. The target surface temperature also had a great influence on this efficiency. Negative ion production experiments of group III, IV and V elements were mainly made. 320 μA of the C − ion current and 3 μA of the 11B − ion current were obtained. Negative ion currents obtained to-date are also given for various targets.