A versatile high intensity negative ion source

A new type of sputter negative ion source has been developed in which the sputter target and the surface ionizer are enclosed in a common chamber containing cesium vapor. Optimal neutral cesium coverage of the sputter target can be achieved resulting in efficient ionization and high intensities. Some typical negative ion currents are: 30 μA of 11B-, 300 μA of 12C-, 250 μA of 16O-, 4 μA of 27Al-, 200 μA of 28Si-, 150 μA of 58Ni-, 150 μA of 63Cu- and 200 μA of 197Au-. Emittance is relatively low, approx.= 2π mm x mrad (MeV)sup(1/2) for 70% of the total current, and sputter targets can be changed in 5-10 min. Since the source operates efficiently with samples of a few milligrams and yields 5-10 μA of BeO- ions from beryllium oxide and about 1 μA of 27Al- from aluminium oxide, it is likely to find application in accelerator mass spectrometry. (orig.)