A multi-laminate wire mesh ionizer for a Cs sputter negative ion source

A new ventilated surface ionizer has been developed for a Cs sputter negative ion source after the cylindrical and spherical geometry ionizers, equipped with metal sheets, were successfully operated in a 860 A sputter source at BNU in 1990. The new ionizer is made up of multi-laminate nickel wiremesh and a spiral heater, and is shaped to a spherical-geometry with a 36 mm diameter. Low pressure cesium vapor will be diffused through the wiremesh to the extraction side of ionizer where, or before where, the neutral cesium can be ionized. The ionizer is capable of producing positive ion current in the millampere range and the negative ion currents are 250 μA of C and more than 150 μA of O and Si. Because of the reduction in erosion crater on the sample to approximately a diameter of 1 mm, the emittance is a lower compared to that of previous ionizers.