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 n egative ion source after the cylindrical and spherical geometry ionize rs, 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-lam inate nickel wiremesh and a spiral heater, and is shaped to a spherica l-geometry with a 36 mm diameter. Low pressure cesium vapor will be di ffused through the wiremesh to the extraction side of ionizer where, o r before where, the neutral cesium can be ionized. The ionizer is capa ble of producing positive ion current in the millampere range and the negative ion currents are 250 mu A of C and more than 150 mu A of O an d Si. Because of the reduction in erosion crater on the sample to appr oximately a diameter of 1 mm, the emittance is a lower compared to tha t of previous ionizers.