Since almost 10 years we are using a 40-samples MC-SNICS Cs sputter source manufactured by NEC, Wisconsin. Over the years we implemented some minor and major modifications to improve the performance: (1)The pneumatic sample changer was completely replaced with a stepper motor drive, and in addition a motor-driven adjustment of the sample wheel's y-position was installed. These two modifications can be used to scan automatically the samples for centering the Cs-sputter spot to within 0.01 mm. (2)The improved adjustment opened the way to using sample wheels holding more than 40 sample positions, but keeping the original dimensions of the wheel. The use of more than 40 samples in a wheel gave rise to a new sample holder design. (3)We also implemented a computer-controlled regulation of the Cs-capillary heater power supply to keep the negative ion output rather constant by adjusting automatically the capillary's temperature. (4)Another modification was the replacement of the original conical ionizer with a spherical one following an idea of Weisser et al. [1], which increased the negative ion output by at least a factor of 2. To compensate for the enlargement of the diameter of the Cs-focus lens, we mounted a sample wheel shield, which essentially is a 5-mm diameter aperture at sample wheel's potential. (5)For rapid cool-down we have mounted an air lance blowing against the Cs oven. The presentation will discuss the mentioned modifications and their impact on the performance of AMS measurements with a variety of different ion species.
[1] D.C. Weisser, N.R. Lobanov, P.A. Hausladen, L.K. Fifield, H.J. Wallace, S.G. Tims, E.G. Apushkinsky, Novel matching lens and spherical ionizer for a cesium sputter ion source, Pramana – J.Phys. (Indian Academy of Sciences) 59/6 (2002) 997.
See more of Poster Session I
See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)