JMSSJ On-line, Vol. 51 (2003) No. 5, pp. 563-565
Optimization of Electron Impact Cluster Ion Source and Ammonia Cluster Generation
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    Yoko KAWAI a), Satoru YAMAGUCHI a), Yoshiki OKADA *a), and Kazuo TAKEUCHI a)

    *a)RIKEN (The Institute of Physical and Chemical Research)(Hirosawa, Wako-shi, Saitama 351-0198, Japan)
An electron impact (EI) ion source was developed for cluster ion generation. Ammonia was used as a model gas to optimize various conditions of the EI source for cluster ion generation. Electrons emitted from tungsten filaments were accelerated through slits into the region where a nozzle for supersonic expansion was placed. We examined the effects on cluster intensities of the slits' length, distance d between the head of the nozzle and ionization point, and aperture size of the nozzle. It was found that the longer slits 15 mm could provide greater cluster ion intensities than the shorter ones 5 mm. The distance d was confirmed to be critical on the cluster intensities. The larger aperture ø50 μm was found to be favorable for cluster generation than the smaller one, ø30 μm, and the effect of d was attenuated with the larger aperture.
Key words: Electron impact, Cluster formation, Cluster ion, Ammonia cluster
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