5:51 PM - 5:54 PM
[SGC51-P03] High sensitive noble gas mass spectrometer equipped with a Giese-type ion source
3-min talk in an oral session
Keywords:Noble gas, Mass spectrometer, Quadrupole lens, Ion source
The Giese-type electron ionization (EI) ion source is equipped with two electrostatic quadrupole lenses . This source has been reported to have up to two orders of magnitude higher sensitivity than conventional Nier-type EI source because of the absence of a beam defining slit to collimate the ion beam and thus high transmission . We designed a Giese-type source to have an adequate resolution to separate 3He+ from HD+ and H3+, to have the source housing volume as small as possible, and to be bankable at up to 300℃ to reduce outgas from the source materials. The ion and electron optics were based on a calculation by Lu and Carr  and refined using SIMION-3D software . Prior to the installation on the mass spectrometer, the ion beam profile emitted from the source was monitored by a microchannel plate and phosphor screen to optimize the configuration of the quadrupole lens.
A sufficient mass resolution over 500 essential for 3He/4He analysis has been achieved with an improved sensitivity approximately three times higher than the previous condition. The amount of helium required to obtain a precision with 3He/4He ratio is two orders of magnitude smaller than that with the condition installed by the manufacture. However, total ion transmission is estimated to be about 30%, suggesting further refinement of the source condition is required to obtain the maximum sensitivity.
References:  H. Sumino et al., J. Mass Spectrom. Soc. Jpn., 49, 61-68 (2001).  C.F. Giese, Rev. Sci. Instrum., 30, 260-261 (1959).  E.T. Kinzer and H. Carr, Rev. Sci. Instrum., 30, 1132 (1959).  C.-S. Lu and H.E Carr, Rev. Sci. Instrum., 33, 823-824 (1962).  D.A. Dahl, Int. J. Mass Spectrom., 200, 3-25 (2000).