= Surface ionization detector
A <surface ionization detector> detects a neutral <atomic beam> by converting incident <chemical atoms> into <ions> on a hot surface. For suitable <alkali metals>, a heated <tungsten> surface can favor loss of an <electron>: the competing surface <work function> and atomic <ionization energy> make the efficiency strongly dependent on species, surface condition and <temperature>. An <electric field> then collects the resulting <ions>, producing an <electric current> or a count after amplification. A response therefore requires an efficiency <measurement calibration>; it is not automatically equal to the incident <particle flux>.
A 2002 imaging experiment used a tungsten-coated heated ribbon followed by a <microchannel plate detector> and a <phosphor> screen. It recorded where the arriving neutral <chemical atoms> struck, rather than just their total rate. The reported approximately $20\,\mu\mathrm m$ spatial resolution and roughly $50\%$ detection efficiency belong to that apparatus and its conditions, rather than to every <surface ionization detector>.<Two-Dimensional Imaging of Neutral Alkali Atom Samples Using Surface Ionization by Katharina Gillen-Christandl and others>[abstract: hot ribbon, ion acceleration, spatial resolution and efficiency]{ref}
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