Mass spectrometers fixed collector

An ion beam causes secondary electrons to be ejected from a metal surface. These secondaries can be measured as an electric current directly through a Faraday cup or indirectly after amplification, as with an electron multiplier or a scintillation device. These ion collectors are located at a fixed point in a mass spectrometer, and all ions are focused on that point — hence the name, point ion collector. In all cases, the resultant flow of an electric current is used to drive some form of recorder or is passed to an information storage device (data system). 

A Nier type mass spectrometer has a fixed radius of curvature of S cm and a magnetic field of 3000 G 1 G = 10" T. At what accelerating voltage will a Na " ion be brought to focus at the ion collector ... 

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