Layout of an Electron Ionization Ion Source

Mass Spectrometry, 2nd e L, DOI 10.1007/978-3-642-10711-5 5, Springer-Verlag Berlin Heidelberg 2011 

The beam of neutral gaseous analyte molecules enters the ionization chamber or ion volume, i.e., the actual region of ionization within the ion source block, in a line vertical to the paper plane and crosses the electron beam in the center. In order to reduce loss of ions by neutralizing collisions with the walls, the ions are pushed out immediately after generation by action of a low voltage applied to the repeller electrode [3,4]. They are then accelerated and focused towards the mass analyzer. Efficient ionization and ion extraction are of key importance for the construction of ion sources producing focusable ion currents in the nanoampere range [5]. 

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