Plasma Ion Source Mass Spectrometer

A mass spectrometer which uses plasma as an ion source, comprising an ion deflector lens,

• wherein the ion deflector lens comprises:
• an input side plate-like electrode having one aperture;
• an output side plate-like electrode having one aperture;
• and
• at least one tubular electrode disposed between the input side plate-like electrode and the output side plate-like electrode,
• wherein the input side plate-like electrode and the output side plate-like electrode face each other so that axes of the respective apertures are displaced from each other, and
• wherein the tubular electrode is of a point asymmetric shape, and arranged so that a center axis of the tubular electrode is closer to an axis of travel of ions upstream of the input side plate-like electrode than an axis of travel of ions downstream of the output side plate-like electrode.