Space Charge in Cycloidal-Focusing Mass Spectrometers

In a curtate-cycloidal-focusing mass spectrometer, the first-order effect of space charge is not to impair the quality of the focus but to shift the focal point out of the plane of the resolving slit. For a given ion mass and ion current, the magnitude of the effect is about four times as large in a cycloidal-focusing instrument as in a 180° magnetic sector mass spectrometer operating in the same magnet.