Exposition

Ion source adjustable slit

Exhibit no. 381

The ion beam width in a mass spectrometer can be defined by means of mechanical slits. These slits may be of fixed dimensions or adjustable from outside the vacuum chamber.

The mechanism usually includes a micrometer screw, feedthrough through the vacuum wall, and numerous levers, pivots, springs and sliding components within the vacuum system. The adjustable slits allow the resolving power of the instrument to be tuned. Narrowing the slits permits high-resolution measurements, but at the cost of lower ion transmission (and therefore lower sensitivity).

The exhibit is an adjustable object slit from the ZAB-EQ sector mass spectrometer manufactured by VG Analytical LTD. in 1986. It was located in the ion source housing and positioned 100 mm away from the ion source to reduce contamination of the slit blades, particularly in FAB and CI modes of operation.

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