Geometries of Double-Focusing Sector Instruments

The following passages present examples of particular double-focusing geometries that either have been milestones in instrument design [3,5] or still are incorporated in modem mass spectrometers. 

Note Typically, on magnetic sector mass spectrometers a spectrum is produced by varying the strength of the magnetic field to successively pass through ions of different m/z- This is termed magnetic field scan [73]. For scans linear in time, the scan rate is given in units of m/z s , e.g., 500 m/z s . For scans exponential in time, the scan rate is reported in units of s per decade, e.g., 10 s/decade means 10 s from m/z 30 to 300 or from m/z 100 to 1000. 

Later EB instrument models are often constructed to be used in combination with an (optional) array detector, e.g., the JEOL HX-110 (EB), the Thermo Finni-gan MAT 900 (EB), and the Micromass Autospec (EBE) instruments can be equipped in that way. The array detector is then located at the focus plane of the magnet, in contrast to the Mattauch-Herzog design it only covers a comparatively small m/z range simultaneously. 

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Figure 2 Geometries of double-focusing sector instrument Nier-Johnson (EB) geometry and reversed geometry.

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