Innovations in Sector Instruments

To further improve the performance of sector instruments in terms of scan speed, resolving power, transmission, and mass range, the construction, in particular that of the magnet, needs some additional refining. 

Another problem is due to fringing fields. To reduce these defocusing effects at the entrance and exit of the field, the pole pieces of the yoke of the electromagnet generally have specially shaped edges (Fig. 4.16). 

In order to extend the mass range one either has to increase the field strength or the radius of the magnet. However, there are limitations of the field strength with nonsuperconducting magnets at about 2.4 T. Instead of simply enlarging the ra- 

The JEOL JMS-700 double-focusing magnetic sector instrument for a scheme of this instrument design cf. Fig. 4.24. 

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