Mass spectrometer electric sector

Ion Optics of Magnetic/Electric-Sector Mass Spectrometers... 

In a sector instrument, which acts as a combined mass/velocity filter, this difference in forward velocity is used to effect a separation of normal and metastable mj" ions (see Chapter 24, Ion Optics of Magnetic/Electric-Sector Mass Spectrometers ). However, as discussed above, the velocity difference is of no consequence to the quadmpole instrument, which acts only as a mass filter, so the normal and metastable mj ions formed in the first field-free region (Figure 33.1) are not differentiated. 

Imaging SIMS. Steeds et al. (1999) included this technique in their study of the distribution of boron introduced into diamond, where it is a well-established dopant that controls the electrical conductivity. SIMS was performed with a field-emission liquid gallium ion source interfaced to a magnetic sector mass spectrometer capable of about 0.1 pm spatial resolution. 

A small fraction of the reactant ions collide with Cm molecules, and product ions scattered into the forward hemisphere in the laboratory frame are collected by the octapole. Product and unscattered reactant ions are mass selected by a double focusing electric and magnetic sector mass spectrometer, and detected by an on-axis Daly detector [16]. In the following we give only relative cross sections, due to uncertainties in the absolute pressure of Cm, the product collection efficiency, and the alkali-metal ion beam intensities in the scattering cell. 

A schematic representation of a double-focussing mass spectrometer is shown in Fig. 10.4. For historical reasons, this set-up is referred to as a reverse-geometry magnetic sector mass spectrometer, which means that the magnetic sector precedes the electric sector [1]. 

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