Electromagnetic sector fields

Double focusing sector field instruments incorporate a combination of electromagnetic fields (B) and electric fields (E). 

Figure Bl.6.3 Electron energy analysers that use magnetic fields (a) the trochoidal analyser employing an electromagnet, (b) the Wien filter and (c) the sector magnet analyser. Trajectories for electrons of different energies are shown.

Through the use of sequential electric (electrostatic) and magnetic fields (sectors) and various correcting lenses, the ion beam leaving the ion source can be adjusted so that it arrives at the collector in focus and with a rectangular cross-section aligned with the collector slits. For the use of crossed electromagnetic fields. Chapter 25 ( Quadrupole Ion Optics ) should be consulted. 

The second Higgs field acts in such a way that if the vacuum expectation value is zero, ( ) = 0, then the symmetry breaking mechanism effectively collapses to the Higgs mechanism of the standard SU(2) x U(l) electroweak theory. The result is a vector electromagnetic gauge theory 0(3)/> and a broken chiral SU(2) weak interaction theory. The mass of the vector boson sector is in the A(3) boson plus the W and Z° particles. 

The first research instruments were based on the ungainly magnetic sector mass spectrometers that used very large permanent magnets to establish the electromagnetic field and had very slow response times. The accelerated ions of different masses were detected at different impact points on the detector plate and mass ratios were measured (Fig. 15.2). 

An important application field for stainless steel fibers is the textile sector, in which 0., i to 6% of these fibers are incorporated to endow carpets, protective clothing etc. with an antistatic finish. A further application is protection against electromagnetic pulses, interference and charging. Tungsten fibers with a diameter of 12 pm are used for boron or SiC deposition and as light bulb filaments. Furthermore, metal fibers are used in the filtration of polymer melts and corrosive liquids, as well as for electrodes with high surface areas. 

Magnetic sector instruments are further distinguished by their method of sample introduction - how the sample is put into the electromagnetic field. Many instruments today use a plasma, identical to that in optical ICP spectroscopy (ICP-MS). In the mass spec, the plasma is used to ionize the atoms. Although the plasma emits the characteristic spectra used in ICP-OES, this visible light output is not used by the mass spectrometer. Figure 4.25 shows the ICP-MS in the Laboratory for Archaeological Chemistry at the University of Wisconsin-Madison. 

An essential part of the double-focusing analyzer is a magnetic sector, an electromagnet with a well-defined geometry. Ions are ejected from an ion source by the action of an acceleration field. Their potential energy is fully transformed in kinetic energy... 

Figure 16.4. Mass analysis in a sector magnetic field. Poles of the electromagnet are located above and below the plane of the page. The magnetic field H points perpendicularly out of the plane of the page. Note that the two slits and the apex of the sector are colinear.

A sector mass-spectrometer is built to scan to mje = 500 with the maximum field of the electromagnet at 6000 gauss and an accelerating voltage of 3000 V. To examine the molecular ion of a compound of molecular mass 850, what modification in the accelerating-voltage power-supply is required ... 

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