Field fringing effects

Figure 3.2 Illustration of the relationship between electrical potential and electric field for parallel electrodes supplied by a5 V DC power supply. Lines ofequipotential are shown by the horizontal dashed lines and are perpendicular to the electric field, where the latter is shown by the vertically oriented lines (dot-dash). By convention the arrow on the electric field lines runs from higher to lower potential. This diagram is oversimplified because in practice the field lines do not run perpendicular to the inner surface of the electrodes near the left and right edges due to field fringing effects (see text for more details and also Figure 3.3).

We will lay particular emphasis in this chapter on factors that influence the design and evaluation of high performance EPR spectrometers. This means that we must take into account the vector properties of the electromagnetic field, the effect of diffraction fringes, and the assumption of paraxial beams. We will then discuss approximations to the complete treatment that are specially useful in spectrometer design. 

You may also assume that each of these structures can be approximated as an ideal parallel plate actuator, and that there is a uniform electrostatic load on each of them, as shown in Figure 3.10. You can also ignore the length of the beam taken up by the anchors in your calculations, and any fringing effects of the fields. The displacements would then be given by Cantilever beam ... 

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. 4.20). 

In a linear ion trap one of the most efficient ways to perform mass analysis is to eject ions radially. Hager [60] demonstrated that, by using fringe field effects, ions can also be mass-selectively ejected in the axial direction. There are several benefits for axial ejection (i) it does not require open slits in the quadrupole, (ii) the device can be operated either as a regular quadrupole or a LIT using one detector. A commercial hybrid mass spectrometer was developed based on a triple quadrupole platform where Q3 can be operated either in normal RF/DC mode or in the LIT ion trap mode (Fig. 1.24). 

Ghodrati M, Jury WA (1992) A field study of the effects of soil structure and irrigation method on preferential flow of pesticides in unsaturated soil. J Contam Hydrol 11 101-125 Gillham RW (1984) The effect of the capillary fringe on water-table response. J Hydrol 67 307-324... 

In order to get rid of the fringe field of the capacitor, one could work with a pulsed atomic beam and a pulsed voltage on the capacitor, using the scalar Aharonov-Bohm effect. If the voltage is applied when an atomic cloud is completely inside the field region and switched off before any atom has left this region, all atoms are in the electric field for the same amount of time. If the atoms spend a time r inside the capacitor when the field is applied,... 

LITs two modes for the mass selective ejection of ions are used either the ions are expelled axially using fringe field effects by applying AC voltages between the rods of the linear trap and the exit lens, or slots are hollowed out in two opposite rods and mass selective radial expulsion of ions is obtained by applying an appropriate AC voltage on these two rods. 

As shown in Figure 2.32, the ions are expelled axially using fringe field effects by applying AC voltages between the rods of the linear trap and the exit lens. 

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