Multipole Lenses

Abstract

In Chapters 4, 5, 7, a n d 8 the optical properties of axially symmetric fields were considered in detail. As we know, such fields have the property of stigmatic imaging in the first-order approximation, i.e., a point-to-point correspondence between the object and the image. This property is absolutely necessary for the purposes of electron microscopy. There are, however, many applications (e.g., particle accelerators, spectrometers, vacuum tubes, and, in general, even electron and ion probes) where stigmatic imaging is not required. Indeed, the role of beam optics for particle accelerators is just t o keep the beam together, analyze its parameters, and guide it to the experiments. No image has to be formed in this case.