No single volume has been entirely devoted to the properties of magnetic lenses, so far as I am aware, although of course all the numerous textbooks on electron optics devote space to them. The absence of such a volume, bringing together in formation about the theory and practical design of these lenses, is surprising, for their introduction some fifty years ago has created an entirely new family of commercial instruments, ranging from the now traditional transmission electron microscope, through the reflection and transmission scanning microscopes, to co lumns for micromachining and microlithography, not to mention the host of experi mental devices not available commercially. It therefore seemed useful to prepare an account of the various aspects of mag netic lens studies. These divide naturally into the five chapters of this book: the theoretical background, in which the optical behaviour is described and formu lae given for the various aberration coefficients; numerical methods for calculat ing the field distribution and trajectory tracing; extensive discussion of the paraxial optical properties and aberration coefficients of practical lenses, il lustrated with curves from which numerical information can be obtained; a comple mentary account of the practical, engineering aspects of lens design, including permanent magnet lenses and the various types of superconducting lenses; and final ly, an up-to-date survey of several kinds of highly unconventional magnetic lens, which may well change the appearance of future electron optical instruments very considerably after they cease to be unconventional.

Klappentext

With contributions by numerous experts

Inhalt

1. Magnetic Lens Theory.- 1.1 Derivation of the Equations of Motion of Electrons in Rotationally Symmetric Magnetic Fields.- 1.2 Paraxial Properties.- 1.3 Methods of Calculating Aberration Coefficients.- 1.4 Aberration Coefficients.- 1.5 Parasitic Aberrations.- References.- 2. Magnetic Field Calculation and the Determination of Electron Trajectories.- 2.1 Basic Concepts.- 2.2 Methods of Discretization.- 2.3 Solution of the Discretized Equations.- 2.4 Differentiation and Interpolation in Mesh Grids.- 2.5 Analytical Field Calculation.- 2.6 Field Calculation in Systems Without Rotational Symmetry.- 2.7 The Calculation of Electron Trajectories.- 2.8 Concluding Remarks.- References.- 3. Properties of Electron Lenses.- 3.1 Concepts and Definitions.- 3.2 Field Distribution in Unsaturated Lenses.- 3.3 Analytical Field Models.- 3.4 Paraxial Properties.- 3.5 Third-Order Aberrations.- References.- 4. Practical Lens Design.- 4.1 Introduction.- 4.2 General Rules for the Electron Optical Design of the Magnetic Lens.- 4.3 Design of the Magnetic Circuit.- 4.4 Other Aspects of Magnetic Lens Design.- 4.5 Measures for Reducing the Sensitivity of the Magnetic Electron Lens to Environmental Disturbances.- 4.6 Permanent Magnet Lenses.- 4.7 Superconducting Electron Lenses.- References.- 5. Unconventional Lens Design.- 5.1 Introduction.- 5.2 Boiling-Water Cooling Systems.- 5.3 Miniature Rotation-Free Magnetic Electron Lenses.- 5.4 Iron-Free or Partly Shrouded Magnetic Lenses.- 5.5 Iron-Shrouded Pancake Lenses.- 5.6 Improved Image Viewing Systems.- 5.7 Correction of Spiral Distortion.- 5.8 Concluding Remarks.- References.- Appendix A Some Earlier Sets of Curves Representing Lens Properties.- Appendix B Bibliography of Publications on Magnetic Electron Lens Properties.