Superconducting Electron-Optic Devices

ISBN-13: 9781468422016 / Angielski / Miękka / 2012 / 140 str.

I. Dietrich

Opis

* Electron optics involves the influence of electric and magnetic fields on electron beams. In those electron optical instruments utilizing magnetic fields, a replacement of the conventional, i.e .. nonsuperconducting, electron optical parts, is worth considering if the outstanding magnetic properties of superconductors can improve the systems. However, the use of superconductors demands complicated cryogenic techniques and this, of course, dampens enthusiasm. There are fields, however, where there are extreme requirements on the optical systems, namely, electron microscopy and high-energy physics. The great advantage of the combination of electron optics and superconductivity in these domains has been demonstrated in recent experiments. This monograph is mainly concerned with electron micros- copy. Superconductivity in high-energy electron optics is treated only briefly, in Appendix A, since the author is little acquainted with the details of the projects. Furthermore, the number of experiments as yet carried out is small. In Appendix B, electron microscope studies of basic superconductor phenomena are reviewed. This material is included, even though it is only slightly connected with the main topic of the book, since a breakthrough in this field may be possible by the application of superconducting lenses.

Spis treści

1 Historical Survey.- 2 Basic Principles of Electron Optics.- 2.1. Rotationally Symmetric Lenses in the Bell-Shaped Field Approximation.- 2.2. Rotationally Symmetric Lenses with Arbitrary Field Distribution.- 2.3. Aberrations Resulting from Misalignment.- 2.4. Multipole Fields for Beam Correction.- 2.5. Image Contrast.- 2.6. Further Sources of Error.- 2.7. Fixed Beam and Scanning Mode.- 3 Superconducting Devices in Electron Microscopy.- 3.1. Advantages of Superconducting Devices.- 3.1.1. Improvements Resulting from the Use of Superconducting Materials.- 3.1.2. Improvements Resulting from the Liquid Helium Temperature in the Optical Devices.- 3.1.3. Economic Aspects.- 3.2. Technical Problems.- 3.2.1. Construction of Cryostats.- 3.2.2. Superconducting Materials.- 3.2.3. Normal Materials.- 4 Lens Design and Testing.- 4.1. Lens Design and Field Distribution.- 4.1.1. General Remarks.- 4.1.2. Coil Lens.- 4.1.3. Ring Lens.- 4.1.4. Iron Circuit Lens.- 4.1.5. Shielding Lens.- 4.1.6. Advantages and Drawbacks of the Different Lens Types.- 4.2. Correction Systems for Superconducting Objective Lenses.- 4.3. Testing of Objective Lenses.- 4.3.1. Testing Objective Lenses with Simulation Devices.- 4.3.2. Testing in the Microscope.- 5 Systems with Superconducting Lenses.- 5.1. Tested Systems.- 5.2. Projected Systems.- 6 Other Superconducting Elements for Electron Microscopy.- 6.1. Superconducting High-Voltage Beam Generator.- 6.2. Magnetic Dipoles.- 7 Proposed Superconducting 3-MV Microscope.- 7.1. Accelerator.- 7.2. Spectrometer.- 7.3. Microscope Column.- 7.4. Further Improvements of the System.- Appendixes.- A. Superconducting Electron Optical Systems for High-Energy Physics.- A.1. General Remarks.- A.2. Magnet Designs.- B. Application of Electron Microscopy to Basic Research on Superconductivity.- B.1. Imaging by the Decoration Method.- B.2. Imaging by Electron Shadow Microscopy.- B.3. Imaging by an Electron Mirror Microscope.- B.4. Imaging by Lorentz Microscopy.- B.5. Imaging by a Vortex Electron Microscope.- References.