Technique for Simulating and Evaluating Aero-optical Effects in Optical Systems

2004 ◽  
Author(s):  
James Trolinger ◽  
William Rose
Keyword(s):  
Optical Systems ◽  
Optical Effects

scholarly journals Stationary electron swarms in electromagnetic fields

1945 ◽  
Vol 183 (995) ◽  
pp. 436-453 ◽  
Keyword(s):  
Magnetic Fields ◽  
Difficult Problem ◽  
Optical Systems ◽  
Axially Symmetric ◽  
Free Electrons ◽  
Uniform Distributions ◽  
Optical Effects ◽  
Long Time ◽  
Electron Clouds ◽  
The Magnetic Field

Electron clouds rotating in axially symmetric magnetic fields have been known for a long time, but the agreement between theory and experiment is still very unsatisfactory. The discrepancy appears to be due to the interaction of electrons. Before approaching this difficult problem it is desirable to possess a more complete theory of stationary swarms without interaction. In the present paper the distribution density is calculated on the basis of classical statistical mechanics. It is shown that electrons injected at any point with very small initial velocities will distribute themselves with a density inversely proportional to the distance from the axis, in a certain annular space. Only the limits of this space, not the distribution inside it, will be dependent on the electric or magnetic fields. The uniform or nearly uniform distributions calculated by previous authors are singular solutions, inconsistent with any degree of statistical disorder. Other laws of density distribution can be realized by simultaneous injection of electrons at several points. These offer a possibility to realize dispersing electron lenses and corrected electron optical systems. It is shown that the ring current produced by the rotating electron cloud can reduce the magnetic field at the axis very considerably in devices of practicable dimensions. It appears also possible to produce clouds of free electrons with densities sufficient for observable optical effects.

Atomic Resolution in Crystal Aperture Stem

1990 ◽  
Vol 48 (1) ◽  
pp. 236-237
Author(s):  
J T Fourie
Keyword(s):  
Optical System ◽  
Spherical Aberration ◽  
Three Dimensional ◽  
Transmission Function ◽  
Optical Systems ◽  
Bragg Angle ◽  
Electron Optical System ◽  
Intimate Contact ◽  
Diffraction Effects ◽  
Design Aspect

The attempts at improvement of electron optical systems to date, have largely been directed towards the design aspect of magnetic lenses and towards the establishment of ideal lens combinations. In the present work the emphasis has been placed on the utilization of a unique three-dimensional crystal objective aperture within a standard electron optical system with the aim to reduce the spherical aberration without introducing diffraction effects. A brief summary of this work together with a description of results obtained recently, will be given.The concept of utilizing a crystal as aperture in an electron optical system was introduced by Fourie who employed a {111} crystal foil as a collector aperture, by mounting the sample directly on top of the foil and in intimate contact with the foil. In the present work the sample was mounted on the bottom of the foil so that the crystal would function as an objective or probe forming aperture. The transmission function of such a crystal aperture depends on the thickness, t, and the orientation of the foil. The expression for calculating the transmission function was derived by Hashimoto, Howie and Whelan on the basis of the electron equivalent of the Borrmann anomalous absorption effect in crystals. In Fig. 1 the functions for a g220 diffraction vector and t = 0.53 and 1.0 μm are shown. Here n= Θ‒ΘB, where Θ is the angle between the incident ray and the (hkl) planes, and ΘB is the Bragg angle.

SPATIAL AND TEMPORAL INSTABILITIES IN PASSIVE OPTICAL SYSTEMS

1988 ◽  
Vol 49 (C2) ◽  
pp. C2-343-C2-348
Author(s):  
L. A. LUGIATO ◽  
C. OLDANO ◽  
Kaige WANG ◽  
L. SANTIRANA ◽  
L. M. NARDUCCI ◽  
...  
Keyword(s):  
Optical Systems
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