Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references and index.

Detectors for Electron Microscopy have traditionally used a scintillator to generate photons from fast electrons, which are then detected by a sensor. However, in recent years direct detection has become an area of interest due to the potential improvements to detector performance. In this thesis various aspects of direct detection are presented. I will begin with simulations of direct detectors based on Joy’s model of straight trajectories between Rutherford scattering events, where signal is generated by inelastic scattering events. The effects of microscope operating voltage, detector thickness, a surface electrically dead layer and diode depth on detector performance are presented. A prototype detector was developed using the DUOS sensor, two thicknesses of the sensor were produced a 50μm thick detector and a 20μm thick detector. EBSD results are presented which show how the use of a reactive ion etch to reduce the dead layer thickness of a mechanically thinned sensor improve the detection efficiency of a sensor allowing EBSD work to be carried out at operating voltages as low as 5keV. The MTF and DQE of both thicknesses of DUOS sensor are measured at 80kV and 200kV, which show that there is little difference between the two thicknesses at 80kV, but at 200kV the thinner detector shows an improved MTF. The results are then and compared with the equivalent simulated detectors. I show how the high frame rate of a detector and rigid and non-rigid registration can be used to improve image quality, resolving the {331} lattice spacing which is not visible with a simple summation of frames. Detectors using gallium nitride rather than silicon as the base semiconductor are simulated. The MTF at the Nyquist frequency for a GaN detector is double that of a Si detector at an operating voltages of 80kV due to the smaller interaction volume of an electron in GaN. However, at higher voltages the improvement is much smaller as most electrons pass through the detector.

by Kwan Wai Wing Eric. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references. / ABSTRACT / ACKNOWLEDGMENT / LIST OF FIGURES / LIST OF TABLES / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Background --- p.1-1 / Chapter 1.2 --- E-Beam testing and test generation algorithm --- p.1-2 / Chapter 1.3 --- Motivation of this research --- p.1-4 / Chapter 1.4 --- Out-of-kilter Algorithm --- p.1-6 / Chapter 1.5 --- Outline of the remaining chapter --- p.1-7 / Chapter Chapter 2 --- Electron Beam Testing / Chapter 2.1 --- Background and Theory --- p.2-1 / Chapter 2.2 --- Principles and Instrumentation --- p.2-4 / Chapter 2.3 --- Implication of internal IC testing --- p.2-6 / Chapter 2.4 --- Advantage of Electron Beam Testing --- p.2-7 / Chapter Chapter 3 --- An exhaustive method to minimize test sets / Chapter 3.1 --- Basic Principles --- p.3-1 / Chapter 3.1.1 --- Controllability and Observability --- p.3-1 / Chapter 3.1.2 --- Single Stuck at Fault Model --- p.3-2 / Chapter 3.2 --- Fault Dictionary --- p.3-4 / Chapter 3.2.1 --- Input Format --- p.3-4 / Chapter 3.2.2 --- Critical Path Generation --- p.3-6 / Chapter 3.2.3 --- Probe point insertion --- p.3-8 / Chapter 3.2.4 --- Formation of Fault Dictionary --- p.3-9 / Chapter Chapter 4 --- Mathematical Model - Out-of-kilter algorithm / Chapter 4.1 --- Network Model --- p.4-1 / Chapter 4.2 --- Linear programming model --- p.4-3 / Chapter 4.3 --- Kilter states --- p.4-5 / Chapter 4.4 --- Flow change --- p.4-7 / Chapter 4.5 --- Potential change --- p.4-9 / Chapter 4.6 --- Summary and Conclusion --- p.4-10 / Chapter Chapter 5 --- Apply Mathematical Method to minimize test sets / Chapter 5.1 --- Implementation of OKA to the Fault Dictionary --- p.5-1 / Chapter 5.2 --- Minimize test set and optimize internal probings / probe points --- p.5-5 / Chapter 5.2.1 --- Minimize the number of test vectors --- p.5-5 / Chapter 5.2.2 --- Find the optimum number of internal probings --- p.5-8 / Chapter 5.2.3 --- Find the optimum number of internal probe points --- p.5-11 / Chapter 5.3 --- Fixed number of internal probings/probe points --- p.5-12 / Chapter 5.4 --- True minimum test set and optimum probing/ probe point --- p.5-14 / Chapter Chapter 6 --- Implementation and work examples / Chapter 6.1 --- Generation of Fault Dictionary --- p.6-1 / Chapter 6.2 --- Finding the minimum test set without internal probe point --- p.6-5 / Chapter 6.3.1 --- Finding the minimum test set with optimum internal probing --- p.6-10 / Chapter 6.3.2 --- Finding the minimum test set with optimum internal probe point --- p.6-24 / Chapter 6.4 --- Finding the minimum test set by fixing the number of internal probings at 2 --- p.6-26 / Chapter 6.5 --- Program Description --- p.6-35 / Chapter Chapter 7 --- Realistic approach to find the minimum solution / Chapter 7.1 --- Problem arising in exhaustive method --- p.7-1 / Chapter 7.2 --- Improvement work on existing test generation algorithm --- p.7-2 / Chapter 7.3 --- Reduce the search set --- p.7-5 / Chapter 7.3.1 --- Making the Fault Dictionary from existing test generation algorithm --- p.7-5 / Chapter 7.3.2 --- Making the Fault Dictionary by random generation --- p.7-9 / Chapter Chapter 8 --- Conclusions / Chapter 8.1 --- Summary of Results --- p.8-1 / Chapter 8.2 --- Further Research --- p.8-5 / REFERENCES --- p.R-1 / Chapter Appendix A --- Fault Dictionary of circuit SC1 --- p.A-1 / Chapter Appendix B --- Fault Dictionary of circuit SC7 --- p.B-1 / Chapter Appendix C --- Simple Circuits Layout --- p.C-1

Ultrafast electron diffraction (UED) is a method of directly imaging system dynamics at the atomic scale with picosecond time resolution. In this thesis I present theoretical analyses of the experimental processes, and construct models in order to better understand UED experiments and to guide future refinements. In particular, I derive a model of electron bunch propagation and a model of electron bunch diffraction, where both models take into account all bunch parameters. To analyse the propagation of electron bunches, I present a mean-field analytic Gaussian (AG) model. I derive a system of ordinary differential equations that are solved quickly and easily to give the bunch dynamics. The AG model is compared to N -body numerical simulations of initially Gaussian bunches, and I demonstrate excellent agreement between the two result sets. I also present a comparison of the AG model with numerical simulations of quasi-Gaussian and non-Gaussian distributions, extending the applicability of the AG model to the propagation of ``real-world'' bunches. During propagation, electron bunches can be shaped by electron-optic devices, which are necessary to attain high brightness, sub-100 fs bunches. I investigate two types of electron-optic devices: one is a magnetic lens used for collimating or focusing bunches, the other is a bunch compressor. I derive bunch parameter transformations for each of the electron-optic devices, and present numerical calculations using these transformations along with the AG model showing the effects of the devices on the evolution of the bunch parameters. To analyse electron bunch diffraction in UED experiments, I present a general scattering formalism. Using single-scattering and far-field approximations, I derive an expression for the diffracted signal that depends on the electron bunch properties just before scattering. Using this expression I identify the transverse and longitudinal coherence lengths and discuss the importance of these length scales in diffraction pattern formation. I also discuss the effects of different bunch parameters on the measured diffracted flux, and present sample numerical calculations for scattering by nanosize particles based on this model. This simulation demonstrates the cumulative effects of the bunch parameters, and shows the complex interplay of the bunch and target properties on the diffracted signal.

Ultrafast electron diffraction (UED) is a method of directly imaging system dynamics at the atomic scale with picosecond time resolution. In this thesis I present theoretical analyses of the experimental processes, and construct models in order to better understand UED experiments and to guide future refinements. In particular, I derive a model of electron bunch propagation and a model of electron bunch diffraction, where both models take into account all bunch parameters. To analyse the propagation of electron bunches, I present a mean-field analytic Gaussian (AG) model. I derive a system of ordinary differential equations that are solved quickly and easily to give the bunch dynamics. The AG model is compared to N -body numerical simulations of initially Gaussian bunches, and I demonstrate excellent agreement between the two result sets. I also present a comparison of the AG model with numerical simulations of quasi-Gaussian and non-Gaussian distributions, extending the applicability of the AG model to the propagation of ``real-world'' bunches. During propagation, electron bunches can be shaped by electron-optic devices, which are necessary to attain high brightness, sub-100 fs bunches. I investigate two types of electron-optic devices: one is a magnetic lens used for collimating or focusing bunches, the other is a bunch compressor. I derive bunch parameter transformations for each of the electron-optic devices, and present numerical calculations using these transformations along with the AG model showing the effects of the devices on the evolution of the bunch parameters. To analyse electron bunch diffraction in UED experiments, I present a general scattering formalism. Using single-scattering and far-field approximations, I derive an expression for the diffracted signal that depends on the electron bunch properties just before scattering. Using this expression I identify the transverse and longitudinal coherence lengths and discuss the importance of these length scales in diffraction pattern formation. I also discuss the effects of different bunch parameters on the measured diffracted flux, and present sample numerical calculations for scattering by nanosize particles based on this model. This simulation demonstrates the cumulative effects of the bunch parameters, and shows the complex interplay of the bunch and target properties on the diffracted signal.

Thesis (M.S. in Applied Physics)--Naval Postgraduate School, December 2009. / Thesis Advisor(s): Colson, William B. ; Blau, Joseph. "December 2009." Description based on title screen as viewed on January 28, 2010. Author(s) subject terms: Free Electron Laser, FEL, misalignment, mirror, electron beam, optical field, cathode, test cell, electron gun. Includes bibliographical references (p. 83). Also available in print.

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No description available.

In the last twenty years, electron-atom scattering theory has witnessed significant theoretical developments. One of these advances is the use of the momentum-space convergent closecoupling approach to fully incorporate target atom continua. This theoretical framework is based on the momentum-space Lippmann-Schwinger equation, an integral form of the Schrodinger equation. Although the approach has been highly successful in its application to atomic scattering theory, computing numerical solutions is inherently difficult because the momentum-space LS equation is a singular integral equation. Standard numerical integration techniques are normally employed to solve the problem and as computing power has increased, calculations have improved. However, there remains the problem of the integral's singular nature, which demands complicated methods for selecting integration points, particularly near the energy-dependant singularity. The rotated-contour method uses a conlplex-variable approach that solves the momentum-space LS equation by integrating along a deformed contour in the complex momentum plane away from the singularities. This method has the potential for simplifying the numerical integrations associated with the close-coupling equations. A rotated-contour method is first applied to a simple scattering model - electron scattering from the Yukawa potential. This gives some insight into the difficulties that arise when calculating potential matrix elements for complex momenta. The method is then applied to the s-wave model of the electron-hydrogen scattering problem and finally, the full problem. Existing FORTRAN software written to solve the momentum-space LS equations for electron-hydrogen scattering using standard techniques has been converted to C++. Extensive modification of the code has resulted in a flexible Windows-based program with a graphical user interface that runs on any modern computer using PC architecture. The program can calculate results using either a conventional method (no rotation) or a rotatedcontour method. Using a rotated-contour method to solve the momentum-space LS equations necessitates detailed knowledge of the analytic nature and singularity structure of the coupled channels potentials. This is achieved through the extensive use of the computer symbolic algebra system Maple to compute closed-form solutions for the direct potentials and for a range of partial-wave direct and exchange potentials. It is found that logarithmic branch point singularities are present on the real momentum axis for an extensive class of partial-wave direct-potential matrix elements. The analysis reveals that arotated contour method cannot be applied to the full atomic scattering problem due to these analytic problems which are associated with the long-range nature of the Coulomb potential.

Thesis (Ph.D.)--Murdoch University, 2005. / Thesis submitted to the Division of Science and Engineering. Includes bibliographical references (p. 175-182).