Some closed-form expressions for relativistic cross-field electron trajectories
Equations for nonrelativistic cross-field motion are first repeated from prior work, in a form suitable for piecewise trajectory calculation in fields that need not be constant. They are then extended into the middle relativistic range, using a new method of expressing the relativistic cyclotron frequency in terms of the fields and the starting conditions. The extended equations are found to include second harmonic terms, but not third harmonic. Accuracy is tested by comparison with Runge-Kutta integration of the relativistic equations of motion, and is found to be adequate for many engineering purposes up to peak velocities in the region of 0.6 c, corresponding to cross-field tube operating voltages on the order of 400 kV. Speed is similar to or a little better than R-K integration on a per-step basis, but is substantially higher when the fieldsallow large step sizes to be taken, since the closed-form expressions have no inherent step size limitation. The tests covered conditions appropriate both to gyrotrons and to relativistic magnetrons.
Beam buildup in a DEMATRON amplifier
The operation of an RF triggered cold-cathode crossed-field amplifier is briefly described, and the problem is posed of how the beam builds up, since it is necessary for it to remain in an inherently debunching phase region for more than 20 successive impacts on the cathode. A partial answer is provided by numerical calculations showing that the velocity of a repeatedly impacting beam differs from E/B in a way which introduces a new phase-focusing mechanism. It is found that buildup can also occur without exact synchronism over a range of calculated voltages which agree closely with measurement. The principles of two computer programs are described, one covering the buildup region of negligible space charge, and the other the transition and power-generating regions where space charge becomes important. Quantitative conclusions are drawn concerning the velocity and direction of impacts on the cathode, which vary markedly as the space charge density changes.
Investigating the Optical properties of cd1-xznxs thin films deposited by the Dip Technique
A Thesis submitted to the Department of Physics, Kwame Nkrumah University of Science and Technology, in partial fulfillment of the requirement for the degree of 
Master of Science (Solid State Physics)