Gaussian Bunch Research Articles

Energy Losses of an Electron Bunch Moving along the Axis of a Circular Waveguide with Periodically Perturbed Wall

The field radiated by an electron bunch moving along the axis of a circular periodic waveguide is obtained from Maxwell's equations using a perturbation method. The guide shape is defined by its radius a(z) = ao {I + εs(z)} where ao denotes the mean guide radius, s(z) the guide geometry and ε a small perturbation parameter. Electromagnetic field is calculated up to second order in ε . The total energy loss suffered by the bunch and the potential acting on individual particles are related to the following parameters : charge, shape and width of the bunch, energy, guide geometry, by comparatively simple formulas. The influence of these parameters is calculated for a gaussian bunch and a rounded iris waveguide. This example clarifies under what conditions energy losses are virtually independent of energy and shows the importance of the bunch width.

Diffraction of a wave bunch on a plasma cylinder

A METHOD for the numerical solution of the two-dimensional problem of the diffraction of an electromagnetic wave by a plasma cylinder, whose dielectric constant is a function of the radius-vector r, being unity for large values of r, is described. In this problem the fields are represented by series of azimuthal harmonics, the corresponding radial functions being found by numerical integration of second-order linear differential equations with singular points. A calculation is made of the result of this averaging of the Green's function over the coordinates of the source and point of observation, which corresponds to the irradiation of the plasma by an antenna creating Gaussian wave bunches, and to the reception of the diffraction field by a similar receive antenna. Numerical results are given, and the principal physical phenomena arising on the diffraction of a wave bunch by a plasma cylinder are discussed.

A non-linear theory of acoustoelectric gain and current in piezoelectric semiconductors. III. The Gaussian electron distribution

For pt. II see A16173 of 1969, B7833 of 1969. The electron bunches formed in a periodic acoustic travelling wave are shown to have an approximately Gaussian shape at high flux levels. Plots are given, for Gaussian bunches, of the relevant gain parameters against a bunching parameter related to the half- width of the bunches. For 7*10-2 Omega m cadmium sulphide the peak total flux gain and the peak first harmonic gain in a d.c. field of 4.8*105 v m-1 are reduced to 2.5% and 8% of their small signal values, respectively, at a flux level of the order of 108 wm-2. In both cases the frequency at which the peak gain occurs is reduced to 25% of the small signal value.