George D. O'Neill

Bio: George D. O'Neill is an academic researcher. The author has contributed to research in topics: Space charge & Capacitance. The author has an hindex of 1, co-authored 1 publications receiving 6 citations.

On the Space‐Charge‐Limited Current between Nonsymmetrical Electrodes

Abstract: The validity of employing an equivalent symmetrical anode for expressing the space‐charge‐limited current between nonsymmetrical electrodes is examined. It is shown that when the equivalent anode is determined by the capacitance, the error in the expression for the current is usually quite small and its approximate magnitude may often be anticipated. Exact expressions for the capacitance of some basic electrode arrangements are given, followed by a brief resume of corrections required for interpretation of experimental data.

Applying Conformal Mapping to Derive Analytical Solutions of Space-Charge-Limited Current Density for Various Geometries

Abstract: While exact analytic solutions for space-charge-limited currents (SCLCs) are well-established for parallel plate geometries, they have only recently been derived for concentric cylindrical and spherical geometries using variational calculus (VC). However, actual diode systems and slow-wave structures are usually more complicated, making SCLC calculations more difficult. In this article, we apply conformal mapping to derive the analytical solutions for SCLC for various complicated geometries exhibiting curvilinear flow. We first replicate the exact solution of SCLC for concentric cylindrical electrodes from VC using conformal mapping to transform from the Child–Langmuir (CL) law for a planar geometry. We then derive SCLC in other geometries using conformal transformations to either the planar or the concentric cylinder solution. Because the SCLC calculated using such conformal mappings depends only on the CL law, this may permit future incorporation of relativistic or quantum corrections to determine the appropriate relationships for more complicated geometries.

Electron Guns and Focusing for High-Density Electron Beams

Abstract: Publisher Summary The incorporation of a high-density electron beam in an electron tube poses two problems: the design of an electron gun capable of providing a sufficient number of electrons, and the selection of an efficient method of holding the resulting electron beam together in the face of space-charge forces and other effects leading to divergence This chapter describes the principal methods by which these two problems can be solved and provides a critical review of the various suggestions that have been made to improve these methods or to replace them by new techniques It describes the Pierce method and evaluates several methods of arriving at a Pierce gun by alternate design procedures, which are thought to be more systematic than that proposed originally Other interesting configurations that differ from Pierce's are evaluated in the chapter To describe the methods of counteracting beam spreading three schemes are presented in the chapter: (1)the magnetic field surrounds the entire tube, so that the cathode is immersed in the field; (2) the magnetic field is excluded from the cathode by a ferromagnetic shield; and (3) the magnetic focusing field is periodic in nature, being produced by a series of magnetic lenses of alternating polarities

The grid lens effect in convergent Pierce guns

Abstract: In a conventional Pierce-type gun, the anode aperture causes a potential reduction in the cathode-anode region from the ideal Langmuir potential distribution. For low-voltage gating of the electron beam, a mesh grid of spherical shape (conforming to an equipotential surface) is used in front of the cathode. When this grid is operated at the Langmuir potential depicted by its relative position, there is a difference in the potential gradients on its two sides. This difference causes a lens action at each mesh element which results in a displacement of the actual electron trajectory from the ideal laminar trajectory in the region beyond the anode. A means for calculating these displacements as a function of distance along the axis is developed. As the grid lenses are divergent, the images of the mesh elements in any plane beyond the anode are larger than those for ideal laminar flow, resulting in a current density distribution which differs from that of the ideal beam. A means of calculating the current density profile by summing the effects of the grid lenses is devised, and the method is applied to a sample gun design to illustrate the effect on the current density distribution.