Do you design and build vacuum electron devices, or work with the systems that use them? Quickly develop a solid understanding of how these devices work with this authoritative guide, written by an author with over fifty years of experience in the field. Rigorous in its approach, it focuses on the theory and design of commercially significant types of gridded, linear-beam, crossed-field and fast-wave tubes. Essential components such as waveguides, resonators, slow-wave structures, electron guns, beams, magnets and collectors are also covered, as well as the integration and reliable operation of devices in microwave and RF systems. Complex mathematical analysis is kept to a minimum, and Mathcad worksheets supporting the book online aid understanding of key concepts and connect the theory with practice. Including coverage of primary sources and current research trends, this is essential reading for researchers, practitioners and graduate students working on vacuum electron devices.

Microwave and RF Vacuum Electronic Power Sources

A method of calculation of coupled-cavity TWT performance which is programmable for fast and economical calculation on a time-sharing computer is presented. The tube is modeled as a sequence of interaction gaps and tunnels, with cavities associated with each gap. The fields are expanded in terms of a sequence of stationary waves anchored on each gap, instead of a set of traveling waves. Space-charge forces are calculated by a fast potential-gradient method instead of from a Green's function. These methods allow flexibility in the model as well as speed. The method is applied to three simple examples, to show the behavior of components of a TWT, and then to two actual designs.

Calculation of coupled-cavity TWT performance

An accurate three-dimensional analysis of the performance of output gaps in klystron amplifiers was carried out The parameters investigated were: beam radius, perveance, output gap angle, output gap peak voltage, RF phase, magnetic field, and beam interception A new, accurate method for computing space-charge forces between axially and radially deformable rings was developed Rigorous expressions for electric and magnetic fields in the tunnel and the gap were used The highest computed efficiency for an optimally bunched beam was 803 percent with 6 percent "ideal" interception An important conclusion is that efficiency decreases with increasing normalized tunned radius \beta_{e}a for b/a constant in the examined range 04 and probably beyond Excellent correlation in efficiency and interception between a model klystron developed by E Lien of Varian and the authors' program was established

Three-dimensional evaluation of energy extraction in output cavities of klystron amplifiers

This paper describes the development of a one-dimensional large signal (nonlinear) model for helix travelling wave tubes (TWTs). Lagrangian formulation (large-particle method) has been used to model the electron beam in terms of the well defined cylindrical charged discs. The motion of each charged disc is tracked, in small distance steps down the tube, in presence of the rf circuit field and the space charge field forces. The helix slow wave structure has been represented by generalised transmission line for defining the circuit field and for calculating the energy transfer from the modulated beam to the circuit. The large signal model is self-consistent and fast enough for interactive use. The internal energy balance check is typically satisfied within 1 per cent of the input beam power even beyond saturation, showing high numerical accuracy of the model. The program takes less than 3 minutes in one pass through a tube of length nearly 30 beam wavelengths for number of discs per rf cycle 24 and number o...

One-Dimensional Nonlinear Model for Helix TWTs

For the design of a high-performance broad-band klystron, an accurate large-signal analysis is made. By a one-dimensional analysis program using a disk model of the electron stream, the interaction between a bunched electron beam and the electric field in each cavity gap is studied, taking into consideration space-charge forces, relativistic effects, and electric field distributions in ungridded gaps; beam loading is included by an iterative method at each intermediate gap, and the energy exchange in the output gap is obtained from the change in kinetic energy. On the five-cavity UHF-TV klystron designed with this program and having a conversion efficiency of over 60 percent, the debunching effect of the electric field in intermediate cavity gaps and the behavior of vibrating electrons in the output gap are clarified. Calculated conversion efficiency is shown to agree well with measured efficiency over the pass-band. Additionally, by a two-dimensional analysis program, the effect of the cathode magnetic coefficient on the electron bunching is studied.

A large-signal analysis of broad-band klystrons with design applications

The potential energy stored in a bunched electron beam is calculated using analytical and numerical methods. The ratio of stored potential energy to the total beam energy W_{p}/W_{0} increases rapidly with the degree of bunching and with decreasing beam filling factor b/a . W_{p}/W_{0} is proportional to the beam perveance and independent of the beam voltage, as long as relativistic effects are neglected. In a velocity-modulated linear beam-type device, such as a klystron or a traveling-wave beam tube, stored potential beam energy affects both the bunching process and the process of dc to RE energy conversion adversely. For maximum conversion efficiency W_{p}/W_{0} should be kept as low as possible. Several ways of reducing W_{p}/W_{0} are discussed.

J.R. Hechtel

Papers

The effect of potential beam energy on the performance of linear beam devices