Design of optimum Faraday cages for collector depression of microwave tubes

The study of various experimental system using collector depression. led to the development of an analytical method for obtaining the collection efficiency and the power dissipation density of Faraday cages of arbitrary shape. This method is based on the solution of a Fredholm integral equation for the emission density on the walls of the multiply reflected secondary electrons. This technique has been used to analyse certain specific experimental systems, and good agreement with the experimental results has been found. In addition, new collector designs have been developed with the aim of improving collection efficiecies and obtaining more uniform power dissipation densities. The use of a small transverse magnetic field can cause a considerable improvement as will be demonstrated by specific examples. In particular, this is a valuable method for multiple-potential collector depression systems. A small reversing transverse magnetic field at the entrance to the Faraday cage has also been studied and it has been found that this is a good method for preventing backstreaming electrons from introducing an increase in noise.