A ring model of the Lasertron

The lasertron is a device to transform high voltage power to microwaves, and it is much like a klystron with a photocathode. The beam is bunched in the lasertron by the laser light that is modulated at the microwave frequency. The photoelectrons are produced at a cathode, and accelerated to a fairly high voltage in the gun region by an electric field. These electrons produce microwaves in the output section, which is one or more cavities that decelerate the beam with the microwave fields. The purpose of this paper is to develop a computer model of the lasertron. This model can be used to predict general trends in lasertron performance on the device parameters, and the model can also be used to design lasertrons for particular applications. The ring model of the electrodynamics in the klystron has recently been written. The main features of the ring model of the lasertron are as follows. The relativistic electron dynamics of a set of particles are followed from the photocathode through the gun region and through the output region, with time as the independent variable. The fields are summed by superposition to find the total field at each electron's position. The model is 2 1/2 dimensional. A single bunch of electrons is followed through the lasertron. The program is modular and flexible, so many of the fields can be approximated in several ways to alter the accuracy and time requirements to perform the simulation. The particles all have the same charge, so the laser light pulse is assumed to be rectangular. All processes in the photo cathode are assumed instantaneous. The beam model is a central disk surounded by rings. This combination starts at the cathode in a plane, and is repeated many times over the length of the laser pulse