FORMATION OF IMAGES BY ELECTRONIC BEAMS, WHAT IS EMITTED BY NONCYLINDRICAL CATHODES IN THE MAGNETIC FIELD OF THE MAGNETRON GUN
DOI:
https://doi.org/10.32782/mathematical-modelling/2022-5-1-6Keywords:
electron beam, magnetron gun, electron source, particle dynamics, gradient magnetic field, mathematical modeling, experimental dataAbstract
Consider the possible directions of modification of the magnetron gun as the source of electron flow with cathodes, the shape of which differs from the axially symmetrical cylindrical shape. The object of this work is the study of the parameters of the electron beam emitted by such cathodes during its transport in the intense gradient magnetic field of the solenoid and the construction of the computational model of the movement of the electron flow in the field region. The improvement of the magnetron gun, consisting in the application of intense magnetic fields with the increased gradient of their intensity, makes it possible to consider new phenomena in the spatial picture of the evolution of electron beams, as well as to investigate the influence of the starting characteristics of particles during emission on the type of electron trajectories. The purpose of the research was to create the mathematical and software model of the movement of such electron beams with the energy of tens of keV in magnetic fields of the chosen configuration, to study the formation of images of beam electron trajectories from the initial conditions and the distribution of the magnetic field along the axis of the system. Mathematical and numerical models of experimental data transformation by analytical functions are used. In the paper, based on the Hamiltonian formalism of the motion of electrons in the magnetic field, the software tool was synthesized that allows for numerical modeling of the dynamics of electron flows in a magnetic field of a solenoid. The results of the numerical simulation of the movement of the electron flow are given. The obtained simulation results indicate the possibility of establishing image modes promising for correcting the structural and phase properties of the target material under experimental conditions. The flow of electrons at the output of the magnetron gun undergoes the rearrangement of the radial distribution, which is determined by the type of magnetic field and its gradient in the beam transport channel. At the same time, the shape of the transverse distribution at the start is also transformed according to the influence of the field. In the work, the evolution of the transverse dimensions of the electron beam formed by the magnetron gun from the configuration of the magnetic field in the particle transport channel is numerically studied using examples. It is shown that with the increase in the maximum amplitude and/or field gradient, the effect of radial transformation (focusing or defocusing) of the beam is more pronounced. The given results indicate the possibility of focusing, as well as defocusing, the electron beam emitted by millimeter-diameter cathodes, which can be used to irradiate the surfaces of cylindrical samples placed in the region of the increasing or decreasing magnetic field.
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