Abstract
The column of electron electrostatic accelerator is one of the critical components in electrostatic accelerator. The geometrical design of such accelerator must be as such that in the case of applying voltage to its electrodes, not only should its equipotential surfaces and its gradient accelerate the beam particles up to desired energy, but also it should focus the beam and hinder broadening of energy distribution of accelerated particles. The immersed electrodes in the field are, geometrically, perpendicular to optical axis around the medial plane. Numerous models that can be used in the distribution of axial potential, have been presented and linear model, analytical model, double-column electrode model and polynomial electrode model are among them. In this paper, series expansions based on Bessel functions is used to obtain the axial potential distribution of immersed accelerator electrodes in double-electrode field and it is then compared to the mentioned models by solving the final equation via the least square method. Finally, by using CST Studio software and the information we obtained from the axial potential, the column of electron accelerator with its energy distribution and its optimal electron output beam radius is designed and simulated.
Highlights
Application of accelerator is common in many fields such as research, education, industry, medicine [1] and agriculture
The electrostatic electrodes are widely categorized in terms of the potential of their electrodes which contain the main group of Einzel lens [6] [7] [8], which create similar potential in both object part and image part, the immersed lens in the field are immersed in a field with two constant but different potentials in the both sides, a single-span lens with one induced homogeneous field on one side, and the foiled lens [9]
In the second geometry for optimizing of application of accelerator column, the electrodes can be considerated ridged that is shown in Figure 9: The path of the particles for the second geometry in Figure 10(b) and electron energy in the form of Figure 10(a) is given which shows the radius of output beam in second geometer is reduced 2 cm and the energy of electrons is increased in compare with first geometer; So it is better to design the electrodes of 300 keV electron electrostatic accelerator column ridged
Summary
Application of accelerator is common in many fields such as research, education, industry, medicine [1] and agriculture. In order to calculate the axial potential of a lens immersed in field, we consider two flat planes which each of them have holes in them with the diameter of D and they are separated from each other with distance A. In calculations of electrostatic lenses with digital computers, the common way is to solve the Laplace equation [14] There is another solution approach in which the potential is expanded by Bessel functions. The only task that remains is to meet the boundary conditions in z = ± 1 A , in addition we will have to make sure that the potential stays continuous all over the two holes This equation will guarantee that the radial component of the field remain continuous. This will result in converging solutions for Equations (8) and (9) and axial potential V (0, z) which in this case will converge by increasing N
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