Xmpl3d24, 24th 'example' data file for CPO3D
CRT electron gun, cylindrical symmetry
To illustrate some options.
This is an approximate design, with only a few segments, to give a quick demonstration. No attempt has been made to optimise the system.
A simple tetrode design.
The 'ray space charge tube' method of assigning space charge is used.
The 'phase space' option is also used.
Two measures are taken to try to avoid the high anode potential from affecting the potentials in the cathode region --the 'zero total charge' option is disabled and an extra electrode is placed behind the cathode.
6 iterations are called, with a final total current (before symmetry refls) of -1.436mA. After several further iterations this converges to -1.434 mA.
The 'phase space' option gives the following approximate root-mean-square ranges of coordinate and velocity phase space, and the z position of the minimum of coordinate phase space, for x and then y direction (assuming a field-free region):
2.94E-03 7.39E+03 2.4908E-01
2.94E-03 7.39E+03 2.4908E-01
Therefore according to this the focus or disc of least confusion effectively has a radius of approximately 2.9 micrometres, at z = 0.249 mm. However, this region is not field-free and it can be seen from the final figure that the beam waist is slightly further to the right, at approximately z = 0.265mm.