Shap3d09.dat, 9th 'shape' file for CPO3D
A split cylinder deflector
An example of a split-cylinder deflector, taken from xmpl3d19
The axis of the deflector system is the z axis, and the system is symmetric about z = 0. The radius is 0.5. The split cylinder has a length of 1. The gaps in the z direction are 0.05 and those in the azimuthal direction subtend 5 degrees.
The voltages are made anti-symmetric about x = 0 and symmetric about y = 0. The deflector plates at +/- x are given the voltages +/-1, while those at +/- y are at 0.
The first electrode to be entered is a 'rectangle that is on a cylindrical surface'. Two of its corners lie on the xz plane and the other two are very near to the yz plane. The program subdivides this rectangle into smaller rectangles that follow a cylindrical surface, forming an almost complete quadrant of a cylinder. After reflection in the x and y planes an almost complete cylinder is formed. The narrow gap or slot at the yz plane has to be present because this plane is defined by the equation x = 0, and the voltage is declared to be antisymmetric about this plane, and so if the number of segments is increased at a later stage the program would give an unwanted subdivision if the two electrodes to touch here, even if they are eventually given the same voltage (as in the present example).
The last two electrodes to be defined are close to being octants of cylinders. After the reflections they become the deflector plates, and again the one that crosses the yz plane has a narrow gap in it.