xmpl3d08, 8th 'example' data file for CPO3D
Space-charge repulsion in a mixed beam of electrons and positively charged carbon ions.
Simulation of the space-charge repulsion of a mixed beam of electrons and positively charged carbon ions. The electron and ion beam currents have been made equal and opposite, and the electrons and ions have been given the same velocity. The combined space charge should therefore be zero, and both types of particle should travel in straight lines. This behaviour is accurately reproduced.
The following data were obtained when the memory and speed of PC's was much more limited than at present, so the available number of segments was small and the requested inaccuracies were fairly high to give a quick demonstration.
The set-up is almost the same as in example file xmpl3d07.dat, except that the beam is a mixture of electrons and positively charged carbon ions (see note on masses).
There are 12 electron rays and an identical 12 ion rays, all directed towards the origin (and the starting conditions have been obtained by running xmpl3d07.dat with 12 rays and then editing the ray information in the output file temp7a.dat).
The electrons are given an energy 1 eV, an atomic mass number 0.0005486 (=1/1822.9) and a charge number -1, while the carbon ions are given an energy 12*1822.9 eV, a mass number 12 and a charge number +1. The electrons and ions therefore have the same velocity. The ray currents are the same for the carbon ions and the electrons. The combined space charge is therefore be zero, and both types of particle can be seen to travel in straight lines.
As another test of the 'variable mass' option delete the 12 ion rays. The space-charge repulsion in the electron beam will then be similar to that obtained with the example file xmpl3d07.dat.
As a test of the 'constant mass' option, use the same disc source of rays given in xmpl3d07.dat, but replace the line that starts with 'va' by a line that starts with 'co' and follow it with the line '1.0 12.0'. Also scale down the currents by the square root of the mass -that is, divide them by sqrt(12*1822.9). The shape of the beam will then be similar to that obtained with the example file xmpl3d07.dat.