Section 2.8 of the User's Guide for CPO2D and CPO3D

Or proceed to section 2.9


Specifying the initial ray conditions.


The starting conditions of the rays can be specified in a wide variety of different ways, including beams, cathodes and simply specifying each individual ray.


The ray (that is, trajectory) initial conditions can be entered in any of the following ways:

(1) by specifying a series of individual rays

(2) by specifying a beam (that is, a bundle of rays)

(3) by specifying a set of lens or spectrometer coefficients that are to be calculated

(4) by calling for a repeat (during a space-charge iteration) of the previous set of rays, together with a multiplication factor for the currents

(5) by specifying the parameters of a thermionic cathode

(6) by specifying the parameters of a field emission or schottky emission cathode.

(7) by calling for an iteration. (of a cathode space-charge calculation)

(8) by specifying the parameters for zero initial kinetic energy.

(9) by calling for a re-plot of the previously calculated rays.


It is also possible to by-pass the ray tracing process and re-use previously calculated rays.


It is also possible to combine sets of rays.


The colours of the rays can be chosen by the user.


In space-charge simulations each ray represents a model particle that moves in the total electric field as if it were a single electron or ion but carries the charge and current of many adjacent electrons or ions. The model particle has sometimes been labelled a super-electron or ion.



Other options that appear on the ‘sources of rays…’ screens:


Secondary electrons.

Scattering option.

Stochastic option.


The space charges of the rays are dealt with by either the tube or cell methods (of which the tube method is usually the most suitable).


See also advanced options in setting up rays.