Specification of ray reflections.

# See also the general notes on symmetries and reflections.

After the rays have been traced, but before they are displayed on the screen in the 2D plots in CPO2D, or 2D and 3D plots in CPO3D, they can be reflected (if planes of symmetry or an axis of symmetry exist), as specified by the user. But they cannot be reflected if the voltages are time-dependent. If there are space-charges they will automatically be reflected (see the general notes on space-charge), with no action required from the user.

In CPO2D rays are usually only reflected in planes that pass through the axis of the beam (that is, transversely to the direction of the beam).

In CPO3D the 4 planes through which the rays can be reflected before they are drawn on the screen are the 4 allowed symmetry planes, namely the yz (that is, x = 0), zx (that is, y = 0), xy (that is, z = 0) and x = y planes.

A plane through which rays are reflected must also have been declared at the beginning of the program as a plane of positive voltage reflection symmetry.

The beam section also contains the crossing points of the reflected rays (unless the beam section plane is inclined in such a way that these reflections are not appropriate for the beam section).

For users who are editing or constructing an 'input data file' without the use of the data-builder -that is, pre-processor:

But Manual editing is certainly not recommended -it is a relic from the time when the databuilder was not available All users are strongly encouraged to use the databuilder, which always gives the correct formats and which has many options for which the formats are not described or easily deduced.

The line that specifies the reflections must be entered unless:

# (1) the voltages are time-dependent, or

(1) a magnetic field is specified, in CPO3D, (in which case the reflection symmetries of rays in a magnetic field have already been dealt with, or

(2) there are space-charges, in which case the rays will automatically be reflected (see the general notes on space-charge), and this line is therefore not needed.

# In CPO2D:

If you do not want to reflect the rays, enter '0 0' at the beginning of the line. If you want the calculated rays to be reflected through the z axis (so that the point (r,z) becomes the point (-r,z) in cylindrical symmetry, or (x,z) becomes (-x,z) in planar symmetry), then put 1 in the first space.

If you want the calculated rays to be reflected through the z = 0 plane (so that the point (r,z) becomes the point (r,-z) etc), then put 1 in the third space. You must therefore enter either '0 0', '1 0', '0 1', or '1 1'. If you enter '1 1' then 3 extra sets of rays will be produced, for reflection in r only, z only, and simultaneously in r and z.

# In CPO3D:

Enter 1 for each plane at which the rays should be reflected (otherwise put 0). All combinations of the reflections will be used.