Ray space charges.
The user has the choice of two methods for dealing with the space charges of the rays. They are called the 'cell' and 'tube' methods -and the 'tube' method is usually the most suitable.
The 'tube' method is usually the more suitable for general use, especially when the beams are long and narrow.
The 'cell' method is suitable when the beams are not long and narrow.
Both methods require the user to choose a 'distance parameter'.
For rays that start from cathodes, see notes on specifying a 2D cathode or specifying a 3D cathode and on 2D cathode iterations or 3D cathode iterations.
For non-cathode space-charge rays, see note on 2D space charge iterations or 3D space charge iterations.
Reflection symmetries:
The program assumes that the rays all start in the minimum sector, so the user must be careful to ensure this.
In the cell method the program puts all the cells into the minimum sector.
The program automatically reflects the rays and their space charges in all the symmetry planes of the segments and surface charges.