61st example file for CPO3D.

Illustration of the 'User-supplied near-axis electric field' option.

Here a central cylinder is split into 8 parts that can be used as a quadrupole, octupole or monopole (ie round) lens.

The 'related voltages' option is used so that the multipolarity of the lens can be easily changed.

With the values given above all 3 multipolarities are activated together, each with a voltage 1V.

The User-supplied routine is user3d.cpp.  A read-only copy is in use3copy.cpp.  The 2 files that are read by user3d.cpp are userfld1.dat and userfld2.dat, which are given in the footnotes to the data file.