The CWIGGLER element now supports imposition of uniform horizontal and vertical magnetic
fields. These can be used, for example, for trajectory correction.
The calculation of the Bassetti-Erskine formula, used for obtaining the electric field for
gaussian bunches, is now faster by about a factor of two, thanks to use of code from
http://ab-initio.mit.edu/Faddeeva. This change by N. Kuklev (APS) affects the IONEFFECTS
and BEAMBEAM elements.