5 Fiducialization in elegant

In some tracking codes, there is a “fiducial particle” that is tracked along with the beam. This particle follows the ideal trajectory or orbit, with the ideal momentum, and at the ideal phase. There is no fiducial particle in elegant. Instead, fiducialization is typically based on statistical properties of the bunch. This can be performed on a bunch-by-bunch basis, or for the first bunch seen in a run. The latter method must be used if one wants to look at the effects of changing phase, voltage, or magnets relative to some nominal configuration.

Internally, elegant fiducializes each element in the beamline. Fiducializing an element means determining the reference momentum and arrival time (or phase) for that element. If the reference momentum does not change along a beamline and no time-dependent elements are involved, then fiducialization is irrelevant. All elements are fiducialized at the central momentum defined in run_setup.

A number of commands have parameters for controlling fiducialization:

Here are some examples that may be helpful.