Example of simulating multi-bunch effects of linac with cavity modes with 
control of the energy profile. Using CHANGE_P0=1 is normal for linacs in
ELEGANT, but that means elegant adjusts the energy profile for the bunch
train being simulated. As more bunches are added, there is more beam-loading
and hence the energy profile changes. This changes the effective strength
of the quadrupoles, for example, which may not be realistic.

Example by J. England (SLAC) and M. Borland (APS).

LCLS2scD_multibunch.lte
        Lattice file
ModesX.sdds
ModesY.sdds
ModesZ.sdds
        Cavity modes
UMHTR.rmat
        Matrix for undulator.
xWake_1.3GHz_OneCavity_dz2um_TESLA2003-09.sdds
xWake_3.9GHz_OneCavity_dz2um_TESLA2004-01.sdds
zWake_1.3GHz_OneCavity_dz2um_TESLA2003-09.sdds
zWake_3.9GHz_OneCavity_dz2um_TESLA2004-01.sdds
        Wake files.

REF_WL4BEG_1k.sdds
        Bunch phase space input file.

run1.ele
runCase1
        Runs a single bunch to get the reference momentum profile.
        The script processes the profile to make a parameter file that
        can be used to force elegant to use the same profile in other
        simulations.

runTemplate.ele
runCase
        Runs a case with a given number of bunches, using the reference
        momentum profile determined in run1.

runSeries
        Runs case 1, then a series of cases with different numbers of bunches,
        then processes and plots some centroid properties vs bunch number.

cleanUp
        Cleans up run output files.
