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##

closed_orbit

- type: setup command.
- function: set up for computation of the closed orbit.

&closed_orbit
STRING output = NULL;
long output_monitors_only = 0;
long start_from_centroid = 1;
long start_from_dp_centroid = 1;
double closed_orbit_accuracy = 1e-12;
long closed_orbit_iterations = 10;
double iteration_fraction = 1;
long fixed_length = 0;
long start_from_recirc = 0;
long verbosity = 0;
&end

`output`

-- The (incomplete) name of an SDDS file to which
the closed orbits will be written. Recommended value: ``%s.clo''.
`output_monitors_only`

-- If non-zero, indicates that the
closed orbit output should include only the data at the locations of
the beam-position monitors.
`start_from_centroid`

-- A flag indicating whether to
force the computation to start from the centroids of the beam
distribution.
`start_from_dp_centroid`

-- A flag indicating whether to
force the computation to use the momentum centroid of the beam
for the closed orbit. This can allow computing the closed orbit
for an off-momentum beam, then starting the beam on that orbit
using the `offset_by_orbit`

or `center_on_orbit`

parameters
of the `track`

command. In contrast to the `start_from_centroid`

,
this command doesn't force the algorithm to start from the beam
transverse centroids.
`closed_orbit_accuracy`

-- The desired accuracy of the
closed orbit, in terms of the difference between the start and end
coordinates, in meters.
`closed_orbit_iterations`

-- The number of iterations to
take in finding the closed orbit.
`iteration_fraction`

-- Fraction of computed change that
is used each iteration. For lattices that are very nonlinear or close
to unstable, a number less than 1 can be helpful. Otherwise, it only
slows the simulation.
`fixed_length`

-- A flag indicating whether to find a
closed orbit with the same length as the design orbit by changing the
momentum offset.
`start_from_recirc`

-- A flag indicating whether to
compute the closed orbit from the recirculation (`recirc`

)
element in the beamline. In general, if one has a recirculation
element, one should give this flag.
`verbosity`

-- A larger value results in more printouts
during the computations.

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** Up:** Namelist Command Dictionary
** Previous:** chromaticity
Robert Soliday
2014-03-21