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.