7.27 frequency_map

• type: major action command.
• function: compute frequency map from tracking Note that the number of turns tracked is set by the run_control command.
• can use parallel resources (Pelegant)
• Command syntax, including use of equations and subcommands, is discussed in 7.2.

• output — The (incomplete) name of an SDDS file to send output to. Recommended value: “%s.fma”. For the parallel version, particles will be listed in essentially random order. If needed, sddssort can be used to sort particles by initial coordinates.
• xmin, xmax — Limits of grid of initial x coordinates for tracking.
• ymin, ymax — Limits of grid of initial y coordinates for tracking. ymin should be a small, positive value so that there is some betatron oscillation from which to get the tune.
• delta_min, delta_max — Limits of grid of initial δ coordinates for tracking. Note that particles are not centered around the dispersive closed orbit. Hence, the tracking is appropriate to simulation of dynamics from a touschek scattering event.
• nx — Number of values of x coordinate in the grid.
• ny — Number of values of y coordinate in the grid.
• ndelta — Number of values of δ coordinate in the grid.
• verbosity — If nonzero, prints possibly useful information while running.
• include_changes — If nonzero, then computes not only the tunes, but also the changes in the tunes. This is expressed in terms of the diffusion, which is defined as

  (4)

  where Δν_x and Δν_y are respectively the differences in x and y tunes from the first and second half of the tracking (the total number of turns is equal to the value set in run_setup). The diffusion rate,

  (5)

  is also computed. d_r is the more conventional quantity, computed by programs such as TRACY and MAD [53].

• quadratic_spacing — If non-zero, the spacing of points is quadratic rather than linear, thus emphasizing the higher amplitude regions.
• full_grid_output — If non-zero, all grid points are represented in the output file, even if tracking or tune determination failed. This makes it possible to plot with programs (e.g., sddscontour) that require a strictly uniform grid.