7.14 chaos_map

• type: major action command.
• function: compute chaos 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.
• NB: this feature is new in 2019.4 and somewhat experimental. Please report problems on the forum.

• output — The (incomplete) name of an SDDS file to send output to. Recommended value: “%s.cmap”. 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.
• forward_backward — If non-zero, uses the forward/backward integration technique of Y. Li et al. [56]. The number of passes tracked is still controlled by the n_passes parameter of run_control. In addition, the number of iterations of forward and backward tracking is given by the value of forward_backward. If zero, a less interesting technique is used that computes the change in J_x and J_y from tracking with small changes in initial conditions.
• change_x, change_y — If forward_backward is zero, gives the perturbation to initial x and y used to assess chaotic motion from divergence of trajectories.
• verbosity — If nonzero, prints possibly useful information while running.