tune_footprint

- type: action/setup command.
- function: compute frequency map from tracking and use it to determine the chromatic and amplitude tune footprints.
- sequence: must follow
`run_control`

. - N.B.: the number of turns tracked is set by the
`run_control`

command.

&tune_footprint STRING delta_output = NULL, STRING xy_output = NULL, double xmin = -0.02, double xmax = 0.02, double ymin = 1e-6, double ymax = 0.02, double x_for_delta = 1e-6, double y_for_delta = 1e-6, double delta_min = 0, double delta_max = 0, long nx = 20, long ny = 21, long ndelta = 21, long verbosity = 1, long quadratic_spacing = 1, long diffusion_rate_limit = -5, long immediate = 0 &end

`delta_output`

-- The optional (incomplete) name of an SDDS file to send tune and diffusion rate vs output to. Recommended value: ``%s.dtf''. If optimization is done, this file is written only at the end of optimization.`xy_output`

-- The optional (incomplete) name of an SDDS file to send tune and diffusion rate vs (x, y) output to. Recommended value: ``%s.atf''. If optimization is done, this file is written only at the end of optimization.`xmin`

,`xmax`

-- Limits of grid of initial x coordinates for tracking.`ymin`

,`ymax`

-- Limits of grid of initial y coordinates for tracking.`ymin`

should typically 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 coordinates for tracking. Not that particles are not centered around the dispersive closed orbit.`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 coordinate in the grid.`verbosity`

-- If nonzero, prints possibly useful information while running.`quadratic_spacing`

-- If nonzero, points are spaced ``quadratically,'' which actually means that their squares are spaced linearly. It is highly recommended to keep this turned on, since otherwise problems determining the tune when may result in invalid results.`diffusion_rate_limit`

-- Value of the diffusion rate above which the particle is considered unstable, where

(5) `n_passes`

).`immediate`

-- If nonzero, the calculations take place immediately, instead of only during optimization. If you wish to compute Twiss parameters on a closed orbit or after other calculations, be sure to set this control to zero.

This command makes available the following quantities for optimization. All quantities are limited by particle survival, crossing of integer and half-integer resonances, and the diffusion rate limit.

`FP.nuxSpreadChrom`

,`FP.nuySpreadChrom`

-- Spread in tunes due to chromaticity.`FP.deltaLimit`

-- Minimum of absolute values of positive and negative limits.`FP.nuxSpreadAmp`

,`FP.nuySpreadAmp`

-- Spread in tunes due to amplitude.`FP.xSpread`

,`FP.ySpread`

-- Spread in x and y values.`FP.xyArea`

-- Area of the limited x-y region, comparable to a dynamic acceptance. However, this area is determined from a fixed grid and is not suitabl to optimization by itself.`FP.diffusionRateMaxChrom`

,`FP.diffusionRateMaxAmp`

-- Maximum diffusion rates in chromatic and amplitude scans.

`FP.nuxSpreadChrom`

,`FP.nuySpreadChrom`

,
`FP.nuxSpreadAmp`

, `FP.nuySpreadAmp`

, `FP.diffusionRateMaxChrom`

,
and/or `FP.diffusionRateMaxAmp`

while maximizing `FP.deltaLimit`

, `FP.xSpread`

, and/or `FP.ySpread`

, and
ensuring that `FP.xyArea`

, at minimum, doesn't decrease.
I.e., one wants the maximum stable region for momentum and position deviations with the minimum spread in tunes and minimum diffusion.