csrImpedance

• description: Computes the steady-state CSR impedance with shielding by parallel plates. By default, the computed impedance is for a dipole magnet that bends the beam in a complete circle.

• synopsis:
  csrImpedance outputFile | -pipe[=out] -height=valueInMeters -radius=valueInMeters -frequencyLimit=maximum=valueInHz[,minimum=valueInHz] -n=integer [-filter=cutoff1,cutoff2] [-angle=radians]

• files:
  • outputFile -- SDDS file containing computed impedance. May be used directly with elegant's ZLONGIT element. as columns, along with analysis and conditions as parameters.

• switches:
  • -height -- The full height of the vacuum chamber, in meters.
  • -radius -- The radius of the bending magnet, in meters.
  • -angle -- The angle of the bending magnet, in radians. The default is $2\pi$.
  • frequencyLimit -- Allows specifying the upper frequency limit (required), as well as the lower frequency limit, for the computed impedance. elegant will not accept the data if the lower limit is not 0. If the rms bunch length is $\sigma_t$, then it is suggested to have the maximum frequency much greater than $1/(2\pi\sigma_t)$.
  • -n -- Allows specifying the number of data points to be computed. The number of points computed is $2^n+1$, which is required by elegant. A reasonable value is $n=10$ to $n=14$.
  • -filter -- Allows specifying the starting and ending frequency for a simple low-pass filter. The frequencies are given as fractions of the maximum frequency. The filter ramps linearly from 1 to 0 between the two cutoff values. If, for example, the cutoff is 0.2, then the highest frequency in the impedance corresponds to a wavelength of 10 bins ($2/0.2$) in elegant.

• authors: Y. Wang, H. Shang, ANL/APS. Based on a simplified form[26] of Warnock's [25] formula.