11.5 computeRBGGE

• description: Compute generalized gradients [37] from data on a rectangular boundary [38] for use with elegant’s BGGEXP element. When a full three-dimensional field map is available, it is better to use computeLBGGE, which produces significantly better fits to the field map.
• synopsis:

  computeRBGGE -yminus=<filename> -yplus=<filename> -xminus=<filename> -xplus=<filename> -normal=<output> [-skew=<output>] [-derivatives=<number>] [-multipoles=<number>] [-fundamental=<number>] [-evaluate=<filename>] [-autotune=<3dMapFile>[,significance=<fieldValue>][,minimize=rms|mav|maximum] [,radiusLimit=<meters>][,increaseOnly][,verbose][,log=<filename>] [,minDerivatives=<number>],[,minMultipoles=<number>]]

• switches:
  • yplus — SDDS file containing x, y, z, and By, map stored in columns for positive-y plane. If skew components are desired, file must also supply Bz. Units are meter and Tesla.
  • yminus — SDDS file containing x, y, z, and By, map stored in columns for negative-y plane. If skew components are desired, file must also supply Bz.
  • xplus — SDDS file containing x, y, z, and Bx, map stored in columns for positive-x plane. If skew components are desired, file must also supply Bz.
  • xminus — SDDS file containing x, y, z, and Bx, map stored in columns for negative-x plane. If skew components are desired, file must also supply Bz.
  • normal — Output file for normal-component generalized gradients. Supply to NORMAL_FILENAME parameter of BGGEXP.
  • skew — Output file for skew-component generalized gradients. Supply to SKEW_FILENAME parameter of BGGEXP. NB: if B_z is non-zero on axis, this option is essential in getting valid results.
  • derivatives — Number of derivatives vs z desired in output. Default: 7
  • multipoles — Number of multipoles desired in output. Default: 8
  • fundamental — Fundamental multipole of sequence. 0=none (default), 1=dipole, 2=quadrupole, etc.
  • evaluate — Asks to evaluate the GGE and place the results in a file. The GGE is evaluted over the region bounded by the four planes, using the same coordinate intervals.
  • autotune — Optimizes the number of derivaties and multipoles up the to values given with the -derivatives and -multipoles options, in order to minimize the deviation of the GGE-derived fields from the values given in the 3D field map file. The region of evaluation is automatically limited by the bounding planes, even if the 3D field map has a larger extent. By default, minimizes the maximum deviation, but user can ask to minimize the rms or mean-absolute-value deviation. Differences below the significance value are ignored. The user may request verbose output to see results printed to the terminal, and also a log file for a detailed record. The increaseOnly qualifier specifies that the scan over multipoles m and derivatives d is restricted to never be less than the previous optimal values; for example, if the best value so far was obtained with m = 4 and d = 3, the remainder of the scan would be restricted to m ≥ 4 and d ≥ 3; this can save considerable run time. The minDerivatives and minMultipoles parameters allow requiring the auto-tuner to use a mimimum number of derivatives and multipoles, respectively; by default, as few as 1 of each might be used.
• authors: R. Lindberg, R. Soliday, M. Borland (ANL/APS).