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General Tips

At the end of this section some general hints and tips are listed. There are in no particular order or relation to each other.

  • Time-dependent simulations are very CPU-expensive. To optimize an input deck, try to do it in steady-state mode (ITDP=0).
  • The calculation of the diffraction angle of the radiation field as part of the diagnostic is CPU intensive and not needed for the simulation itself. To speed up the execution it is better to save the radiation field at various locations along the undulator. The diffraction angle can then be obtained in a post-processing step.
  • The output of the particle and field distributions can generate huge output files. Although GENESIS 1.3 warns about large output files it does not check the available space of the hard disk. Either run GENESIS 1.3, check for warning about large output files and stop the program (if the space is not available) or reduce the size of the output file by increasing the value of IPRADI, ISRADI, IPPART and/or ISPART.
  • Avoid to use the same parameter several times in the input deck. GENESIS 1.3 will use the last occurrence in the input deck or might even report an error and quit.
  • Check whether space charge has a significant impact on the result of the steady-state case. Space charge can be disabled by setting NSCZ to zero. If the results are not effected by the space charge routine time-dependent simulations excluding the space charge routine run faster.
  • For runs with different field errors change the value of ISEED before each run. The same is valid for the phase fluctuation in SASE simulations where IPSEED has to be changed.
  • Although the loading parameters ILDPSI, ILDGAM, ILDX, ILDY, ILDPX and ILDPY need hardly to be changed at all, do not assign the same number to more than one parameter.
  • It is recommended to set the VERSION parameter to the latest version number to avoid unexpected behavior (e.g. IDUMP=1 will not dump the particle distribution if VERSION is smaller than 1.0).
  • ZRAYL and ZWAIST are needed to calculated the grid size for the simulation although their primary meanings are obsolete for SASE simulation. If DGRID is used and PRAD0 is very small than indeed they have no impact on the simulation. Still ZRAYL is required to be larger than 0.