About Genesis
Input Parameters
Input Files
Getting Started
3rd Party Programs
Input File Library
Other Links

Step VI - External Magnetic Field

One of the strength of GENESIS 1.3 is the usage of external input files for a more flexible description of the FEL such as a more complicated magnetic lattice. The best way to start using magnetic field input files is to generate one by GENESIS 1.3. This is done by specifying in MAGOUTFILE the name of the file to be generated. This file can be edited to set up the undulator. Using the two section undulator from above (AWD=0.85, XLAMD=0.02) the file contains the lines

AW 8.5000E-01 2.0000E-02 100
AW 0.0000E-01 2.0000E-02 20
AW 8.5000E-01 2.0000E-02 100
AW 0.0000E-01 2.0000E-02 20

Example: To remove the gaps and to taper the second module so that the field strength is 5% smaller change the lines to

AW 8.5000E-01 2.0000E-02 120
AW 8.0750E-01 2.0000E-02 120

The modified file can then be loaded into GENESIS 1.3 for the next run. The filename of the edited file is assigned to MAGINFILE. It is recommended to remove the parameter MAGOUTFILE from the input deck or change the assigned filename before running the simulation. Otherwise the file is overwritten again. In this case it does not matter but there are some cases (e.g. field errors) where there are subtle difference in the file used for the input and the overwritten output. For more information refer to the section on input and output files.