4.4 load_fields

• description:

  Allows loading fields from a previous spiffe run. The fields are stored in a file created with the save_fields command.

• example:
  &load_fields  
      filename = "fields.saved",  
      factor = 1.5;  
  &end

  This loads fields from the file fields.saved, applying a factor of 1.5 to the values. These fields become the only time-varying fields in the problem. (Others may be superimposed in subsequent operations.)

• synopsis and defaults:
  #namelist load_fields  
      STRING filename = NULL;  
      double Ez_peak = 0;  
      double factor = 1;  
      double time_threshold = 0;  
      long overlay = 0;  
  #end

• details:
  • filename: Name of the file from which to take field data. Normally created with the save_fields command. The file is in SDDS-protocol, typically with multiple data pages. Normally, the first page is used. This may be modified with the time_threshold parameter.
  • Ez_peak: Desired maximum value of on-axis longitudinal electric field. The fields from the data file are scaled to obtain this value. Note that this option cannot be used if TM fields are disabled. By default, no scaling occurs.
  • factor: Factor by which to multiply the fields before use. If Ez_peak is 0, then this value is ignored. One of factor or Ez_peak must be nonzero.
  • time_threshold: Minimum simulation time, in seconds, at which the fields may have been created in order to be used. For example, if time_threshold is 1e-9, then spiffe will advance through the pages of fields until it finds one from 1ps or more (in simulation time) after the start of the simulation that created the file filename.
  • overlay: Normally, the time-varying fields in the simulation are set equal to those in the file, within a scale factor. If you wish to simply add the new fields to those already in force, then set overlay to a nonzero value.