-fdtd: Compute time dependent fields

This section enables the branching to subsections that only make sense for time domain computations. The "doit" in this section also starts the time domain computation.

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 # Flags: nomenu, noprompt, nomessage,                                        #
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 # section: -fdtd                                                             #
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 # -ports                     -- absorbing boundary conditions                #
 # -pexcitation               -- excited port mode                            #
 # -lcharges                  -- one or more relativistic line charges        #
 # -windowwake                -- Wakes in a moving mesh window                #
 # -clouds          -- not yet finished.                                      #
 # -linitialfields            -- loads initial fields at t=0                  #
 # -voltages                  -- enforce voltages between points              #
 # -decaytime                 -- z-dependent damping.                         #
 # -time                      -- timestep etc.                                #
 # -storefieldsat             -- when to store fields                         #
 # -fexport                   -- when to store fields                         #
 # -smonitor                  -- what scalar quantities to store              #
 #                                                                            #
 # compressed= yes            -- minimal RAM and CPU time, more swapspace     #
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 # doit, ?, return, help                                                      #
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• -ports:
  Branches to the sub-section -fdtd/-ports where you specify the location of "ports" and some properties of these ports.
• -pexcitation:
  Branches to the sub-section -fdtd/-pexcitation, where you specify the center frequency, the bandwidth and the amplitudes of selected modes of selected ports.
• -lcharge:
  Branches to the sub-section -fdtd/-lcharge, where you specify the properties of relativistic line charges.
• -windowwake:
  Branches to the sub-section -fdtd/-windowwake, where you specify the properties of a moving mesh window to compute the wakepotential of relativistic line charges.
• -clouds:
  Branches to the sub-section -fdtd/-clouds, where you specify the properties of a non-relativistic charge clouds. As of today (October 2004), the implementation of this 'Particle in Cell' computation is not yet fully finished. Please contact Warner Bruns, if you need it badly.
• -linitialfields:
  Branches to the sub-section -fdtd/-linitialfields, where you specify what fields shall be the initialfields of a time dependent computation.
• -voltages:
  Branches to the sub-section -fdtd/-voltages, where you specify excited voltages between arbitrary points. As of today (October 2004), the implementation of this excitation is not yet fully finished. Please contact Warner Bruns, if you need it badly. item -decaytime:
  Allows z-dependent damping of the fields without specifying a graded lossy dielectric.
• -time:
  Branches to the sub-section -fdtd/-time, where you specify the minimum and maximum allowed simulation time.
  You can also specify the times where the electric and magnetic fields are written.
• -storefieldsat:
  Branches to the sub-section -fdtd/-storefieldsat. You can specify multiple time-ranges where the electric and/ or magnetic fields are stored to files.
• -fexport:
  Allows writing of selected field parts as ASCII files during the time domain computation. Useful for making movies.
• -smonitor:
  Branches to the sub-section -fdtd/-smonitor, where you specify what scalar quantities shall be monitored during the time domain computation. As of today (October 2004), the implementation of this is not yet fully finished. Please contact Warner Bruns, if you need it badly.
• doit:
  If you say "doit", the settings in "-general, -mesh, -material" are checked, the mesh is (re-)generated, and the iteration for the time dependent fields is performed.
  While the field computation is running, the amplitudes of selected port modes are written, and selected electric and magnetic fields are written. If a wake computation is performed, the data required for the computation of wakepotentials is also written. These amplitudes and fields (and wake-data) can be processed further by gd1.pp. After the field computation, the program stops.