Summary

You have to give gd1 the following information:

• what geometry you are interested in (-brick -gbor etc),
• what the boundary planes of your computational volume are (-mesh),
• what the conditions at these boundary planes are (-mesh),
• what the default mesh density shall be (-mesh),
• where gd1 shall store the result (-general),
• what kind of computation gd1 shall perform (-eigenvalues, -fdtd).

The complete inputfile up to now (doris04.gdf) is:

 #
 # Some helpful symbols:
 #
 define(EL, 1) define(MAG, 2)
 define(INF, 1000)

 #
 # We define symbols that will be used to describe our cavity:
 # The names of the symbols can be up to 32 characters long,
 #
 define(OuterRadius   , 46.23e-2/2 )
 define(InnerRadius   , 13.00e-2/2 )
 define(GapLength     , 27.60e-2   )
 define(CurveRadius   ,  0.585e-2  )
 define(BeamPipeRadius, 14.17e-2/2 )
 define(TaperLength   , 13.2e-2    )

 ###
 ### We enter the section "-general"
 ### Here we define the name of the database where the
 ### results of the computation shall be written to.
 ###    (outfile= )
 ### We also define what names shall be used for scratchfiles.
 ###     (scratchbase= )
 ###
 -general
    outfile= /tmp/UserName/doris
    scratchbase= /tmp/UserName/doris-scratch

 ###
 ### We define the borders of the computational volume,
 ### and we define the default mesh-spacing.
 ###
 -mesh
     spacing= InnerRadius/15
     pxlow= -1.1*OuterRadius
     pylow= -1.1*OuterRadius
     pzlow = -(GapLength/2+TaperLength+9e-2)
     pxhigh= 0
     pyhigh= 0
     pzhigh= 0

     #
     # The conditions to use at the borders of the computational volume:
     #
     cxlow= electric, cxhigh= magnetic
     cylow= electric, cyhigh= magnetic
     czlow= electric, czhigh= electric
 ########
 #
 # We fill the universe with metal
 #
 -brick
     material= EL
     xlow= -INF, xhigh= INF
     ylow= -INF, yhigh= INF
     zlow= -INF, zhigh= INF
     doit
 
 #
 # we carve out the body of the cavity
 #

 -gbor
    material= 0
    origin= (0,0,0)
    zprimedirection= (0,0,1)
    rprimedirection= (1,0,0)
    range= (0,360)

    clear      # clear any old polygon-description
      # point= (z,r)
    point= ( -(GapLength/2+TaperLength+10e-2), 0              ) # p1
    point= ( -(GapLength/2+TaperLength+10e-2), BeamPipeRadius )
    point= ( -(GapLength/2+TaperLength      ), BeamPipeRadius )
    point= ( -(GapLength/2+CurveRadius      ), InnerRadius    )
      arc, radius= CurveRadius, size= small, type= counterclockwise
    point= ( -(GapLength/2                  ), InnerRadius+CurveRadius )
    point= ( -(GapLength/2                  ), OuterRadius    )
     ## crossing z=0 plane
    point= (  (GapLength/2                  ), OuterRadius    )
    point= (  (GapLength/2                  ), InnerRadius+CurveRadius )
      arc, radius= CurveRadius, size= small, type= counterclockwise
    point= (  (GapLength/2+CurveRadius      ), InnerRadius    )
    point= (  (GapLength/2+TaperLength      ), BeamPipeRadius )
    point= (  (GapLength/2+TaperLength+10e-2), BeamPipeRadius )
    point= (  (GapLength/2+TaperLength+10e-2), 0              )
 show= now
 doit

   -mesh
      #
      # enforce two meshplanes, at the bottom and the top of the cavity:
      #
      zfixed(2, -GapLength/2, GapLength/2 )
 -volumeplot
##    doit

 -eigenvalues
    solutions= 15
    estimation= 10e9   # the estimated highest frequency
    doit