&CELL: FIELD-MAP


FILES

  The set of files to be read in. The files can contain the mesh
  or maps of

  - the potential
  - the electric E-field
  - the electric D-field (used to compute epsilon)
  - the weighting field
  - the magnetic field
  - the dielectric constant

  All maps must share the same grid.

  The weighting field is the electric field that results from
  placing one electrode at 1 V and earthing all others. This
  field is used to compute the signals induced on the electrode
  at 1 V, by moving charges.

contents

  One may specify the contents of the file before the name. Doing so
  is mandatory if the file contains the weighting field. Although the
  mesh files do not have to be identified as such, this is recommended.
  The contents is optional for all other types of data written by
  Maxwell. A warning is issued if the file contains other data than
  the declared contents.

  Currently, the following contents types are recognised:

  ----------------------------------------------------------------------
  Name                        Used to compute
  ----------------------------------------------------------------------
  B-FIELD (=MAGNETIC-FIELD)   Drift lines
  ELECTRIC-FIELD              Drift lines, various other plots
  D-FIELD                     Epsilon by comparing E and D
  MATERIAL (=D-FIELD)         Drift line termination
  MESH                        Always needed with Maxwell Field Simulator
  POTENTIAL (=VOLTAGE)        Contour maps
  WEIGHTING-FIELD             Induced signals
  ----------------------------------------------------------------------

label

  Serves to identify the solids with which the weighting field is
  associated. In other words, the field map has been computed by
  setting the potential of the associated conducting solids to 1 V
  and the potential of all other conductors to 0 V.

  The label is a single character and should match one or more of
  the LABEL's used in the listing of the SOLID's.

  A label is mandatory for the weighting field. No label should be
  specified for other maps than the weighting field.

format

  Specifies the program that has been used to generate the field
  maps. Currently, the following formats are accepted:

  - Maxwell Parameter Extractor 2D, by Ansoft
  - Maxwell Parameter Extractor 3D, by Ansoft
  - Maxwell Field Simulator, by Ansoft

  All formats are recognised automatically, and a format doesn't
  have to be specified therefore.

  Recipes for creating field maps with these programs are given
  in the sub-topics.

Additional Information on:

  • PARAMETER-EXTRACTOR-2D
  • PARAMETER-EXTRACTOR-3D
  • FIELD-SIMULATOR-3D

  • DRIFT-MEDIUM

      If you provide a map of the dielectric constants, or both a map
      of D and a map of E, you have the possibility to specify which
      of the materials is the drift medium.
    
      There are 3 ways to select the drift medium:
    
      - via an integer: this is interpreted as a sequence number in
        the sorted list (from small to large) of dielectric constants
      - via real: this is interpreted as a dielectric constant
        divided by eps0 (i.e. gasses typically have a value close
        to 1), the list of dielectric constants present in the field
        map is searched for the nearest match
      - via a keyword such as SMALLEST.
    
      Beware: DRIFT-MEDIUM 3 is not the same as DRIFT-MEDIUM 3.0 !
      In the first case, the medium with the 3rd dielectric constant
      will be selected. In the second case, the medium with the
      dielectric constant closest to 3 will be taken.
    
      [By default, the medium with the lowest dielectric constant is
      assumed to be the drift medium.]
    

    RESET

      Resets the field map, has the same effect as RESET FIELD-MAP.
    

    NOT-X-PERIODIC

      Specifically states that the field map is not periodic in x.
    
      [This is the default.]
    

    X-PERIODIC

      States that the field map has an x-periodicity.
    
      The length of one period is taken to be the maximum extent
      in x of the field map.
    
      A cell can have only one of the symmetry types X-PERIODIC,
      X-MIRROR-PERIODIC and X-AXIALLY-PERIODIC.
    
      [By default, a field map is not assumed to be periodic.]
    

    X-MIRROR-PERIODIC

      States that only half of the cell has been entered and that
      there is a mirror image on both sides. In addition, the cell
      has a periodicity, equal to twice the maximum extent in x of
      the field map.
    
      A cell can have only one of the symmetry types X-PERIODIC,
      X-MIRROR-PERIODIC and X-AXIALLY-PERIODIC.
    
      [By default, a field map is not assumed to be periodic.]
    

    X-AXIALLY-PERIODIC

      States that the cell has an axial periodicity around the
      x-axis and that only one period is represented in the field
      map.
    
      The length of one period is deduced from the field map, and
      is therefore not specified on the FIELD-MAP statement.
    
      The symmetry axis must pass through y=z=0.
    
      A cell can have only one of the symmetry types X-PERIODIC,
      X-MIRROR-PERIODIC and X-AXIALLY-PERIODIC.
    
      [By default, a field map is not assumed to be periodic.]
    

    NOT-Y-PERIODIC

      Specifically states that the field map is not periodic in y.
    
      [This is the default.]
    

    Y-PERIODIC

      States that the field map has an y-periodicity.
    
      The length of one period is taken to be the maximum extent
      in y of the field map.
    
      A cell can have only one of the symmetry types Y-PERIODIC,
      Y-MIRROR-PERIODIC and Y-AXIALLY-PERIODIC.
    
      [By default, a field map is not assumed to be periodic.]
    

    Y-MIRROR-PERIODIC

      States that only half of the cell has been entered and that
      there is a mirror image on both sides. In addition, the cell
      has a periodicity, equal to twice the maximum extent in y of
      the field map.
    
      A cell can have only one of the symmetry types Y-PERIODIC,
      Y-MIRROR-PERIODIC and Y-AXIALLY-PERIODIC.
    
      [By default, a field map is not assumed to be periodic.]
    

    Y-AXIALLY-PERIODIC

      States that the cell has an axial periodicity around the
      y-axis and that only one period is represented in the field
      map.
    
      The length of one period is deduced from the field map, and
      is therefore not specified on the FIELD-MAP statement.
    
      The symmetry axis must pass through x=z=0.
    
      A cell can have only one of the symmetry types Y-PERIODIC,
      Y-MIRROR-PERIODIC and Y-AXIALLY-PERIODIC.
    
      [By default, a field map is not assumed to be periodic.]
    

    NOT-Z-PERIODIC

      Specifically states that the field map is not periodic in z.
    
      [This is the default.]
    

    Z-PERIODIC

      States that the field map has a z-periodicity.
    
      The length of one period is taken to be the maximum extent
      in z of the field map.
    
      A cell can have only one of the symmetry types Z-PERIODIC,
      Z-MIRROR-PERIODIC and Z-AXIALLY-PERIODIC.
    
      [By default, a field map is not assumed to be periodic.]
    

    Z-MIRROR-PERIODIC

      States that only half of the cell has been entered and that
      there is a mirror image on both sides. In addition, the cell
      has a periodicity, equal to twice the maximum extent in z of
      the field map.
    
      A cell can have only one of the symmetry types Z-PERIODIC,
      Z-MIRROR-PERIODIC and Z-AXIALLY-PERIODIC.
    
      [By default, a field map is not assumed to be periodic.]
    

    Z-AXIALLY-PERIODIC

      States that the cell has an axial periodicity around the
      z-axis and that only one period is represented in the field
      map.
    
      The length of one period is deduced from the field map, and
      is therefore not specified on the FIELD-MAP statement.
    
      The symmetry axis must pass through x=y=0.
    
      A cell can have only one of the symmetry types Z-PERIODIC,
      Z-MIRROR-PERIODIC and Z-AXIALLY-PERIODIC.
    
      [By default, a field map is not assumed to be periodic.]
    

    LINEAR

      Requests linear interpolation of all fields within each triangle
      or each tetrahedron. This leads to interpolated fields that are
      continuous, but have a discontinuous first derivatives at the
      boundaries between the triangles/tetrahedrons.
    
      This method can be applied to all field maps.
    
      [By default, the highest order method permitted by the field
      map will be used.]
    

    QUADRATIC

      Requests quadratic interpolation of the fields within each triangle
      or each tetrahedron. The interpolation is done using normalised
      Lagrange polynomials in terms of the triangular coordinates. This
      ensures that the field on triangle/tetrahedron boundaries depends
      only on the field values of the nodes located on the boundary.
      Therefore, the interpolated fields are continuous, but the first
      derivative is in general not continuous across boundaries between
      adjacent triangles/tetrahedrons.
    
      This method can only be applied to field maps with additional
      nodes halfway the vertices. This information is present in for
      instance all Maxwell field maps.
    
      [By default, the highest order method permitted by the field
      map will be used.]
    

    CUBIC

      Requests cubic interpolation of the fields within each triangle
      or each tetrahedron. The interpolation is done using normalised
      Lagrange polynomials in terms of the triangular coordinates. This
      ensures that the field on triangle/tetrahedron boundaries depends
      only on the field values of the nodes located on the boundary.
      Therefore, the interpolated fields are continuous, but the first
      derivative is in general not continuous across boundaries between
      adjacent triangles/tetrahedrons.
    
      This method can only be applied to field maps with additional
      nodes at 1 third and at 2 thirds between the vertices. There
      are currently no field map formats with which this interpolation
      order can be used.
    
      [By default, the highest order method permitted by the field
      map will be used.]
    

    WINDOW

      The WINDOW keyword is used to eliminate triangles or tetrahedrons
      from the mesh.
    
      A triangle or a tetrahedron is eliminated whenever one of its
      vertices is located outside the window.
    

    Z-RANGE

      Every cell needs, for Garfield, to have a default extent
      in all 3 dimensions. When the cell contains only wires and
      planes, then the extent in z is derived from the length of
      the wires. When instead, a 2-dimensional field map is used,
      there is no way to know the z-extent of the cell.
    
      This argument is ignored if the field map is 3-dimensional.
    
      [By default, the cell is assumed to go from -50 cm to +50 cm
      in the z-direction.]
    

    PLOT-MAP

      Requests the materials to be shown in plots of the chamber.
    
      The option has effect only if material properties have been
      entered, either as a map of dielectric constants or as maps
      of both D and E.
    
      The material with the smallest dielectric constant is shown
      with representation MATERIAL-1. The medium with the next highest
      dielectric constant with MATERIAL-2 etc. The drift medium is
      never shown.
    
      Field maps do not (at the moment) cover areas filled with
      conducting material since there is no field inside these.
      To visualise these, one has to enter them manually with the
      SOLIDS command. SOLIDS doesn't interfere with PLOT-MAP.
    
      [By default, the map is shown.]
    

    HISTOGRAM-MAP

      Requests histograms to be plotted of the aspect ratio (i.e. the
      ratio of the largest and the smallest vertex separation within a
      tetrahedron or triangle) and of the surface or volume of the
      tetrahedrons or triangles in the mesh that is read.
    
      Tetrahedrons and triangles with large aspect ratios can be a sign
      that the mesh is of poor quality. When using Maxwell, one should
      consider adding dummy volumes which constrain the mesh elements
      (contact CERN Maxwell support or Ansoft for further information).
    
      Tetrahedrons with a very large volume and triangles with a very
      large surface are likely to cause problems while drifting particles
      since the E field inside is linear, without guaranteed match with
      neighbouring elements.
    
      [These histograms are not made by default.]
    

    Keyword index. Formatted on 10/11/98.