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.
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 ----------------------------------------------------------------------
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.
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:
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.]
Resets the field map, has the same effect as RESET FIELD-MAP.
Specifically states that the field map is not periodic in x. [This is the default.]
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.]
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.]
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.]
Specifically states that the field map is not periodic in y. [This is the default.]
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.]
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.]
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.]
Specifically states that the field map is not periodic in z. [This is the default.]
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.]
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.]
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.]
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.]
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.]
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.]
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.
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.]
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.]
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.]