&CELL: FIELD-MAP: FILES: format

PARAMETER-EXTRACTOR-2D

To generate your field maps with Maxwell Parameter Extractor 2D, you may wish to follow this recipe:

1. Go through the various steps until "Solve Parameters", taking care (before drawing anything) to adjust in "Draw Cross Section" the "Model Drawing Size" such that it fits exactly the area of your detector - do not leave any empty space around it. Then enter "View Fields" from where you perform the following steps:
2. Click on "calc", select "plane", if the upper area is not empty then click on "clear". Do also a "smooth" and a "push" to ensure the mesh is the same for all maps. Then click on "voltage" and do an ASCII "write" to a file ("write" is in the second set of commands to which you access via "next", to get back to the first set click on "prev"). Maxwell appends the string ".arg" to the file name you enter. This creates a map of the potential.
3. Repeat step 2 with "E_vector" instead of "voltage", choose a file name different from the one used in step\ 2. This creates a file that contains both Ex and Ey.
4. Depending on the Solver that you use:
   • In "Electrostatic" mode: click again on "calc", select again "plane", do a "clear" if needed. Click on "E_vector", then on "vec_cons", fill in 1\ 0\ 0 as vector, click on "execute", click on "Materials", click on "epsilon", ensure that multiplication is set to "yes" and "execute", then click on "scalar_x" and do an ASCII "write" of the result. Choose a file name different from those used in steps\ 2 and 3. This procedure leads to a file that contains the dielectric constant.
   • If you model you chamber in "DC conduction mode", then apply the same recipe with "epsilon" replaced by "sigma".
5. If you do not wish to compute signals, you are ready at this point. Otherwise, go back to the "Parameter Extractor" main menu, click on "Setup Boundaries/Sources", and select "Define", confirm that you wish to "Modify" and then adjust the voltages of all electrodes such that the electrode that you wish to read out is at 1\ V and all other electrodes at 0\ V. Then "Exit", confirming that you wish to save the modifications.
6. Go to the "Setup Solution Parameters" in the Parameter Extractor, click on "Capacitance", select "Current" as Starting Mesh, suppress "Adaptive Analysis". This ensures that the field is calculated on the same mesh as the field calculated in point\ 1.
7. Write out the electric field as described in step 2, choosing a file name different from the names chosen in steps\ 2, 3 and 4. This generates the weighting field. Repeat from step\ 5, if you intend to read out more than one electrode.

These steps should lead to a set files with names that end on .arg and that are located in the es.pjt sub-directory of your project.

Be sure to create the E, V, \ε or \σ and weighting field maps with identical meshes and the E, V and \εor \σ maps with identical boundary conditions.

The names of these 4 files should be placed after the FILES keyword of the FIELD-MAP command, the name of the weighting field maps should be preceded by the keyword "WEIGHTING-FIELD" to distinguish it from the regular electric field map. The order is not important. There is no need to specify that the files come from Maxwell Parameter Extractor 2D.

Maxwell documentation at CERN can be found in http://wwwinfo.cern.ch/ce/ae/Maxwell/documentation.html

(Instructions from Pawel Majewski)

FIELD-SIMULATOR-2D

To generate your field maps with Maxwell\ 2D Field Simulator, you may like to follow the following recipe:

1. Go through the various steps until "Solve". Then enter "Post Process" for the "nominal problem" where you click on "calc", select "Plane" and, if the upper area is not empty click on "clear".
2. Click on "voltage" and do an ASCII "write" to a file ("write" is in the second set of commands to which you access via "next", to get back to the first set click on "prev"). Choose a file name like "V", Maxwell automatically appends the string ".arg" to the file name you enter. This creates a map of the potential.
3. Repeat step\ 2 with "E_Vector" instead of "voltage", choose a file name different from the one used in step 2. This creates a file that contains both Ex and Ey.
4. If you wish Garfield to know about the materials present in the chamber, then either:
   • Repeat step\ 2 with "D_Vector" instead of "voltage", choosing a file name different from those in steps 2 and 3. This creates a file with a field map of D. The dielectric constant is computed by Comparing D and E.
   • Do a "clear", then click on "E_Vector", then on "vec_cons", fill in 1\ 0\ 0 as vector, click on "Execute", click on "Materials", click on "epsilon", ensure that multiplication is set to "Yes" and "Execute", then click on "scalar_x" and do an ASCII "write" of the result. Choose a file name different from those used in steps\ 2 and 3. This procedure creates to a file that contains the dielectric constant.
   • If you model you chamber in "DC conduction" mode, then apply the above recipe with "epsilon" replaced by "sigma".
5. If you do not wish to perform signal calculations, you're ready at this point. Otherwise go back to the "2D Field Simulator" main menu, enter "Setup Boundaries/Sources", confirm that you wish to "Modify" and then adjust the voltages of all electrodes such that the electrode that you wish to read out is at 1\ V and all other electrodes at 0\ V. Then "Exit", confirming that you wish to save the modifications.
6. Go to the "Setup Solution" in the main menu, select "Options", select "Current" as Starting Mesh, suppress "Adaptive Analysis" and click "OK". Next go to "Solve" in the main menu and select "Nominal Problem". These steps compute the weighting field on the same mesh as the field calculated in point\ 1.
7. Write out the electric field as described in step\ 2, choosing a file name different from the names chosen in steps\ 2, 3 and 4. This generates the weighting field map. Repeat from step\ 5 if you intend to read more than one electrode.

These steps should lead to a set of files with names that end on .arg and that are located in your project directory.

Be sure to create the E, V, D, \ε or \σ and weighting field maps with identical meshes and in addition the E, V and D maps with identical boundary conditions.

The names of these 4 files should be placed after the FILES keyword of the FIELD-MAP command, the name of the weighting field maps should be preceded by the keyword "WEIGHTING-FIELD" to distinguish it from the regular electric field map. The order is not important. There is no need to specify that the files come from Maxwell 2D Field Simulator.

Information about using Maxwell at CERN can be found in http://wwwinfo.cern.ch/ce/ae/Maxwell/Maxwell.html

PARAMETER-EXTRACTOR-3D

When generating your field maps with this program, you may wish to follow this recipe:

1. Go through the various steps until "Solve Parameters", taking care (before drawing anything) to adjust in "Draw Cross Section" the "Model Drawing Size" such that it fits exactly the area of your detector - do not leave any empty space around it. Then enter "View Fields" where you click on "calc", select "space" and, if the upper area is not empty click on "clear".
2. Click on "phi", do a "push" to ensure the mesh is the same for all maps and then "smooth" the potential map. Do an ASCII "write" to a file. Maxwell automatically appends the string ".arg" to the file name you enter, it is therefore sufficient to enter for instance just "V". This creates a map of the potential.
3. Repeat step 2. for "E_vector" and "D_vector", without doing a "push", and writing to files with different names. Creating the D field map is optional.
4. You may also wish to create weighting field maps as described for Maxwell Parameter Extractor 2D.

This procedure should create maps of the electrostatic potential, the E field, the D field and perhaps of a weighting field. The dielectric constants are computed by comparing E and D. These files will be located in the efs3d.pjt sub-directory of your project.

Be sure to create the E, V, D and weighting field maps with identical meshes and the E, V and D maps with identical boundary conditions.

Information about using Maxwell at CERN can be found in http://wwwinfo.cern.ch/ce/ae/Maxwell/Maxwell.html

FIELD-SIMULATOR-3D

Beware that files produced with Maxwell Version\ 11 can be read with the interface for earlier versions, and vice-versa, but the results will be incorrect. Be sure therefore to specify the correct Maxwell version on the FIELD-MAP command line.

When you use this program to create your field maps, you have to provide the following to Garfield:

1. The mesh: The mesh is contained in a .hyd and a .pnt file stored in the project directory (and not in an "efs3d.pjt" sub-directory of the project directory). When using the DELETE-BACKGROUND option, the project .shd file is needed in addition. The files have names like "fileset2", "fileset1", "current", "efs3d", "previous" and "initial".
   • If you do not specify a mesh file explicitly, then Garfield will look in the directory of the first field map for mesh files with the above names, starting from "fileset2".

   • To select a mesh manually, you provide the name of the .pnt, .hyd or .shd file (complete file name) and either place this name first in the list of files to be read, or identify it explicitly as containing a mesh by prefixing the MESH keyword.

2. The field maps of V, D and E written out in .reg format. With Maxwell\ 3D Field Simulator, there is no need to smooth the field maps, as opposed to Maxwell\ 3D Parameter Extractor.

   The field maps can be created as follows: After having gone through the various steps, in the "Post Process" menu, select "Nominal Problem". From the "Data" menu, select "Calculator". In the "Input" column select the "Qty" menu where you pick "phi". In the "Output" column select "Write\ ..." and write out the field to a file called, for instance, "V.reg". Repeat the same steps replacing "phi" by "E" and "D".

3. Optionally, you may also provide weighting fields. Weighting fields are electric fields that are obtained by setting the potential of all conductors to 0\ V except the read-out conductor which is set to 1\ V.

Be sure to create the E, V, D and weighting field maps with identical meshes and the E, V and D maps in addition with identical boundary conditions.

Information about using Maxwell at CERN can be found in http://wwwinfo.cern.ch/ce/ae/Maxwell/Maxwell.html

MAXWELL-2D-SV

After having worked your way through the various steps from model definition till problem solving, click on "Post\ Process\ ..." and enter "Data/Calculator". Then:

1. Click on "Qty"
2. Select "phi" to create a map of the potential
3. Click on "Write ..."
4. Enter a name for the file (the extension *.reg will be appended automatically to the file name.)

Alternatively, the electric field can be derived from the potential by selecting the COMPUTE-ELECTRIC-FIELD option. Several users have reported problems with the electric field maps as exported by Maxwell and this approach can therefore be recommended.

When using Maxwell SV, you have to feed the following files to Garfield:

• The mesh files preceded by the contents indication MESH. Maxwell SV, contrary to earlier 2D versions of Maxwell, does not insert mesh information in the field maps. Garfield extracts the mesh structure from 2 files: a list of triangles (which has an extension of .tri) that contains pointers to a file with a list of mesh coordinates (extension .pts). Garfield will automatically read these files if they are located in the same directory as the field maps and have a file name of "fileset1" or of "fileset2". You may move these 2 files elsewhere and change their names, provided that they are given the same file name, that the extensions are unchanged and that the 2 files are placed in the same directory. You then also have to inform Garfield of the directory and file name by specifying one (and only one) of these files - the extension doesn't matter since Garfield fills it in itself.
• The model file preceded by the contents indication MODEL. The extension of this file is .sm2 and the file name is usually the same as the project name. Maxwell SV, like some other Ansoft programs, solves the problem in normalised mesh coordinates and the mesh files do not contain information regarding the problem domain. Garfield extracts the dimensions of the problem domain from the model file. The problem domain is set to the square region (-1,-1) to (1,1) in case the model file isn't read.
• The field maps, optionally preceded by a keyword to indicate the contents.
• You may in addition supply weighting fields. Weighting fields are computed as electric fields but the potential of all conductors should be set to 0 except the read-out conductor which is set to 1. Be sure to create the E, V, D and weighting field maps with identical meshes. This is achieved by first solving for E, V and D, then disabling mesh refinements when solving for the weighting fields. The E, V and D maps should in addition have identical boundary conditions.

An axis of rotational symmetry, if any, should be detected automatically and result in the Z-ROTATIONALLY-SYMMETRIC option being switched on.

(Procedure from Pawel Majewski.)

TOSCA

1. use OPERA version\ 7.0.
   • create the directory $VFDIR/opera/3d/util
   • copy in this directory the Makefile and the program util.f which can be found in http://consult.cern.ch/writeup/garfield/examples/tosca
   • run in the same directory the command "$VFDIR/install/makeprog $VFDIR"

2. Generate the geometrical mesh with the 3d Opera preprocessor.

3. Click on "MESH" and then choose the "quadrilaters" option.

4. Click again on "MESH" and choose the "Volume\ mesh\ ...\ Mesh\ *" option.

5. Click on "FILE" and choose the "write node table" option in order to create the "username.table" file that contains the mesh node coordinates.

6. Generate, clicking again on "FILE", the usual username.OP3 file ready to be analysed by TOSCA.

7. Run the Fortran program "util" with the command: $VFDIR/opera/3d/util > "username1.table" and, after pushing the "return" button, typing "username.op3" on the keyboard and pushing "return" again. The file "username1.table" includes now a table that describes each element of the mesh, specifying the nodes that make it up.

8. Run TOSCA.

9. Run the 3d\ Opera post-processor. Load the TOSCA result. Click on "FIELDS" and choose the "table of field points" sub-menu. In this sub-menu:
   1. Select "input from file" and give "username.table" (see item\ 6 above) as input.
   2. Choose an "username2.table" as output according to your taste
   3. Click on "output components options" and define:
      • Component 1 = X
      • Component 2 = Y
      • Component 3 = Z
      • Component 4 = Ex
      • Component 5 = Ey
      • Component 6 = Ez
      • Component 7 = Dx
      • Component 8 = Dy
      • Component 9 = Dz
      • Component 10 = V
   4. Click the "process table" option that will describe, for each mesh node, the value of the electric field and potential.

The files "username1.table" and "username2.table" (see item\ 6 and 10 above) are now ready for Garfield.

A Garfield input file that uses "username.table" and "username1.table" can be found in http://consult.cern.ch/writeup/garfield/examples/tosca/example

A single Tosca generated map can contain various kinds of data, such as the potential, the electric field and the D field. Since the file contains a description of the data, the contents field should only make clear that the file is not a mesh file. One can therefore set the contents field on the FIELD-MAP command to be any of the contained items.

It is advisable to use the INTERPOLATE-ELECTRIC-FIELD option when using Tosca field maps.

(Recipe from Guido Maria Urciuoli, INFN Gruppo Collegata Sanitá, Viale Regina Elena 299, 00161 Roma, Italia.)

TOSCA-118

The Tosca file, called a "simulation database" in Tosca-speak, should contain at least the following Tosca "datasets":

• 164: units
• 2412: mesh structure
• 2411: node location
• 2414: potential solution

After the model has been created in the Modeller, create the simulation database with

• 'element type' = quadratic and
• 'surface element type' = curved:

To achieve this, enter at the console:

SOLVERS PROGRAM=&VF_ANALYSISTYPE& -SOLVENOW OPTION=NEW
        ELEMENT=QUADRATIC SURFACE=CURVED FILE='YourFileName.op3';

Model \→ Create Analysis Database...

In the post-processor export the results to an I-DEAS Universal File, where it important is to set BASIS=ELEMENT, i.e. write values at every node of every element:

As a console command:

IDEAS FILE='YourFileName.unv' MODE=CREATE TYPE=REAL
      BASIS=ELEMENT FIELD=SCALAR COMP=V;

Tables \→ SDRC I-DEAS Unv File...

(Recipe provided by Konstantin Klementiev <kklementiev@cells.es>.)

COMSOL-2D-LINEAR

These elements have only 3 nodes, the potential is linear within each element and the local gradient is constant.

Although such field maps can be read, their use is not recommended. Use instead COMSOL-2D-QUADRATIC.

COMSOL-2D-QUADRATIC

For the recipe to write such field maps, please refer to COMSOL-3D-QUADRATIC.

Garfield doesn't recognise this format automatically, be sure therefore to specify that your field map is in COMSOL-2D-QUADRATIC format.

You may specify a distance unit for such field maps, centimetres are assumed if no unit is given.

Example:

&CELL
field-map files potential "COMSOLFIELD2D.txt" ...
                weighting-field "COMSOLFIELD2DElectrode1.txt" label s ...
        comsol-2d

&FIELD
plot-field contour v

&SIGNAL
select s
plot-field vector

COMSOL-3D-LINEAR

These elements have only 4 nodes, the potential is linear within each element and the local gradient is constant.

Although such field maps can be read, their use is not recommended. Use instead COMSOL-3D-QUADRATIC.

COMSOL-3D-QUADRATIC

Garfield doesn't recognise this format automatically, be sure therefore to specify that your field map is in COMSOL-3D format.

You may specify a distance unit for such field maps, centimetres are assumed if no unit is given.

First, solve your problem in COMSOL. Take care to select 2nd order Lagrange elements. Then export the field map as follows:

1. Go to menu File \&rarr; Export \&rarr; Post-Processing Data
2. Set path/filename to export, e.g. "exported.txt"
3. Choose file format "Nodes, elements, data"
4. Check that under the "Subdomain" tab "Electric Potential" is selected as Expression to export
5. Click "OK" to write the file

To import the file in Garfield:

1. Go to cell section (&CELL).
2. Import the exported file using the FIELD-MAP command, this may take quite some time depending on the size of the map.
3. Garfield does not recognise this format automatically, hence be sure to specify that your field map is in COMSOL-3D format.
4. If you get a warning stating that the number of tetrahedrons exceeds the compilation limit, then recompile Garfield with a larger value for MXMAP. Alternatively, check the quality of the mesh - large field maps frequently result from poorly refined field maps. These not only slow down all calculations performed with them, they also are of poor numeric quality. You may also wish to consider using virtual volumes surrounding tiny electrodes.
5. To save time next time you need the field map, you may wish to write a binary copy using SAVE-FIELD-MAP.

Example:

&CELL
field-map files "exported.txt" comsol-3d
save-field-map "exported.bin"

(Recipe written by Jeremy Janney <JJanneySG@hotmail.com> and Sven Lotze <lotze@physik.rwth-aachen.de>.)

ANSYS-PLANE-121

ANSYS will occasionally generate degenerate quadrilaterals, which are curved quadratic triangles.

The recipe assumes that the command format is used. Most of the commands cited can of course also be run from the GUI.

1. Clear earlier calculations and enter the pre-processor:

   FINISH
   /CLEAR,START
   /PREP7
   

2. If using the GUI, enter the preferences and ensure that the only discipline selected within the "Electromagnetic" group is "Electric". The equivalent commands are:

   KEYW,PR_ELMAG,1
   KEYW,MAGELC,1
   

   Disable the p-method solution options. This option leads to elements of higher polynomial order, which are a priori preferred, but Garfield does not yet have shape functions for these.

   /PMETH,OFF,1
   

3. Select the quadrilateral as element:

   ET,1,PLANE121
   

   In case your chamber has rotational symmetry around an axis, a non-default element behaviour needs to be selected:

   ET,1,PLANE121   ! Select plane quadrilaterals
   KEYOPT,1,3,1    ! Declare the element to be axisymmetric
   

   In ANSYS, the y-axis acts as axis of rotational symmetry and no part of the model should be located in x\&nbsp;\&lt;\&nbsp;0. When reading the field map with Garfield, you have to declare the symmetry again using X-ROTATIONALLY-SYMMETRIC, Y-ROTATIONALLY-SYMMETRIC or Z-ROTATIONALLY-SYMMETRIC.
4. When defining material properties, be sure that every material has its permittivity set. Choose material numbers starting from 1 and leave no holes in the numbering. Set the permittivity of conductors to a very high value. Set the resistivity of perfect conductors to 0 so as to make them eligible for removal as background (see the DELETE-BACKGROUND option). Try to avoid temperature-dependent properties as these can not be used by Garfield to identify materials. If you need to use them, then do not write out the MPLIST file (see below).

   For instance, to define a perfect conductor (material\&nbsp;1) and a dielectricum (material\&nbsp;2):

   MP, PERX, 1, 1e10 ! Metal
   MP, RSVX, 1, 0.0
   MP, PERX, 2, 4.5  ! Bulk dielectric constant
   

5. Create the model. See any of the numerous ANSYS tutorials for advice. Pay particular particular attention to gluing adjacent areas where necessary (AGLUE command). For instance, to create a conducting strip on the wall of a block of dielectric material:

   ! Define some dimensions, in microns
   halfpitch = 50
   thickbulk = 200
   halfstrip = 20
   thickstrip = 5
   
   BLC4, 0, 0, halfpitch, thickbulk   ! Area 1: dielectricum
   BLC4, 0, 0, halfstrip, thickstrip  ! Area 2: conductor
   ASBA, 1, 2, , , KEEP               ! Area 1 becomes area 3
   
   AGLUE, ALL                         ! Glue everything
   

6. Assign material properties with the AATT command:

   ASEL, S, , , 3             ! Select the dielectricum
   AATT, 2                    ! Properties of material 2
   ASEL, S, , , 2             ! Select the conductor
   AATT, 1                    ! Properties of material 1
   

7. Set boundary conditions:

   ASEL, S, , , 2             ! Select the metal
   LSLA, S                    ! Select all its border lines
   DL, ALL, 2, VOLT, 1000     ! Set the borders to 1000 V
   
   ASEL, S, , , 3             ! Select the dielectricum
   LSLA, S                    ! Select all its border lines
   LSEL, R, LOC, Y, thickbulk ! Sub-select lines at y=thickbulk
   DL, ALL, 3, VOLT, 0        ! Set this line to 0 V
   
   ASEL, S, , , 3
   LSLA, S
   LSEL, R, LOC, X, 0         ! Select the lines at x=0
   DL, ALL, 3, SYMM           ! Impose a symmetry condition
   ASEL, S, , , 3
   LSLA, S
   LSEL, R, LOC, X, halfpitch ! Idem for y=halfpitch
   DL, ALL, 3, SYMM
   

8. Mesh the problem. This can for instance be done using free meshing:

   LSEL,ALL
   ASEL, ALL
   MSHKEY,0
   SMRT, 3
   AMESH, 2,3
   

   It is not always necessary to mesh the metal parts of the device. Then solve the problem:

   /SOLU
   SOLVE
   FINISH
   

   Optionally visualise the solution:

   /POST1
   /EFACET,1
   PLNSOL, VOLT,, 0
   

9. Write the solution to files. The potentials at the nodes are written to a file with the PRNSOL command. In the example below, the file name is chosen to be "PRNSOL.lis" but feel free to use another name. It is the name of this file which must follow the FILES keyword.

   /OUTPUT, PRNSOL, lis
   PRNSOL
   /OUTPUT
   

   There is no need to write the electric field to a file since the COMPUTE-ELECTRIC-FIELD option is implied when using ANSYS.

   The PRNSOL file contains the potentials at the nodes. When interpolating between nodes, Garfield needs to know where each of these nodes is located in space. This information is contained in the output of the NLIST command, which should be written to a file called "NLIST.lis". Note the COORD option - without this option, the file would contain additional information which is not used in Garfield, at the price of reduced precision in the node coordinates. Garfield can read files in either format - but the COORD option is recommended.

   /OUTPUT, NLIST, lis
   NLIST,,,,COORD
   /OUTPUT
   

   Garfield also needs to know how the nodes are tied into elements. This structure is shown by the ELIST command, of which the output has to be written to a file called "ELIST.lis":

   /OUTPUT, ELIST, lis
   ELIST
   /OUTPUT
   

   Optionally, you may transmit the dielectric constants (permittivities) and the electric resistivities to Garfield. Only write this file if your material properties do not have a temperature dependence. The commands for writing the "MPLIST.lis" file are as follows:

   /OUTPUT, MPLIST, lis
   MPLIST
   /OUTPUT
   

   If you produce the field maps on operating systems like Windows, control-M will be appended to each line. These need to be removed before the field maps can be read with Garfield.
10. Make Garfield read the field maps. You only need to specify the potential map. The remaining files, ELIST.lis, NLIST.lis and MPLIST.lis are searched for in the same directory. An example follows.

    Since ANSYS allows the user to use any consistent system of units, the real size of the device can not be found in the field map files. The user therefore has to specify the distance UNIT.

    &CELL
    field-map files "../scratch0/PRNSOL.lis" ansys-plane-121 ...
       x-mirror-periodic unit micron
    
    &FIELD
    area -0.0100 0 0.0100 0.0200
    plot-field cont v
    

In order to compute signals, Garfield needs weighting fields. Refer to the ANSYS-solid-123 recipe.

ANSYS-SOLID-123

The recipe assumes that the command format is used. Most of the commands cited can of course also be run from the GUI.

1. Clear earlier calculations and enter the pre-processor:

   FINISH
   /CLEAR,START
   /PREP7
   

2. If using the GUI, enter the preferences and ensure that the only discipline selected is "Electric" within "Electromagnetic":

   KEYW,PR_ELMAG,1
   KEYW,MAGELC,1
   

   Disable the p-method solution options. This option leads to elements of higher polynomial order, which are a priori preferred, but Garfield does not yet have shape functions for these.

   /PMETH,OFF,1
   

3. Select the 2nd\&nbsp;order tetrahedron as element:

   ET,1,SOLID123
   

4. When defining material properties, be sure that every material has its permittivity set. Choose material numbers starting from 1 and leave no holes in the numbering. Set the permittivity of conductors to a very high value. Set the resistivity of perfect conductors to 0 so as to make them eligible for removal as background (see the DELETE-BACKGROUND option). Try to avoid temperature-dependent properties as these can not be used by Garfield to identify materials. If you need to use them, then do not write out the MPLIST file (see below).

   For instance, to define a perfect conductor (material\&nbsp;1), a gas (material 2) and a dielectricum (material\&nbsp;3):

   MP,PERX,1,1e10  ! Metal
   MP,RSVX,1,0     !
   MP,PERX,2,1     ! Gas
   MP,PERX,3,4.5   ! Dielectricum
   

5. Create the model. See any of the numerous ANSYS tutorials for advice. Pay particular particular attention to gluing adjacent volumes where necessary (VGLUE command).
6. Assign material properties with the VATT command.
7. Set boundary conditions. To set for instance the voltage on all surface areas of volume\&nbsp;2 (assumed to be a conductor) to 100\&nbsp;V:

   VSEL, S, VOLU, , 2 ! Select volume 2
   ASLV, S            ! Select all areas belonging to the selected volumes
   DA, ALL, VOLT, 100 ! Set a voltage boundary on all selected areas
   

   Similarly, a symmetry boundary on all selected areas can be set with the command:

   DA, ALL, SYMM
   

8. Mesh the problem. This can be done in numerous manners. For instance, to have a fine mesh, using free meshing, in volumes 1, 2, 3 and 15:

   SMRT, 2
   MSHKEY,0
   VMESH, 1, 3
   VMESH, 15
   

   It is not always necessary to mesh the metal parts of the device. Then solve the problem:

   /SOLU
   SOLVE
   

   Optionally visualise the solution:

   /POST1
   /EFACET,1
   PLNSOL, VOLT,, 0
   

9. Write the solution to files. The potentials at the nodes are written to a file with the PRNSOL command. In the example below, the file name is chosen to be "PRNSOL.lis" but feel free to use another name. It is the name of this file which must follow the FILES keyword.

   /OUTPUT, PRNSOL, lis
   PRNSOL
   /OUTPUT
   

   There is no need to write the electric field to a file since the COMPUTE-ELECTRIC-FIELD option is implied when using ANSYS.

   The PRNSOL file contains the potentials at the nodes. When interpolating between nodes, Garfield needs to know where each of these nodes is located in space. This information is contained in the output of the NLIST command, which should be written to a file called "NLIST.lis". Note the COORD option - without this option, the file would contain additional information which is not used in Garfield, at the price of reduced precision in the node coordinates. Garfield can read files in either format - but the COORD option is recommended.

   /OUTPUT, NLIST, lis
   NLIST,,,,COORD
   /OUTPUT
   

   Garfield also needs to know how the nodes are tied into elements. This structure is shown by the ELIST command, of which the output has to be written to a file called "ELIST.lis":

   /OUTPUT, ELIST, lis
   ELIST
   /OUTPUT
   

   Optionally, you may transmit the dielectric constants (permittivities) and the electric resistivities to Garfield. Only write this file if your material properties do not have a temperature dependence. The commands for writing the "MPLIST.lis" file are as follows:

   /OUTPUT, MPLIST, lis
   MPLIST
   /OUTPUT
   

   If you produce the field maps on operating systems like Windows, control-M will be appended to each line. These need to be removed before the field maps can be read with Garfield.
10. Make Garfield read the field maps. You only need to specify the potential map. The remaining files, ELIST.lis, NLIST.lis and MPLIST.lis are searched for in the same directory. An example follows.

    Since ANSYS allows the user to use any consistent system of units, the real size of the device can not be found in the field map files. The user therefore has to specify the distance UNIT.

    field-map files "PRNSOL.lis" units=mm ansys-solid-123
    

In order to compute signals, Garfield needs weighting fields. These are obtained by setting the read-out electrodes to a potential of\&nbsp;1 and all other electrodes to a potential of\&nbsp;0.

Garfield requires the weighting fields and the main field map to share one and the same mesh. To achieve this, follow the above recipe until the end, then clear the existing loads (LSCLEAR), apply new loads and solve without meshing again. This is illustrated in the following example of 3\&nbsp;strips:

FINISH
/CLEAR,START
/PREP7
! No polynomial elements
/PMETH,OFF,1
 
! Set electric preferences
KEYW,PR_ELMAG,1
KEYW,MAGELC,1
 
! Select element
ET,1,SOLID123
 
! Material properties
MP,PERX,1,1e10  ! Metal
MP,RSVX,1,0.0   !
MP,PERX,2,1.0   ! Gas
MP,PERX,3,4.0   ! Permittivity of FR4
 
! Construct the structure
metal = 0.2
gas = 2
sub = -1
BLOCK, -10, -5, -10, 10,     0, metal ! 1: Wide side strip
BLOCK,  -2, -4, -10, 10,     0, metal ! 2: First signal
BLOCK,  -1,  1, -10, 10,     0, metal ! 3: 2nd signal
BLOCK,   2,  4, -10, 10,     0, metal ! 4: 3rd signal
BLOCK,   5, 10, -10, 10,     0, metal ! 5: Wide side strip
BLOCK, -10, 10, -10, 10,   sub,     0 ! 6: Substrate
BLOCK, -10, 10, -10, 10,     0,   gas ! 7: Gas
 
! Subtract the strips from the gas
VSBV,  7, 1, , , KEEP   ! 7 \→ 8
VSBV,  8, 2, , , KEEP   ! 8 \→ 7
VSBV,  7, 3, , , KEEP   ! 7 \→ 8
VSBV,  8, 4, , , KEEP   ! 8 \→ 7
VSBV,  7, 5, , , KEEP   ! 7 \→ 8
 
! Glue everything together 1 = left wide, 2, 3, 4, 5 = wide, 7 = sub, 8 = gas
VGLUE, ALL
 
! Assign material attributes
VSEL, S, VOLU, , 1, 5 ! Metal strips
VATT, 1, ,1
VSEL, S, VOLU, , 7    ! Gas volume
VATT, 3, ,1
VSEL, S, VOLU, , 8    ! Substrate
VATT, 2, ,1
 
! Voltage boundary conditions on the metal
VSEL, S, VOLU, , 1, 5 ! All strips at ground
ASLV, S
DA, ALL, VOLT, 0
ASEL, S, LOC, Z, gas  ! Drift electrode
DA, ALL, VOLT, -1000
ASEL, S, LOC, Z, sub  ! Back plane
DA, ALL, VOLT, 0
 
! Meshing options
VSEL, S, VOLU, , 8    ! Only mesh the gas
ASLV, S
 
MSHKEY,0
SMRT, 4
VMESH, 1,8
 
! Solve the field
/SOLU
SOLVE
 
! Write the solution
/POST1
/OUTPUT, field, lis
PRNSOL
/OUTPUT
 
! Change to weighting field boundary conditions for first narrow strip
/SOLU
LSCLEAR,ALL
 
VSEL, S, VOLU, , 1
VSEL, A, VOLU, , 3, 5
ASLV, S
DA, ALL, VOLT, 0
 
VSEL, S, VOLU, , 2
ASLV, S
DA, ALL, VOLT, 1
 
ASEL, S, LOC, Z, gas
DA, ALL, VOLT, 0
ASEL, S, LOC, Z, sub
DA, ALL, VOLT, 0
 
! Meshing options
VSEL, S, VOLU, , 1, 8
ASLV, S
 
! Solve the field
SOLVE
 
! Write the solution
/POST1
/OUTPUT, weight1, lis
PRNSOL
/OUTPUT
 
! Change to weighting field boundary conditions for 2nd narrow strip
/SOLU
LSCLEAR,ALL
 
VSEL, S, VOLU, , 1, 2
VSEL, A, VOLU, , 4, 5
ASLV, S
DA, ALL, VOLT, 0
 
VSEL, S, VOLU, , 3
ASLV, S
DA, ALL, VOLT, 1
 
ASEL, S, LOC, Z, gas
DA, ALL, VOLT, 0
ASEL, S, LOC, Z, sub
DA, ALL, VOLT, 0
 
! Meshing options
VSEL, S, VOLU, , 1, 8
ASLV, S
 
! Solve the field
SOLVE
 
! Write the solution
/POST1
/OUTPUT, weight2, lis
PRNSOL
/OUTPUT
 
! Change to weighting field boundary conditions for last narrow strip
/SOLU
LSCLEAR,ALL
 
VSEL, S, VOLU, , 1, 3
VSEL, A, VOLU, , 5
ASLV, S
DA, ALL, VOLT, 0
 
VSEL, S, VOLU, , 4
ASLV, S
DA, ALL, VOLT, 1
 
ASEL, S, LOC, Z, gas
DA, ALL, VOLT, 0
ASEL, S, LOC, Z, sub
DA, ALL, VOLT, 0
 
! Meshing options
VSEL, S, VOLU, , 1, 8
ASLV, S
 
! Solve the field
SOLVE
 
! Write the solution
/POST1
/OUTPUT, weight3, lis
PRNSOL
/OUTPUT
 
! Write the mesh to files
/OUTPUT, NLIST, lis
NLIST,,,,COORD
/OUTPUT
 
/OUTPUT, ELIST, lis
ELIST
/OUTPUT
 
/OUTPUT, MPLIST, lis
MPLIST
/OUTPUT
 
! Show the solution
/EFACET,1
PLNSOL, VOLT,, 0

After processing this, the following files should have been created:

• field.lis: the main field map with ordinary potentials,
• weight1.lis, weight2.lis, weight3.lis: weighting fields for each of the 3 read-out strips,
• NLIST.lis: the list of node coordinates,
• MPLIST.lis: the material properties,
• ELIST.lis: the mesh structure.

These files can be processed in Garfield with the following commands:

&CELL
Global bin `strips.bin`
If exist(bin) Then                // Read binary if it exists
   read-field-map {bin}
Else
   field-map files potential "~/scratch0/field.lis" ...
                   weighting-field "~/scratch0/weight1.lis" label a ...
                   weighting-field "~/scratch0/weight2.lis" label b ...
                   weighting-field "~/scratch0/weight3.lis" label c ...
             units=cm ...
             ansys-solid-123
   save-field-map {bin}           // Otherwise, create a binary
Endif
 
&GAS
arg-50-eth-50                     // For demonstration only ...
 
&SIGNAL
area -5 -10 -2  5 10 8 x-z
window 0 0.0005                   // Sample signals every 0.5 nsec
select a b c                      // Read out all electrodes
 
grid 50                           // Improve granularity
plot-field vect ewx, ewy, ewz     // Plot the weighting fields
 
Call plot_drift_area
Call drift_electron_3(-2, 0, 1.8) // Drift one electron
Call plot_drift_line
Call add_signals
Call plot_end
 
plot-signals                      // Show signals

QUICKFIELD

Please refer to http://www.quickfield.com/demo/manual.pdf

MAXWELL-11

The recipe for making such field maps is similar to that for earlier versions like Field-Simulator-3D, with the exception that the solids file (with extension .shd) will be called "fields.shd", independent of the mesh iteration and it will be located in a different directory.

Beware that files produced with Maxwell Version\&nbsp;11 can be read with the interface for earlier versions, and vice-versa, but the results will be incorrect. Be sure therefore to specify the correct Maxwell version on the FIELD-MAP command line.

Use of the DELETE-BACKGROUND option is mandatory with this format.

Formatted on 21/01/18 at 16:55.