1. a general exercise showing the creation of an input file

7/28/2019 1. a General Exercise Showing the Creation of an Input File

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1.0 Example: Create Simple Geometries Using the VisualEditor

This section will contain step by step instructions for creating an input file using the VisualEditor. For this example, a cube within a sphere will be created. Figure 1-1 displays the

finished geometry.

Figure 1-1 Final Result of Geometry Creation Example.


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Start the Visual Editor.

Use Windows Explorer to bring up the Visual Editor. Figure 1-2shows a view of the initial

screen. Notice that the main menu functions are shown across the top and that each plot windowhas its own set of plot commands.

Figure 1-2 Startup Configuration for the Visual Editor


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Figure 1-3 Creating the Sphere Surface

Creating a Sphere

On the Visual Editor Main Menu, clickon Surface. This will open the Surface Panel. Figure

1-3shows the result.

On the Surface Panel, note that the Surface Type is the default type which is a sphere centered at

the origin (so).

Type 50 in the 1st

Coefficient Box (the Radius).

Click on Register on the Cell Panel Menu.


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Figure 1-4 Display of Created Spherical Surface

The Visual Editor will display a large red circle once Register is selected. Surfaces are red in theVisual Editor if they are not currently assigned to a cell. Figure 1-4shows the circle displayedon both plots.

Creating the Planes

To create the cube inside the sphere, six plane surfaces must be created. Specifically, two px,

two py, and two pz planes. A px plane is a plane normal to the X axis, intersecting it at a point

on the axis. Similarly, a py plane is a plane normal to the Y axis and a pz plane is a plane normalto the Z axis.

On the Surface Panel Menu Bar, click on SurfacePlanepx. Figure 1-4 illustrates this step.

On the Surface Panel, Type 20 in the first coefficient box (as indicated inFigure 1-5)Clickon Register.


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Figure 1-5 Sphere and First px Plane

Create the other planes.

Type -20 (note that it is negative 20) in the first coefficient box to set the distance D.

Click Register

Click on SurfacePlanepy.

Click on Register. (using the previous value of -20)

Type 20 (note that it is positive 20) in the first coefficient box to set the distance D.

Click on Register.

Click on SurfacePlanepz.

Click on Register. (using the previous value of -20)

Type -20 (note that it is negative 20) in the first coefficient box to set the distance D.

Click on Register.


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Figure 1-6 Sphere and Six Plane Surfaces shows the result.

Figure 1-6 Sphere and Six Plane Surfaces

Click Close to close the Surface Panel.


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Figure 1-7 Selecting First Surface in Creation of Cube Cell

Create the Cube Cell

A cell is defined by selecting surfaces to bound a region and then choosing a point that is entirelyinside or entirely outside all the surfacesto set the sense for the surfaces.

On the Main Menu, Click on Cell to open the Cell Panel.

On the Left Plot Window, Drag the mouse across Surface 2 as indicated by the dashed line in

Figure 1-7. Notice that the line showing Surface 2 becomes blue once it has been selected.

Drag across the other three plane surfaces on the Left Plot window.


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Figure 1-8 Using Both Plot Windows to Select Cube Surfaces

To specify a cube, six surfaces must be specified. Only four surfaces are visible from the Left

Plot window. It is necessary to use the Right Plot window to specify the py surfaces. Figure 1-8illustrates this concept.

Drag across the two py surfaces in the Right Plot Window as indicated by the dashed lines in

Figure 1-8.

A point must be selected to indicate whether the cell will be inside these surfaces or outside

them. For more information, see the discussion withFigure 1-13 Defining the Point to

Determine Cell Sense.

Click in the center of the square on either Plot Window.

In the message box on the cell panel, it should say Point Accepted.


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Figure 1-9 Define Point, Paste and Register

Once a region has been defined, it may be either added (with Paste) to the area that will be

included in the cell or subtracted (with Cut) from it. In this case, the region that has beendefined will be added to the cell so Paste is the correct choice.

Click Paste on the Cell Panel menu to add this region to the cell definition.

Click Register on the Cell Panel menu to create the cell.

Figure 1-10shows the cube cell as Cell 1.

Click the Cell Number toggle to turn on Cell Numbers (as indicated inFigure 1-10)

The lines on the square turn green when pasted and then return to red when registered. They are

still red because a cell exists inside the surfaces but not outside them.


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Figure 1-10 Display of Cube Cell.

Create the Outside World

All space must be defined in a valid MCNP geometry so there must always be an OutsideWorld. In this case, the outside world is all the space outside the sphere.

Drag across the sphere surface.

Click INSIDE the sphere as indicated inFigure 1-11. For more information, see the discussion

withFigure 1-13 Defining the Point to Determine Cell Sense.


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Figure 1-11 Create Sphere Cell

The outside world will consist of all area that is not inside the sphere. This may be defined by

pasting all the area outside the sphere or by cutting out the area within the sphere. In thiscase, the area within the sphere will be cut out.

Click Cut.

Click Register.

Figure 1-12 Cube Cell and Outside Worldshows the result.


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Figure 1-12 Cube Cell and Outside World

Defining the Point to Determine Cell Sense.

When creating cells, the point determines the cell sense. When the bounding surface is a

sphere, defining the point within the center of the sphere means that the cell will include the areainside the sphere. Similarly, if the point is defined by clicking a location outside the sphere, the

cell will include the area outside the sphere (but not inside).

While this is fairly obvious for spheres, it is more complex with planes forming shapes such as a

cube.

InFigure 1-13, choosing Point 1 can specify the inside of the sphere. It does NOT specify the

outside of the cube. Point 1 specifies an area that is:

Right of Surface 2,Below Surface 6,Above Surface 7, and

Right of Surface 3.

Choosing Point 1 causes the sense (direction) of Surface 3 to incorrectly be defined as right of

surface 3.


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Figure 1-13 Defining the Point to Determine Cell Sense

Similarly, Point 2 can specify the inside of the sphere. It does NOT specify the outside of the

cube. Choosing Point 2 to define the outside of the cube incorrectly causes the sense of

Surface 6 to be defines as below surface 6.

Point 3 can define the inside of the cube or the inside of the sphere.

Point 4 can define the outside of the sphere but NOT the outside of the cube.

To choose the area between the sphere and the cube, the user must first define a cell that includes

the inside of the sphere (paste) and then subtract the area inside the cube (cut).

Creating the Cell Inside the Sphere and Outside the Cube

As discussed above, this cell will be created by first creating the region inside the sphere and

then cutting out the region inside the cube.


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Figure 1-14 Paste Inner Sphere

Drag the mouse across the sphere surface to select it.

Click inside the sphere (it does not matter whether it is inside the cube or not).

Click Paste on the Cell Panel.

This will paste the interior of the sphere into the cell definition.


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Figure 1-15 Cut Cube from Sphere

Drag the mouse across all six planes (use the right plot to get the py planes). This step isillustrated by the dashed lines inFigure 1-15.

Click inside the cube to establish the sense as inside the cube.

Click on Cut on the Cell Panel.

This will cut away the area inside the cube from the area inside the sphere.

Click on Register.

Cell three has now been created and consists of the area inside the sphere but outside the cube.


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Figure 1-16 Geometry with Three Cells Created

Figure 1-16shows the completed cells. Valid MCNP cells are shown in black.

1. a general exercise showing the creation of an input file

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