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Sample Problem: Cylindrical Hohlraum at OMEGA

Setting Up the Grid

This sample problem includes several features and tools in VISRAD designed to facilitate target grid setup:

In this example, we set up a hohlraum for the OMEGA target chamber with the following characteristics:

Step-by-step instructions for setting up a hohlraum target are:

The images below shows the target after all of the steps is completed. The views are set using the Set Viewing Position dialog. Left: TIM #5 view (Port H14). Center: Dante view (Port H16-I) . Right: X-TVS view.

        

 

Cylindrical Hohlraum Setup

The hohlraum cylinder will serve as the reference coordinate system for several other target components. Doing this, all of the components will stay attached to the hohlraum if its Position or Orientation Angles change.

Insert Shields Inside the Hohlraum

Add open shields on the inside of the hohlraum at the edges of where the flat sample will be located.

Backlighter Setup

Place a 0.5 mm radius disk backlighter a distance 4 mm from target chamber center (TCC) in the direction away from H14.

Cut a Diagnostic Hole in the Hohlraum Along the Line from H14 to the Center of the Backlighter

Clip the "hohlraum" such that there is a clear line-of-sight that extends from H14 (TIM #5) (i.e., a point located, say, 30 cm from TCC in the direction of H14) to the center of the "backlighter".

 

Add a Flat Rectangular Surface on the Side of the Hohlraum

Add a flat rectangular surface (of length 800 μm) on the side of the hohlraum, and position it such it is along the line of sight from the H7-H14 (TIM #5) axis. Put the flat on the H7 side.

Attach the Hohlraum to the TIM #3 (H18) Target Mount

Add a 0.03 mm radius stalk to the "hohlraum".

Attach the Backlighter to Stalk from TPS #2

Add a 0.03 mm radius stalk to the "backlighter".

 

The Target Components Reference Coordiate Systems Tree is useful in seeing how various Target Components are referenced to each other. It can be viewed using the Target | Show Ref. Coord. System Tree menu item.

 

 

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1 Setting R-Corner to 0.01 cm provides a rounded edge to the cylinder.

2 It is important to set the surface normals appropriately for radiation calculations. Surfaces have a preferred orientation, emitting/reflecting light on one side only. To emit/reflect light on both sides, either an object with non-zero thickness must be used (see Size/Grid tab of Object Parameters Dialog), or a second, nearly identical object must be set up which has surface normals facing in the opposite direction.

3 This is the centroid position of the clipping volume box. Since we will use a clipping box with a height of 0.4 mm and place the flat (rectangle) a r = 0.7 mm, the centroid of the clipping box is at r = 0.7 + 0.5*0.4 = 0.9 mm.

4 For information on setting the Polar and Azimuthal values, see Specifying Orientation Angles.

5 The value of 0.07746 = 2*sqrt( Rhohlraum 2 - Rflat 2) = 2*sqrt( 0.082 - 0.072).

 


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