Sample Problem: Cylindrical Halfraum at OMEGA

Setting Up the Grid: Target Positioner (Stalk)

The target positioner, or stalk, is aligned in the direction of Port H2. For this illustration, we set the length of the stalk to 0.15 cm, and place one end of it at the mid-plane of the halfraum. To set up the stalk, perform the following steps:

• Select Target | Add Object.
• Select "Cylinder" for the target component type.
• Set the object name to "Stalk".
• In the Position tab of the Object Parameters Dialog:
• For the Reference Coordinate System, select "Halfraum".
• To determine the orientation angles for the Stalk, we need to use the Port Positions Dialog to find the angles to Port H2 in the coordinate system of the Halfraum. Showing the diagnostic ports in the Halfraum's coordinate system gives (for Port H2): polar angle = 70.53 degrees and azimuthal angle = 142.24 degrees.
• Enter these angles for the polar and azimuthal orientation angles.
• To specify the position of the stalk, it is easiest use a cylindrical coordinate system; so select "Cylindrical".
• The azimuthal angle to Port H2 is also the azimuthal angle for the position in a cylindrical geometry. So for the position, set phi to 142.24 degrees.
• A simple geometric analysis shows the the radial position of the centroid of the stalk is at: r = R + 0.5 * L * sin(theta) (R = halfraum radius, L = stalk length, theta = polar angle to Port H2). Similarly, to place one end of the stalk at the mid-plane of the halfraum, the z-position of the stalk centroid is at: z = 0.5 * L * cos(theta).
• Using R = 0.08 cm, L = 0.15 cm, and theta = 70.53 degrees gives: r = 0.1507 cm, z = 0.0250 cm. Set the r and z position variables to these values.
• In the Size/Gridding tab of the Object Parameters Dialog:
  • Set the radius to 0.001 cm.
  • Set the length to 0.15 cm.
  • Set surface normals out.
  • Use 2 grid points along the wire's z-axis, and 4 azimuthal grid points (low-resolution gridding is sufficient for the stalk).
• Select "OK".