Sample Problem: Cylindrical Halfraum at NIF

Setting Laser Beam Parameters

In this example, we set the beam parameters as follows:

• Point the beams 500 microns outside the LEH (measured along the halfraum axis) .
• Set the focus such that the focus point of each beam is 300 microns from the axis, toward the laser ports.
• Set all beams powers to 2.5 TW.

It is often useful to group the beams in each problem into clusters. For this problem, we set all beams of quads Q46T and Q46B into a cluster called "Beams_Q46". To do this,

• Select Lasers | Add Cluster. Give the name "Beams_Q46".
• Select beams from Quad Q46B (beams A, B, C, D) and Quad Q46T. With all 8 beams highlighted, use the right mouse button, and select Move To Cluster | Beams_Q46. (This can also be accomplished using the menu: Lasers | Move To Cluster | Beams_Q46.)

To set the beam power for all drive beams:

• Right-click on cluster "Beams_Q46", and select Set Powers.
• Set the power to 2.5 TW. This represents the total power in the blue, green, and red cones for NIF.

To point the beams:

• Right-click on cluster "Beams_Q46", and select Set Pointing.
• For reference coordinate system, select: "Halfraum_transparent_LEH_1" (the halfraum's one and only LEH).
• The coordinate system axes for the LEH can be viewed by selecting Show | Axes | Halfraum_transparent_LEH_1.
• Set the position of the Reference Point for Beam Pointing to: r = (0, 0, 0.05) cm. This points the beams to a spot 500 microns outside the LEH.
• Set the Focus point offset to -0.03 cm. This move to focus point (of the NIF blue cone) 300 microns along a line from the Reference Point for Beam Pointing toward the laser beam port.

All laser beams are now set up. The image below shows the halfraum, the 8 drive beams from quads Q46T and Q46B, and the axes for the LEH coordinate system (red, green, blue line segments represent x-, y-, and z-axes, respectively).