To
investigate this, we performed a series of viewfactor calculations using VisRad. We
used a scale-1 halfraum on the P6-P7 axis
(DANTE angle of 37.4 degrees), and made
the following simplifying assumptions:
• No backlighter in the experiment
• The witness plate and the halfraum are both made of gold (maximum albedo =
0.7)
• The laser beam power is constant with a 1ns square pulse (475 J/beam for each of
15 beams).
• There is no “lip” on the halfraum (Figure
2)
• The 15 laser beams were pointed to make a single ring of laser hot spots around
the halfraum.
Some
of these simplifying assumptions are
relaxed later.
Fig. 2: Left: A
typical halfraum with a (1/4) lip over the LEH. Right: A simplified halfraum with no lip. Some surfaces in the VisRad
simulations are shown as ‘mesh’ so the viewer can see what’s behind them.
Fig. 3: view from
center of witness plate, looking out the LEH. On the
left, a more typical configuration with cone 2 and cone 3 beams pointed differently and an LEH lip included. On the right, the result of implementing the simplifying
assumptions.