6.4 Curved Surface Considerations

When designing a test for a curved object, the variation in the incident laser fluence as a function of angle will result in an angular dependence of the generated impulse. If there is no (or an insignificant amount of) laser energy loss in the tamper, the incident laser fluence will scale as the cosine of the angle of incidence. Additionally, some laser light is reflected at the surface of the tamper material. The magnitude of this reflection depends on the polarization of the laser light, the tamper index of refraction, and the incident angle. On NIF DLI, each of the laser beams are linearly polarized at the target with orthogonal polarization, relative to each other (one beam is s-polarized and the other is p-polarized). An example transmission curve as a function of incidence angle for perpendicular polarization, parallel polarization, and combined (50/50) is shown in Figure 9.

 

Light transmission versus angle for index of refraction ratio of 1.0/1.33.
Figure 9. Light transmission versus angle for index of refraction ratio of 1.0/1.33.