Large-aperture, high-power beams such as those on NIF generally produce non-diffraction limited irradiance profiles at focus because of optical aberrations on the beams caused by the large number of optical surfaces. NIF beams produce about 150-µm spots (containing 50 percent of the beam energy) (see Figure 4-14). To limit the peak intensity and to lower the backscatter risk from targets, the focal spot is typically conditioned using continuous phase plates, smoothing by spectral dispersion, and polarization smoothing.
