Grazing incidence metal mirrors (GIMMs) have been examined to replace dielectric mirrors for the final ele ments in a laser beam line for an inertia! confinement fusion reactor. For a laser driver with a wavelength from 250 to 500 nm in a 10-ns pulse, irradiated mirrors made of Al, Al alloys, or Mg were found to have calcu lated laser damage limits of 0.3-2.3 J/cm 3 of beam en-erg}' and neutron lifetime fluence limits of over 5 x 10 w 14 MeV n/cm 2 {or 2.4 full power years when used in a 1,000-MW reactor) when used at grazing incidence (an angle of incidence of 85 degrees) and operated at room temperature or at 77 K. A final focusing system including mirrors made of Al alloy 7475 at room tem perature or at liquid nitrogen temperatures used with a driver which delivers 5 MJ of beam energy in 32 beams would require 32 mirrors of roughly 10 m 3 each. This paper briefly reviews the methods used in calculating the damage limits for GIMMs and discusses critical is sues relevant to the integrity and lifetime of such mirrors in a reactor environment.

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