The practical bandwidth is 1-3 THz. Since KrF is a gas laser, the optical path in glass is minimized, and there is less nonlinear distortion. It was in the late 1980s, therefore, that the NRL laser fusion program shifted its effort from glass lasers to the development of a new KrF laser named Nike. The Propagation Bay is a 155-ft long insulated room. The temperature throughout can be held uniform to within a half degree Fahrenheit so that a diffraction-limited beam can propagate back and forth without distortion.
Charcoal filters eliminate the UV absorbing gases.
At each mirror array, all 56 beams can be simultaneously aligned in a few seconds by an automatic alignment system. The 60 x 60 cm2 KrF amplifier cell is pumped from two sides by identical electron beams generated from Marx banks. The large black magnetic field coils of 2-4 kG are used to guide the electron bearns through the gas cell. ISI is a fine optical system that images the uniform aperture onto the target. If the optical distortion of the system is small compared to the size of the focal spot image, then the profile shape will be only slightly distorted, when averaged over relevant hydrodynamic time scales.