Selection and suppression of soft x-ray spectral features using optimized multilayer coatings

The design of multilayer mirrors which specifically select or suppress spectral features is described. To illustrate the method, the spectra from laser-produced plasmas of carbon and aluminium are used. By using a suitable mirror the intensity of the C V He-alpha line at lambda = 4.03 nm can be reduced to 1.1 x 10(-4) of that in the C VI Ly(alpha) line at lambda = 3.37 nm, compared to 0.97 in the source emission spectrum and 1.6 x 10(-2) for a periodic multilayer. In the aluminium spectrum, two closely spaced lines at lambda = 3.505 and 3.660 nm, which have comparable emitted intensities, can be individually selected using pairs of multilayers. The reflected intensity ratios are under ten for periodic multilayers, but can be over 300 for the shorter wavelength line and almost 140 for the longer using optimized pairs of mirrors.