Evaluation of imaging properties of soft x‐ray multilayer mirrors and their application to highly dispersive spectral imaging

A variety of normal‐incidence multilayer mirrors (MMs) intended for studies of astrophysical and laboratory soft‐x‐ray radiation sources have been synthesized on concave (r=1.6−2.0 m) fused silica substrates. The MMs range in resonance wavelength λ0 from 4.5 to 31 nm. Their imaging capability has been evaluated from small‐source imaging tests employing to a laser‐plasma broadband XUV radiation source and a high‐resolution XUV photographic film. The photographs testify to a subarcsecond angular resolution. For 17.5‐nm MMs, a resolution of at least ≊0.32 arcseconds has been demonstrated, which is only 2.4λ0/D for the MMs involved.