Search for high-strength multilayer free-standing film filters with high transmittance in the wavelength range of the "water window" (2.3-4.4 nm)

Abstract

Some variants of the composition of multilayer absorption film filters with a high transmittance in the spectral region of the "water window" (2.3-4.4 nm) have been considered. Having created an ultimate pressure difference between the sides of free-standing films at which they are damaged, we compared the strength of 100 nm thick Ti-based multilayer filters with Al, Be, C interlayers and 100 nm thick V-based multilayer filters with Al interlayers. Sc and Cr was also considered as interlayers. Among the tested periodic multilayer structures, the best strength characteristics were demonstrated by Ti/Be (with a fraction of Ti in a period of about 0.6) and V/Al (with a fraction of V in a period of about 0.4) multilayer filters. Despite the fact that Ti/Be and V/Al filters are inferior in strength to Ti and V monolayer filters of the same thickness, these multilayer filters may be of interest, since they have either a higher transmittance in the "water window" (Ti/Be) or more high level of blocking of visible radiation (V/Al). Keywords: spectral region of the "water window" multilayer free-standing filters, ultimate pressure difference, film filter strength, transmittance in the soft x-ray, visible light blocking level.

Metrology for sub-Rayleigh-length target positioning in ∼1022 W/cm2 laser–plasma experiments

“…The operating range, 17 -25 nm, was defined by the multilayer structure optimized for maximum uniform reflectance in the 12.5 -25 nm range [73,74] and absorption cutoff at the aluminum L2,3 edge at λ ≈ 17 nm in the optical blocking filters. Imaging spectrographs of this type are used in different forms, e. g. in a combination of a MM with a transmission grating [75] or a varied line space (VLS) reflection grating [76,77] . Such XUV spectrographs have been employed in experiments on coherent soft X-ray generation via frequency upshift of the laser pulse reflected from a relativistic 'flying mirror' [78] and via the BISER mechanism [41] .…”