Abstract
The technology to focus hard-X-rays (photon energy larger than 1–2 keV) has made great progress in the past three years. The progress was particularly spectacular for lenses based on the Fresnel zone plate concept. The spatial resolution notably increased by a factor of three, opening up entirely new domains of application, specifically in biomedical research. As we shall see, this evolution is the result of a painstaking optimization of many different aspects rather than of a single technical breakthrough.
Highlights
Solving the nanofabrication and stability problems is the key issue in the technology of Fresnel zone plates (FZPs) for hard-X-rays
Pattern at the stage of Figure 5(f). This “broken-line” design markedly improves the mechanical stability compensating the problems caused by the high aspect ratio
The coated wire is “sliced” (e) by ion beam sectioning producing precise and thick FZP with the desired aspect ratio. Different variations of this multicoating approach were applied to the fabrication of FZPs both for soft-X-rays and hard-X-rays [11,12]
Summary
The technical evolution of zone plate devices for hard X-rays dramatically accelerated in the past two years [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29]. Assuming equal width for adjacent transmitting and absorbing zones, rm equals the difference between the values given by Equation (2) for n = m and n = m − 1, i.e., This result has fundamental implications on the FZP technology. In his pioneering article of 1974, Kirz [34] injected realism into the analysis by considering actual fabrication materials with their specific and values in the X-ray range He found that with a suitable choice of materials and a suitable design (in particular, the zone thickness) the ideal efficiency can be increased up to 40%, essentially by decreasing the power lost to absorption and to the zero-order beam. Solving the nanofabrication and stability problems is the key issue in the technology of FZPs for hard-X-rays
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