BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Beam-shaping refractive optics for coherent X-ray sources DTSTART;VALUE=DATE-TIME:20200715T084000Z DTEND;VALUE=DATE-TIME:20200715T090000Z DTSTAMP;VALUE=DATE-TIME:20260416T023743Z UID:indico-contribution-1881@indico.inp.nsk.su DESCRIPTION:Speakers: Dmitry Zverev (Immanuel Kant Baltic Federal Universi ty)\nThe most advanced X-ray sources\, such as third-generation synchrotro ns and free electron lasers (XFEL)\, are capable to generate high brightne ss coherent radiation\, especially in the hard X-ray region. The availabil ity of such beams facilitates the development of a new generation of X-ray optics\, whose optical properties allow going far beyond simple collimati on and focusing functions. This optics makes it possible to form amplitude and phase of wave front with almost complete freedom\, using the most out standing properties of synchrotron and X-ray laser radiation such as brigh tness\, monochromaticity\, and coherence.\nLike in visible light optics\, beam-shaping functions can be implemented in an X-ray regime based on both diffraction and refractive optical elements. For example\, the beam-shapi ng optics based on diffraction optical elements (DOEs) allows realizing al most any complex optical transformation. However\, due to the high penetra ting power of X-rays through DOEs their use is significantly limited in th e hard energy range. In addition\, since many unknown beam parameters must be defined in advance\, the design of such beam-shaping optical elements is a challenging task. As for the beam-shaping elements based on refractiv e optics [1]\, they are deprived of the disadvantages which are inherent i n DOEs. This optics allows for some beam transformations\, and the possibi lities of its applications cover various areas of modern X-ray optics\, su ch as interferometry and coherent diffraction\, phase-contrast microscopy and imaging\, and ultrafast and nonlinear optics studies.\nFor example\, o ne of the most vibrant demonstrations of the beam-shaping optics is a spec ial class of refractive optical elements that have axial symmetry and are capable to convert a point-like source to a narrow axial straight line seg ment. These optical elements are called axicons. Recently\, we demonstrate d an X-ray parabolic refractive axicon lens as a novel type of X-ray beam- shaping element [2]. Under coherent X-ray illumination\, the parabolic axi con generates Bessel-like beam propagated along the optical axis in the ne ar field and ring-shaped beam in the far field.\nThe optical transformatio ns produced by axicon can be used in areas requiring special illumination\ , as well as extended focused beams\, for instance\, in diffraction and im aging techniques\, in metrological applications\, as well as for source di agnostics and beamline alignment. Moreover\, such beam-shaping capabilitie s can significantly simplify some existing experimental layouts or lead to completely new optical schemes for X-ray techniques based on synchrotron and XFEL sources. Most recently\, we proposed an optical scheme of phase-c ontrast microscopy technique based on the axicon optics [3]. Due to the un ique optical properties of the parabolic refractive axicon lens\, the new approach turned out to be more efficient for visualization of weakly absor bing samples as compared with the traditional microscopy technique.\nIn ad dition to new X-ray axicon refractive optics\, it is also worthwhile to co nsider other beam-shaping elements\, called interferometers\, whose optica l functions are well known and successfully used. These devices allow real izing the paraxial optical schemes of interferometry based on the coherent properties of modern X-ray sources. Recently\, we demonstrated bilens and multilens interferometers based on refractive optics which under coherent illumination generate an array of mutually coherent beams focused at some distance [4-5]. The size of the focal spots is restricted to the diffract ion limit and can be less than tens of nanometers. When the beams overlap they produce a steady interference pattern of fringes in the far field.\nT he proposed interferometers can be used in a wide X-ray energy range while maintaining high efficiency. The field of applications of their optical f unctions is not limited only to the interferometry techniques and can be e xtended in the area of beam diagnostics and beam conditioning. Moreover\, such lens systems open up new opportunities for the development of phase-c ontrast imaging technique\, which was recently demonstrated [6].\n\n[1] Sn igirev\, A.\, Kohn\, V.\, Snigireva\, I.\, & Lengeler\, B. (1996). A compo und refractive lens for focusing high-energy X-rays. Nature\, 384(6604)\, 49-51.\n[2] Zverev\, D.\, Barannikov\, A.\, Snigireva\, I.\, & Snigirev\, A. (2017). X-ray refractive parabolic axicon lens. Optics Express\, 25(23) \, 28469-28477.\n[3] Zverev\, D.\, Snigireva\, I.\, & Snigirev\, A. (2018) . X-ray Phase Contrast Microscopy Based on Parabolic Refractive Axicon Len s. Microscopy and Microanalysis\, 24(S2)\, 296-297.\n[4] Snigirev\, A.\, S nigireva\, I.\, Kohn\, V.\, Yunkin\, V.\, Kuznetsov\, S.\, Grigoriev\, M. B.\, ... & Detlefs\, C. (2009). X-ray nanointerferometer based on Si refra ctive bilenses. Physical review letters\, 103(6)\, 064801.\n[5] Snigirev\, A.\, Snigireva\, I.\, Lyubomirskiy\, M.\, Kohn\, V.\, Yunkin\, V.\, & Kuz netsov\, S. (2014). X-ray multilens interferometer based on Si refractive lenses. Optics express\, 22(21)\, 25842-25852.\n[6] Zverev D.\, Snigireva I.\, Kohn V.\, Kuznetsov S.\, Yunkin V.\, Snigirev A.\, (2020) X-ray phase -sensitive imaging using a bilens interferometer based on refractive optic s. Accepted for publication in journal Opt. Express\n\nhttps://indico.inp. nsk.su/event/24/contributions/1881/ LOCATION: Zoom 890 9721 5207 URL:https://indico.inp.nsk.su/event/24/contributions/1881/ END:VEVENT END:VCALENDAR