Fresnel zone

About: Fresnel zone is a research topic. Over the lifetime, 2337 publications have been published within this topic receiving 37650 citations.

Computer Simulation of Fresnel Diffraction from Triple Apertures by Iterative Fresnel Integrals Method

Abstract: Computer Simulation of Fresnel Diffraction from Triple Apertures by Iterative Fresnel Integrals MethodThe Iterative Fresnel Integrals Method (IFIM) has been applied for the simulation and generation of the complete near-field Fresnel diffraction images created by triple apertures for the first time. The simulation can be performed in any PC using an included MATLAB program. Necessary formalism has been derived and simulation algorithm has been developed for this application. An interesting combination of interference effects with Fresnel diffraction has been observed in the simulation images. Transition to the expected Fraunhofer diffraction pattern from Fresnel diffraction for triple apertures is also observed by the simulations. The program can serve as a useful tool to study the complex phenomenon of Fresnel diffraction from triple apertures.

Processing of high-resolution, deep-tow marine seismic data

Abstract: Conventional near‐surface seismic systems provide limited resolution of ocean bottom sedimentary horizons. This problem is related to the size of the Fresnel zone and is particularly important in deep water or topographically rugged regions. The French Institute for Marine Research and Exploitation (IFREMER) has recently investigated methods to overcome this limitation.

Characterization of a two-channel, high resolution hard x-ray microscope using Fresnel zone plates for laser-plasma interaction experiments

Abstract: New X-ray imaging techniques are currently being developed at the "Commissariat a l'energie atomique et aux energies alternatives" in the context of Inertial Confinement Fusion. Fresnel zone plates (FZPs) are being considered as they can perform high-resolution and high-flux imaging in the X-ray domain. Here we present the characterization of a bi-lens FZPs resolution used in an imager prototype, designed for the LULI2000 laser facility. Characterization was performed on a synchrotron radiation facility and on a femtosecond laser facility. The resolution of the two FZP channels was measured to be between 2.4 μm and 5.2 μm and the expected total resolution for the diagnostic was to be 3.3 μm.

Achromatic x-ray focusing using diffractive and refractive elements

Abstract: We develop a new type of X-ray lens system which is achromatic in a limited energy range. For such achromatswe combine dierent types of refractive and diractive e lements. For example, Fresnel zone plates and planarparabolic concave SU-8 lenses are comb ined with lenses with a biconvex parabolic shape and with Fresnel lenses,respectively. We present numerical re sults from a theoretical study of such optical systems. We determine thefocal spot size for an energy range of about E ± E with E/E 17%. Amongst other results we “nd that,compared with conventional lens systems, the spot siz e can be reduced by several tens of percent by using suchachromatic lens systems.Keywords: achromats, compound refractive lenses, CRL, X-ray, zone plates, numerical simulation 1. INTRODUCTION The development of third generation s ynchrotron sources and the improvem ent in micro-system technologies,have simultaneously provoked great advances in X-ray micro-focusing. For many applications of X-rays such asX-ray spectroscopy, dir action, small angle scattering, and imaging, focusing is an issue of primary importancein order to study small objects or to spatially resolve and distinguish all kinds of structures. Thus, in thelast decades dierent chromatic opti cal devices for monochromatic X-rays have been developed using dierentmaterials and various micro-fabrication techniques. Such optical systems are by now successfully working, evenin the hard X-ray range, but they are chromatic. If the same optical device is used for a dieren t energy, theresulting focal length diers, i.e., chromatic aberration occurs. Consequ ently for focusing devices, the focalspot size increases up to several tens of microns for a broad energy band, whereas it can be smaller than onemicron for a discrete energy or a suciently narrow energy band. For the improvement of micro-focus lensesdierent physical phenomena are being used, depending on the “eld of application. For instance, mirrors, whichare especially used in astronomy, as they need a relatively wide working distance, and capillaries, which areprimarily used for illumination, are both based on total re”ection. Fresnel zone plates, which are based ondir action, are widespread in astronomy and synchrotron applications. Compound refractive lenses (CRL),which utilize refraction, are applicable in a notably large energy range (5keV-500keV). In particular they areused for microscopy and spectroscopy purposes. CRL which are used in the hard X-ray range and Fresnel zoneplates require a highly monochromatic beam. Since sever al applications require a variety of X-ray energies oreven tunability, a search for achromatic optical devices has started. Such applications include, e.g. , absorptionspectroscopy, which requires an energy scan within a de“ned energy range, or pink beam applications, such asselective ”uorescence spectrosc opy or anomalous diraction.In the following two alternatives for achromatic X-ray lenses are proposed, which are based on dir action andrefraction. The results of numerical simulations are also presented, which have been performed for an in-depthstudy of the potential performance.

Figure Metrology for X-Ray Focusing Mirrors with Fresnel Holograms and Photon Sieves

Abstract: We report on interferometric measurements of the figure error of an ultra-precise mirror with the shape of an elliptical toroid for the diffraction limited focusing of hard x-rays from an undulator x-ray source. We describe measurement configurations using Fresnel type holograms and photon sieves, and evaluate the measurement uncertainty.