A two-crystal X-ray interferometer

Zeitschrift für Physik A Hadrons and nuclei - The construction and successful operation of an X-ray interferometer consisting of twoseparate crystals is described. Alignment is made with the...     

A three-beam case X-ray interferometer

A new type of X-ray interferometer is described in which total reflection is established in the process of beam splitting, beam deflection and beam recombination by making essential use of simultaneous Bragg case diffraction from two different sets of net planes.The amplitudes of the interfering beams are calculated along the lines of the dynamical theory of X-ray diffraction. It is found that in the general non-planar three-beam case a complicated interaction of polarization states occurs which results in a destruction of interference contrast. On the other hand, in the planar case the polarization states stay separated and interference contrast can reach 100%.A monolithic interferometer using coplanar (440) and (404) reflections was made from a perfect silicon crystal and operated successfully. The degree of interference contrast was investigated experimentally with NiK radiation of an ordinary X-ray tube and with synchrotron X-rays from DESY.Focusing requirements and source properties influencing the coherence conditions are discussed.Part of doctorate thesis (University of Dortmund, 1976)     

High-resolution,quasi-Fabry—Perot X-ray interferometer

An extremely simple X-ray interferometer is described that should provide resolutions (λ/Δλ) of more than 10⁵. It relies on the use of nonlocalized, quasi-Fabry—Pérot interference fringes, which are detectable when a widely divergent beam of X-rays from a point source is incident on a good quality crystal. The crystal has to have a suitable lattice spacing, and in the basic method described, must not exceed a certain thickness (or coherence length).     

X-ray interferometer based on fresnel zone plates

A new type of X-ray interferometer based on three multilevel zone plates with common lens axis is suggested. Like to well-known triple Laue-case X-ray interferometer this interferometer does not impose strict requirements on the spatial and time coherence of the incident wave and therefore can be used with laboratory X-ray sources. The interferometer has advantages in the area of phase-contrast X-ray imaging connected with the image magnification.     

Eikonal approximation in the theory of X-ray interferometer

On the basis of eikonal approximation a theory of X-ray moiré formation is presented in the case where deformations are present in all three plates of the interferometer. The role of each plate of the interferometer in the process of moiré formation is revealed. The theory can be applied for the general case of weak deformations.     

An X-ray interferometer with Bragg case beam splitting and beam recombination

A new type of X-ray interferometer which uses Bragg case transmission for beam splitting and for beam recombination is described. The principles and special problems of this interferometer are discussed and a strict plane-wave treatment of the interference phenomena is presented. The feasibility of such a device is demonstrated by some interference patterns, obtained with an instrument made from a silicon crystal for use with copperKα radiation and the 220 Bragg reflection. Since, for the operation of the Bragg case interferometer, strong absorption is not essential, such devices may also be more suitable than the previously reported Laue case interferometer^1,2 for use with neutrons.     

X-ray phase contrast imaging based on three-block multilevel zone plate interferometer

A new scheme of X-ray phase contrast imaging, based on the previously suggested three-block interferometer composed by multilevel Fresnel zone plates, is considered. Two significant features, namely, image optical magnification and low requirements on the spatial and temporal coherency of incident radiation are combined in this scheme.     

Two-dimensional interferogram of an exploding selenium foil using asoft X-ray laser interferometer

We have developed a soft X-ray interferometer capable of probing large high-density plasmas with micron spatial resolutions. A neon-like yttrium X-ray laser operating at 155 Å was combined with the Mach-Zehnder interferometer to obtain electron density profiles of a laser-produced exploding selenium foil plasma. The plasma was produced with one Nova laser beam using a 120-μm line focus, the same conditions used to create a selenium X-ray laser. The interferogram of the selenium plasma was obtained from an end-on perspective     

The quantum stellar interferometer

In this paper we propose a new interferometric scheme using photon entanglement. The two main limitations of stellar interferometry are (a) the small sensitivity and (b) the need for long delay-lines to compensate the path difference between the telescopes during observing runs. Entangled-photon pairs, generated by spontaneous parametric down-conversion, open the way to measuring quantum states correlation in the near infrared between two spatially separated telescopes and at very high sensitivities (down to a few stellar photons), thanks to a new interferometric layout which does not make use of complex long delay-lines. A femtosecond laser coupled to a nonlinear crystal is used as a local oscillator to perform the double homodyne measurements. This new quantum interferometer allows to measure astronomical objet sizes with very high angular resolution down to μas level.     

The use of defocussed position of a Ronchi grating for evaluating the refractive index of lens

This report describes a Ronchi-grating shearing interferometric collimation method for determining the refractive index of a lens. A new formula has been deduced for the refractive index of the lens, which is independent of lens parameters. This newly developed device has two lenses. One of them collimates the light from a point source while the other acts as a decollimator. The point source acting as a test target is situated in the front focal plane of the collimator. The test lens is placed inside a glass cell in the back focal plane of the collimator. The Ronchi grating is exactly placed in the back focal plane of the decollimator, and a fringe-free space is observed in the common region. When the test lens is immersed in a liquid cell, it disturbs the focal point and hence interference fringes are observed. The combined system consisting of the test lens and the decollimator is moved to bring the focal point on the Ronchi grating. Thus, the difference between the two settings gives the amount of defocusing.     

Using a plane wave approximation in simulation of radiation distribution in an X-ray Talbot interferometer

This study is devoted to the analysis of the plane-wave approximation applicability to X-ray radiation incident on an object. Based on simple calculations, it is shown that an X-ray tube focal spot 0.4 × 0.8 mm in size at distances of ~1 m can be considered as a point source; however, the plane-wave approximation for such X-ray radiation with energy E = 22keV is valid for radiation source–object distances much longer than 10 m.     

X-ray phase contrast imaging with optical magnification using three-block interferometer with bi-level Fresnel zone plates

The possibility of X-ray phase contrast imaging using already suggested three-block interferometer consisting of bi-level Fresnel zone plates is considered. The interferometer operates in the amplitude-division mode and does not impose strong requirements to spatial and temporal coherences of an initial radiation. The use of the Fresnel zone plates as the interferometer blocks allows one to obtain an optically magnified image of an object and to condense the radiation incident on the tested object.     

X-ray submicrometer phase contrast imaging with a Fresnel zone plate and a two dimensional grating interferometer

The application of a two dimensional (2D) grating interferometer-Fresnel zone plate combination for quantitative submicron phase contrast imaging is reported. The combination of the two optical elements allows quick recovery of the phase shift introduced by a sample in a hard X-ray beam, avoiding artifacts observed when using the one dimensional (1D) interferometer for a sample with features oriented in the unsensitive direction of the interferometer. The setup provides submicron resolution due to the optics magnification ratio and a fine sensitivity in both transverse orientations due to the 2D analysis gratings. The method opens up possibilities for sub-micro phase contrast tomography of microscopic objects made of light and/or homogeneous materials with randomly oriented features.     

Theory of an X-ray interferometer in the form of an array of planar compound refractive lenses

The results of theoretical analysis of the interference pattern created by an X-ray multilens interferometer in the case of an arbitrary number of planar compound refractive lenses are presented. The full widths at half maximum of the resonance peaks in the transverse and longitudinal directions relative to the direction of synchrotron radiation are calculated at distances corresponding to the fractional Talbot effect. A relation between the widths is shown to exist that is very close to the width relation in the case of focusing by a single lens. A difference between the fractional and full Talbot effects is discussed, and the necessary conditions for the transverse and longitudinal coherence of radiation are analyzed, the satisfaction of which guarantees that undistorted interference peaks will be observed experimentally.     

Single-element interferometer

A very simple and stable interferometer using a single optical element - a beam-splitter cube - is presented. The device resembles a two-arm interferometer in which the arms are together in one collimated beam, and the two beam halves interfere with the help of the beam-splitter cube. The proposed device produces simultaneously two interferograms with a relative phase-shift of π (rad). Since the period of straight interference fringes can be stably controlled, the device has potential application in spatial-carrier interferometry and for flexible writing of fiber Bragg gratings.     

谱衍射干涉的计算模拟

本文提出谱衍射干涉的计算模拟方法.着重讨论了谱为几何图案时的干涉现象,得到干涉场强正比于物体沿图案路径的线积分.根据实验观察用二次位相函数来近似模拟酒精灯火焰的位相延迟,相应计算了几种特殊谱分布的衍射干涉强度分布,得到与实验相一致的结果.本文还讨论了几种特殊谱衍射干涉的特点,得到了一些结论.     

The magnesium ramsey interferometer: Applications and prospects

In this paper it will be shown that an atom interferometer, based on the coherent splitting of the atomic wavefunction by four travelling waves (Ramsey interferometer), may be explained by a purely mechanical interpretation. As our first application of this Ramsey interferometer we have measured the phase shifts respectively optical length changes in a magnesium atomic beam caused by the acceleration of the partial atomic wave in one arm of the interferometer. This acceleration was achieved by the dipole force exerted by an off-resonant crossing laser beam which interacted with the ground state part of the wavefunction only. Further applications of this interferometer and improvements due to laser cooling will be discussed.     

The phase statistics of a multichannel radar interferometer

The analysis in this paper is concerned with the problem of determining the phase statistics of the output of a multichannel coherent radar interferometer. The 2N channels of the radar consist of the outputs from N pairs of antennae. Each antenna receives a random electromagnetic wave field which has circular normal first-order statistics with an arbitrary coherence function. Each antenna in each pair receives a wave at a different time, the time difference Δt between each antenna in each pair being the same for all pairs. The signals received by each pair are independent. The signals from each pair are combined to give G(t, Δt)=Σ_k=1^N S_k(t) S_k*(t+Δt) where, for example, the signals from each antenna in the kth pair are S_k(t) and S_k(t+Δt).

The probability density function of the modulus and phase of G(t, Δt) is worked out. The joint density is shown to be a type of generalized K distribution, and the phase distribution is shown to be a hypergeometric function. The results show that it is possible to measure the phase of the coherence function of an electromagnetic wave field scattered from a randomly moving extended object (such as the ocean surface) using such a multichannel radar. This phase is related to asymmetry of the Doppler power spectrum. Furthermore, if this asymmetry is a result of surface currents on the ocean interacting with the surface waves which cause the electromagnetic scattering, then the surface currents may be measured in some sense.     

The interpretation of x-ray interferometer moiré patterns

In most experiments the x-ray-interferometer moire bands take the form of curves which complicate the problem of reconstructing the distribution pattern of deformations in single-crystal blocks giving rise to such moirés. In the paper we consider the regularities in the variation of the interplane distances and relative rotations of these planes for which moiré lines close in form to the experimental ones are obtained.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 8–12, April, 1984.