I.A. Schelokov

High-Frequency X-ray Beam Chopper Based on Diffraction by Surface Acoustic Waves

The diffraction of an X-ray beam on an ultrasonic wave propagating at the surface of a crystal gives rise to diffraction satellites whose temporal structure is correlated to that of the ultrasonic wave. By matching the temporal structure of the surface acoustic wave with the filling mode of the storage ring, it is possible to select or reject the incident X-ray pulses. A few examples of the performance of this MHz-range chopper for various filling modes are presented.

Diffraction of a focused X-ray beam by surface acoustic waves

Abstract This paper reports the first attempt to carry out a focusing followed by a space-time scanning of a synchrotron X-ray beam. The focusing is performed through an elliptical multilayer Bragg-Fresnel lens while the space-time scanning is due to the grazing incidence diffraction on the YZ -cut of a LiNbO 3 crystal modulated by pulsed surface acoustic waves. It opens the field of a new generation of X-ray beam control devices which should be of interest for X-ray scanning microscopy or time resolved spectroscopy. These experiments were carried out at LURE (Orsay, France).

X-ray diffraction on a multilayer mirror modulated by surface acoustic waves

Abstract This paper reports the investigation of the X-ray Bragg diffraction on a multilayer mirror modulated by a short wavelength (12 μm) surface acoustic wave. Useful parameters to determine the diffraction pattern are the amplitude, the period of the surface acoustic wave, and the deviation of the incident angle from the exact Bragg position. It is shown that changing the incident angle induces some variations in the distribution of the diffracted intensity between the diffraction orders. A model based on the dynamic diffraction theory has been developed and is compared to the experimental results.

Two-dimensional X-ray focusing by a phase Fresnel zone plate at grazing incidence

Abstract A phase Fresnel zone plate for two-dimensional X-ray focusing at grazing incidence was fabricated. A 4 × 1 μm2 X-ray source image was obtained for wavelength λ = 1.54 A .

Second generation of grazing-incidence-phase Fresnel zone plates

Second generation of grazing-incidence-phase Fresnel zone plates is presented in this paper. The term grazing-incidence discrete Fresnel lens (GIDFL) for these zone plates is proposed. This lens performs a multilevel phase modulation of the incident X-ray radiation. With the increase of the number of levels, the GIDFL virtually becomes an ideal kinoform zone plate. X-ray optical properties of a four-level GIDFL are studied here. It is found that this lens is capable of focusing X-ray radiation with an efficiency of 75%. A model is proposed which describes the diffraction properties of these lenses and allows one to calculate the focal spot intensity.

Zone plates for x-ray optics at grazing incidence angles

The results of calculations on the optical properties of zone plates at grazing incidence angles are presented. In terms of the diffraction theory, the diffraction integrals for the Fresnel zone geometries are shown to be similar at normal and grazing incidence angles in the Fresnel approximation. One-dimensional and two-dimensional cases are discussed.

Reconstruction of an object phase transmission function from in-line X-ray holograms

Abstract An approach to image formation of phase objects in partially-coherent X-ray radiation, based on stationary phase method is presented. Restrictions on applicability of the final equation are discussed. Despite that the equation is approximate, it can be used for reconstruction of object phase transmission functions. Numerical algorithm based on Tikhonov’s regularization method is described and results of their application to simulated as well as experimental data of simple objects are presented.

X-RAY DIFFRACTION BY STANDING SURFACE ACOUSTIC WAVES

Abstract X-ray diffraction by standing surface acoustic waves was investigated under total external reflection conditions. A standing surface acoustic wave was formed on the surface of a YZ-cut of a LiNbO 3 crystal by superposition of two travelling surface acoustic waves. The diffracted X-ray radiation intensity was found to oscillate with twice the frequency of the surface acoustic wave excitation.

High frequency electro-acoustic chopper for synchrotron radiation

Abstract The grazing incidence diffraction of an X-ray beam on surface acoustic waves (SAW) gives rise to diffraction satellites. A new high-frequency chopper for synchrotron radiation is presented here, based on this interaction. The temporal structure of the satellite intensities appearing in the diffracted beam can be directly correlated to the temporal structure of the acoustic waves. By electronic pulsing of the SAW emission and synchronization with the arrival of the synchrotron X-ray pulses, it is possible to select the X-ray flashes which will be diffracted in the satellites. A selection of 20% of each single X-ray pulse and an elimination of 99.7% of the unwanted ones in the hybrid mode of the ESRF (repetition frequency ∼350 kHz) has been achieved.

Two-dimensional X-ray focusing by grazing incidence phase Fresnel zone plates in Kirkpatrick-Baez scheme

Results of experimental studies using grazing incidence phase Fresnel zone plates for two-dimensional X-ray focusing in the Kirkpatrick-Baez scheme and creation of an X-ray microprobe are presented. The efficiency of incident radiation focusing by this probe is estimated. Possible applications of the such an optics scheme for X-ray diffraction investigations are considered.