Alexander Goikhman

Fourier crystal diffractometry based on refractive optics

X-ray refractive lenses are proposed as a Fourier transformer for high-resolution X-ray crystal diffraction. By employing refractive lenses the wave transmitted through the object converts into a spatial intensity distribution at its back focal plane according to the Fourier-transform relations. A theoretical consideration of the Fourier-transform technique is presented. Two types of samples were studied in Bragg reflection geometry: a grating made of strips of a thin SiO2 film on an Si substrate and a grating made by profiling an Si crystal. Fourier patterns recorded at different angles along the rocking curves of the Si 111 Bragg reflection were analysed.

Magnetic Properties of Heusler-Type Microwires and Thin Films

In this paper, we studied magnetic properties of Heusler-type glass-covered microwires and thin films. The results have shown that we succeeded to prepare Ni-Mn-In thin films and Ni-Mn-Ga and Ni-Mn-In microwires that have martensitic and austenitic phases at room temperature.

Ni-Mn-In Heusler Alloy Thin Films Grown by Pulsed Laser Deposition

We report on the results of the magnetic and structure properties investigation of Heusler alloy films. Ni-Mn-In thin films were formed by pulsed laser deposition. Stoichiometry was varied and controlled by co-deposition technique. The different deposition conditions and influence of the annealing temperature on the film composition were investigated using Auger electron spectroscopy and Rutherford backscattering spectrometry. The optimal annealing temperature was found to be 620 K. The set of the films deposited on the oxidized Si (100) substrate at room temperature and annealed at 620 K was investigated using X-ray diffractometry at room temperature and Vibrating sample magnetometery at low temperatures. The crystal structure was found to be a mixture of austenitic and martensitic phases at room temperature. Decreasing of Curie temperature from 270 K to 250 K with the decreasing of In concentration from 20 at % to 15 at % was observed.

Highly porous nanoberyllium for X-ray beam speckle suppression

A speckle suppression device containing highly porous nanoberyllium is proposed for manipulating the spatial coherence length and removing undesirable speckle structure during imaging experiments.

Protective radiolucent aluminium oxide coatings for beryllium X-ray optics

Beryllium, being one of the most transparent materials to X-ray radiation, has become the material of choice for X-ray optics instrumentation at synchrotron radiation sources and free-electron laser facilities. However, there are concerns due to its high toxicity and, consequently, there is a need for special safety regulations. The authors propose to apply protective coatings in order to seal off beryllium from the ambient atmosphere, thus preventing degradation processes providing additional protection for users and prolonging the service time of the optical elements. This paper presents durability test results for Be windows coated with atomic-layer-deposition alumina layers run at the European Synchrotron Radiation Facility. Expositions were performed under monochromatic, pink and white beams, establishing conditions that the samples could tolerate without radiation damage. X-ray treatment was implemented in various environments, i.e. vacuum, helium, nitrogen, argon and dry air at different pressures. Post-process analysis revealed their efficiency for monochromatic and pink beams.

Pulse-resolved intensity measurements at a hard X-ray FEL using semi-transparent diamond detectors

Solid-state ionization chambers are presented based on thin diamond crystals that allow pulse-resolved intensity measurements at a hard X-ray free-electron laser (FEL), up to the 4.5 MHz repetition rate that will become available at the European XFEL. Due to the small X-ray absorption of diamond the thin detectors are semi-transparent which eases their use as non-invasive monitoring devices in the beam. FELs are characterized by strong pulse-to-pulse intensity fluctuations due to the self-amplified spontaneous emission (SASE) process and in many experiments it is mandatory to monitor the intensity of each individual pulse. Two diamond detectors with different electrode materials, beryllium and graphite, were tested as intensity monitors at the XCS endstation of the Linac Coherent Light Source (LCLS) using the pink SASE beam at 9 keV. The performance is compared with LCLS standard monitors that detect X-rays backscattered from thin SiN foils placed in the beam. The graphite detector can also be used as a beam position monitor although with rather coarse resolution.

X-ray refractive optics as a Fourier transformer for high resolution diffraction

Refractive optics is proposed as a Fourier transformer for high resolution X-ray crystal diffraction. Employing refractive lenses the wave transmitted through the object transforms into spatial intensity distribution at its back focal plane according to the Fourier relations. A theoretical consideration of the Fourier transform technique is presented. Two types of samples were studied in Bragg reflection geometry: a grating made of strips of a thin SiO2 film on Si substrate and a grating made by profiling a Si crystal. Rocking curves of Si(111) Bragg reflection and corresponding Fourier patterns were analyzed.