Diffraction based Hanbury Brown and Twiss interferometry performed at a hard x-ray free-electron laser

We demonstrate experimentally Hanbury Brown and Twiss (HBT) interferometry at a hard X-ray Free Electron Laser (XFEL) on a sample diffraction patterns. This is different from the traditional approach when HBT interferometry requires direct beam measurements in absence of the sample. HBT analysis was carried out on the Bragg peaks from the colloidal crystals measured at Linac Coherent Light Source (LCLS). We observed high degree (80%) spatial coherence of the full beam and the pulse duration of the monochromatized beam on the order of 11 fs that is significantly shorter than expected from the electron bunch measurements.Comment: 32 pages, 10 figures, 2 table

Statistical properties of a free-electron laser revealed by the Hanbury Brown and Twiss interferometry

We present a comprehensive experimental analysis of statistical properties of the self-amplified spontaneous emission (SASE) free-electron laser (FEL) FLASH at DESY in Hamburg by means of Hanbury Brown and Twiss (HBT) interferometry. The experiments were performed at the FEL wavelengths of 5.5 nm, 13.4 nm, and 20.8 nm. We determined the 2-nd order intensity correlation function for all wavelengths and different operation conditions of FLASH. In all experiments a high degree of spatial coherence (above 50%) was obtained. Our analysis performed in spatial and spectral domains provided us with the independent measurements of an average pulse duration of the FEL that were below 60 fs. To explain complicated behaviour of the 2-nd order intensity correlation function we developed advanced theoretical model that includes the presence of multiple beams and external positional jitter of the FEL pulses. By this analysis we determined that in most experiments several beams were present in radiating field and in one of the experiments external positional jitter was about 25% of the beam size. We envision that methods developed in our study will be used widely for analysis and diagnostics of the FEL radiation.Comment: 29 pages, 14 figures, 3 table

Spontaneous supercrystal formation during a strain-engineered metal-insulator transition

Mott metal-insulator transitions possess electronic, magnetic, and structural degrees of freedom promising next generation energy-efficient electronics. We report a previously unknown, hierarchically ordered state during a Mott transition and demonstrate correlated switching of functional electronic properties. We elucidate in-situ formation of an intrinsic supercrystal in a Ca2RuO4 thin film. Machine learning-assisted X-ray nanodiffraction together with electron microscopy reveal multi-scale periodic domain formation at and below the film transition temperature (TFilm ~ 200-250 K) and a separate anisotropic spatial structure at and above TFilm. Local resistivity measurements imply an intrinsic coupling of the supercrystal orientation to the material's anisotropic conductivity. Our findings add an additional degree of complexity to the physical understanding of Mott transitions, opening opportunities for designing materials with tunable electronic properties

3D Modelling of the Landslide Slope Stability with Seismic Effect

Abstract Three-dimensional analysis is an important and actively developing area in calculating the stability of slopes. The work was based on the results of the stability analysis of the landslide slope on the left side of the Kuban river valley above the Krasnogorsk hydropower station. The calculations were performed using the limit equilibrium methods in the three-dimensional formulation of the problem, taking into account the seismic effect. In this paper seismic effects were taken into account using the pseudostatic method. Based on the performed mathematical modelling it was shown, that direction of seismic impact changes not only the safety factor but also the spatial position of the potential landslide massif. This study proves the importance of three-dimensional calculations in the development of engineering protection measures against landslide processes.</jats:p

Landslide Processes Threatening the Historical Objects in the Nizhny Novgorod City

Abstract The article is presented in the framework of the IPL-238 project. The article is concerned with stability assessment problems of historical structures located on steep slopes of the gullies and rivers in Nizhny Novgorod City. Churches, towers, walls, and monasteries that interact with the geological environment are represented as historical natural and technical systems (HNTS). The formation and development features of slope deformations and the results of slopes’ stability calculations are described. The necessity of using modern slope stability assessment methods due to the slow but steady increase in landslide hazard for the historical and cultural heritage objects of Nizhny Novgorod, is proved. Stability calculations for the landslide-prone slopes where the Dudin and the Annunciation monasteries are located are presented.</jats:p