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The need for precise manipulation of nanoparticles in gaseous or near-vacuum environments is encountered in many studies that include aerosol morphology, nanodroplet physics, nanoscale optomechanics, and biomolecular physics. Photophoretic forces, whereby momentum exchange between a particle and surrounding gas is induced with optical light, were recently shown to be a robust means of trapping and manipulating nanoparticles in air. We previously proposed a photophoretic "optical funnel" concept for the delivery of bioparticles to the focus of an x-ray free-electron laser (XFEL) beam for femtosecond x-ray diffractive imaging. Here, we describe the formation of a high-aspect-ratio optical funnel and provide a first experimental demonstration of this concept by transversely compressing and concentrating a high-speed beam of aerosolized viruses by a factor of three in a low-pressure environment. These results pave the way toward improved sample delivery efficiency for XFEL imaging experiments as well as other forms of imaging and spectroscopy.

The infrared transmission and reflection spectra of a series of samples of bismuth films of different thicknesses on identical single-crystal silicon substrates were measured. Transmission and reflection oscillations caused by interference on the film thickness are investigated. Properties of Si-plates are estimated. Refractive index and absorption index of bismuth are calculated. Keywords: bismuth, film, IR, interference.

The emergence of high repetition-rate X-ray free-electron lasers (XFELs) powered by superconducting accelerator technology enables the measurement of significantly more experimental data per day than was previously possible. The European XFEL will soon provide 27,000 pulses per second, more than two orders of magnitude more than any other XFEL. The increased pulse rate is a key enabling factor for single-particle X-ray diffractive imaging, which relies on averaging the weak diffraction signal from single biological particles. Taking full advantage of this new capability requires that all experimental steps, from sample preparation and delivery to the acquisition of diffraction patterns, are compatible with the increased pulse repetition rate. Here, we show that single-particle imaging can be performed using X-ray pulses at megahertz repetition rates. The obtained results pave the way towards exploiting high repetition-rate X-ray free-electron lasers for single-particle imaging at their full repetition rate.

High energy density physics 32, 63 - 69 (2019). doi:10.1016/j.hedp.2019.05.002, We present results from the SPring-8 Angstrom Compact free electron LAser (SACLA) X-ray free electron laser (XFEL) facility, using an X-ray pump, X-ray probe scheme to observe ultrafast changes in the structure of heated graphite. The 9.8 keV XFEL beam was focused to give an intensity on the order of ∼ 10$^{19}$ W/cm$^2$, and the evolution of the diffraction pattern observed up to delays of 300 fs. The interplanar diffraction peaks weaken significantly within 10s of femtoseconds, but in-plane diffraction orders i.e. those with Miller Index $(hk0)$, persist up to 300 fs, with the observed signal increasing. We interpret this as nonthermal damage through the breaking of interplanar bonds, which at longer timescales leads to ablation by removal of intact graphite sheets. Post-experiment examination of the graphite samples shows damage which is comparable in size to the range of the excited photoelectrons. These results highlight the challenges of accurately modelling X-ray driven heating, as it becomes a routine approach to generating high energy density states., Published by Elsevier, Amsterdam [u.a.]

It was demonstrated during the past decade that ultrashort intense laser pulse tightly focused deep inside a transparent dielectric generates the energy density in excess of several MJ/cm3. Such energy concentration with extremely high heating and quenching rates leads to unusual solid-plasma-solid transformation paths overcoming kinetic barriers to formation of previously unknown high-pressure material phases, which are preserved in the surrounding pristine crystal. These results were obtained with the pulse of Gaussian shape in space and in time. Recently it was shown that the Bessel-shaped pulse could transform much larger amount of a material and allegedly create even higher energy density than that was achieved with the Gaussian (GB) pulses. Here we present a succinct review of previous results and discuss the possible routes for achieving higher energy density employing the Bessel beams (BB) and take advantage of its unique properties., Comment: 6 pages

International audience; Ultrafast laser pulses create microexplosions under extreme focusing in transparent materials. The pressure created by few nano to micro joules of light is enough to generate new materials phases in the compressed zone around a laser-created void in sapphire or silicon [1,2]. Reaching extreme pressures is of fundamental interest not only for the formation of new material phases, but also for the study of the Warm Dense Matter, reproducing the state of the cores of planets with table top experiments.In this context, we have recently shown that Bessel beams create, in single shot, high aspect ratio nanovoids in the bulk of sapphire crystal. The Bessel beam possesses a central intense core surrounded by several lobes of lower intensity. The focal line can be arbitrarily long while having a constant focus diameter. In our case, the focal diameter is 0.66 µm FWHM, extending over ~30 µm. The voids were generated by short, 140 fs, and long, 3 ps, laser pulses at 2 µJ, 800 nm. [3]The analysis of the post-mortem samples shows that the pressures reached are in the range of tens of Megabars on a volume that is 2 orders of magnitude higher than what was reached with extremely focused Gaussian beams. Yet the light-matter interaction entangles propagation and permittivity change due to the swift conversion of the initial transparent medium into a dense plasma state, the Bessel beam is a quasi-2D system where Kerr nonlinearity is almost negligible for high cone angle focusing as in our case. We report on a new interaction mode provided by the Bessel beam focusing: numerical simulations, both from dynamical nonlinear Schrödinger equation for pulse propagation and static Maxwell models provide insights in the interplay between the incident laser field and the gradient of permittivity. Significant field-enhancement is observed which explains the extreme absorption and therefore extreme thermodynamic conditions reported experimentally.The new interaction provided by the Bessel beam is a novel approach to reach extreme conditions on macroscopic volumes. We believe this will open novel routes for applications and fundamental physics based on laser-matter interaction.

Journal of synchrotron radiation 24(6), 1296 - 1298 (2017). doi:10.1107/S1600577517011961, The success of diffraction experiments from weakly scattering samples strongly depends on achieving an optimal signal-to-noise ratio. This is particularly important in single-particle imaging experiments where diffraction signals are typically very weak and the experiments are often accompanied by significant background scattering. A simple way to tremendously reduce backgroundscattering by placing an aperture downstream of the sample has been developed and its application in a single-particle X-ray imaging experiment at FLASH is demonstrated. Using the concept of a post-sample aperture it was possible to reduce the background scattering levels by two orders of magnitude., Published by IUCr, Chester

It has been proven that the intense tightly focused Gauss beam (GB) generates pressures in excess of a few TPa creating the novel super-dense phases of Aluminium and silicon [1-5]. Recently it was demonstrated that the Bessel beam (BB) focused inside sapphire produced the cylindrical void being two orders of magnitude larger than that generated by the GB [6-8]. Analysis of the experimental data presented below allows making the remarkable conclusions based solely on the void size measurements without any ad hoc assumptions about the interaction process. First, the void size is direct evidence of strong (>40%) absorption of the pulse energy. Second, it is a direct experimental evidence of the high-energy concentration in the central spike of the focus. The unique features of the intense Bessel beam interaction then allow understanding the experimental observation. This interaction generates early in the pulse time the spatial distribution of excited permittivity changing from positive to negative values. Then the light interacts with zero-real-permittivity surface, separating plasma and dielectric areas, which leads to high energy concentration near the axis of cylindrical focus up to several MJ/cm3 (pressure range of 4-8 TPa). The effect depends on the angle between the permittivity gradient and the field polarisation. High pressure generates intense cylindrical shock/ rarefaction waves, which led to formation of void and compressed shell. We demonstrate that the Bessel beam proves to be an effective tool for producing extreme pressure/temperature conditions on the laboratory tabletop. It appears that adjusting polarisation and permittivity gradient might be a novel way for increasing the maximum pressure. This tool allows for search of novel high-pressure material phases, for the 3D laser machining and for creating Warm Dense Matter as those in star cores., Draft-01, 18 pages, 4 figures, presented at International Conference on Laser Ablation COLA-2017 in Marseille, 4-8 September 2017. The latest version has updated text and figures

Delivering sub-micrometer particles to an intense x-ray focus is a crucial aspect of single-particle diffractive-imaging experiments at x-ray free-electron lasers. Enabling direct visualization of sub-micrometer aerosol particle streams without interfering with the operation of the particle injector can greatly improve the overall efficiency of single-particle imaging experiments by reducing the amount of time and sample consumed during measurements. We have developed in-situ non-destructive imaging diagnostics to aid real-time particle injector optimization and x-ray/particle-beam alignment, based on laser illumination schemes and fast imaging detectors. Our diagnostics are constructed to provide a non-invasive rapid feedback on injector performance during measurements, and have been demonstrated during diffraction measurements at the FLASH free-electron laser., 15 pages

International audience; We show that micro‐explosions generated by tightly focused single pulses of a femtosecond laser in olivine have produced change of iron valence state. Chemical and structural changes were investigated using synchrotron X‐ray spectroscopy, and Raman scattering. Near edge X‐ray absorption fine structure (NEXAFS) spectra from laser‐affected zone of olivine crystal indicate a modified chemical bonding and a possible formation of regions containing a new crystalline phases of iron. Raman scattering from the laser‐affected zone regions reveals loss of crystalline order and formation of a mixture of nano‐crystallites due to melting and re‐solidification of olivine. These results indicate that spatial separation between ions of different mass occurs in hot, highly excited olivine. The present study confirms that this mechanism may present a general pathway toward creation of novel crystalline and amorphous nano‐materials using fs laser‐induced confined micro‐explosions.

We have developed a high-aspect ratio optical pipeline aiming to produce a highly collimated stream of micron-size particles in either gaseous or vacuum environments. A hollow, first-order quasi-Bessel beam with variable divergence was generated with a phase-only spatial light modulator (SLM), by superimposing the quadratic phase of a lens and an axicon with a 0.5° base angle. The beam was further re-imaged to form a centimetre-long funnel beam with ~5μm diameter and up to 2000 length-to-diameter aspect ratio. The divergence of the central core of the Bessel beam was controlled by varying the effective lens in the hologram. The SLM-based optical beam was compared to a similar beam composed using a physical axicon. The experimental tests were conducted with 2-μm size polystyrene spherical particles to evaluate the optical force. We present estimated optical forces exerted on the particles in the transverse plane, both depending on the particle size, laser power, and background-gas pressure. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Представлены материалы по обоснованию и необходимости автоматизации расчета режимов дуговой сварки под слоем флюса. Разработан программный комплекс по расчету параметров режима дуговой сварки под слоем флюса для низкоуглеродистых сталей. Для расчета режима сварки установлены зависимости влияния погонной энергии сварки на скорость охлаждения металла шва. Materials on substantiation and necessity of automation of calculation of the arc welding modes under a layer of flux are presented. The software complex for calculating the parameters of the arc welding mode under a layer of flux for low-carbon steels is developed. Dependences of welding heat effect on the cooling rate of the weld seam metal in order to calculate the welding mode are established. Уланов Алексей Михайлович, аспирант кафедры оборудования и технологии сварочного производства, Южно-Уральский государственный университет. Ulanov Alexey Mikhailovich, post-graduate student of the Welding Equipment and Technology department, South Ural State University. Иванов Михаил Александрович, кандидат технических наук, доцент кафедры оборудования и технологии сварочного производства, Южно-Уральский государственный университет. Тел.: (351)2679221. E-mail: IvanovM@yandex.ru Ivanov Mikhail Alexandrovich, candidate of engineering science, associate professor of the Welding Equipment and Technology department, South Ural State University. Tel.: (351)2679221. E-mail: IvanovM@yandex.ru. Роде Владимир Владимирович, студент кафедры оборудования и технологии сварочного производства, Южно-Уральский государственный университет. Тел.: (351)2679221. Rode Vladimir Vladimirovich, student of the Welding Equipment and Technology department, South Ural State University. Tel.: (351)2679221. Данилкин Павел Алексеевич, студент кафедры оборудования и технологии сварочного производства, Южно-Уральский государственный университет. Тел.: (351)2679221. Danilkin Pavel Alexeevich, student of the Welding Equipment and Technology department, South Ural State University.

This letter is the first demonstration of material modification using tightly focused femtosecond laser vortex beams. Double-charge femtosecond vortices were synthesized with the polarization-singularity beam converter described in Ref [1] and then focused using moderate and high numerical aperture optics (viz., NA = 0.45 and 0.9) to ablate fused silica and soda-lime glasses. By controlling the pulse energy we consistently machine high-quality micron-size ring-shaped structures with less than 100 nm uniform groove thickness., 8 pages, 3 figures, 10 references; submitted to Appl. Phys. Lett. on May 31, 2010

This letter is the first demonstration of material modification using tightly focused femtosecond laser vortex beams. Double-charge femtosecond vortices were synthesized with the polarization-singularity beam converter described in Ref [1] and then focused using moderate and high numerical aperture optics (viz., NA = 0.45 and 0.9) to ablate fused silica and soda-lime glasses. By controlling the pulse energy we consistently machine high-quality micron-size ring-shaped structures with less than 100 nm uniform groove thickness., Comment: 8 pages, 3 figures, 10 references; submitted to Apl. Phys. Lett. 31 May 2010

Transient state of femtosecond laser excited bismuth has been studied by various groups with time-resolved optical, x-ray, and electron probes at the deposited energy density from below through up to several times the equilibrium enthalpy of melting. However, the interpretations of the experimental results are controversial: the optical probes reveal the absence of transition to the melting phase while the authors of x-ray and electron diffraction experiments claim the observation of ultrafast non-thermal melting. The presented analysis, based on temperature dependence of bismuth optical properties, unequivocally shows a purely thermal nature of all the observed fs-laser induced transformations in bismuth., Comment: 20 pages, 6 figures, to be presented at the Conference on Laser Ablation COLA'2009, Singapore, 21-26 November 2009

International audience

We report the production of a hierarchically nanostructured magnetic carbon foam by high-repetition-rate laser ablation of glassy carbon in Ar. The clusters contain both sp2 and sp3 bonded carbon atoms. The material contains graphite-like sheets with hyperbolic curvature, as proposed for "schwarzite". In addition to other unusual properties, the all-carbon nanofoam exhibits para- and maybe ferromagnetic behavior up to 90 K, with a narrow hysteresis curve, susceptibility of the order of 10-5 emu/g Oe, and a high saturation magnetization (up to 0.8 emu/g at 1.8 K). We postulate that localized unpaired spins occur because of topological and bonding defects associated with the sheet curvature, and that these spins are stabilized for >1 year due to the steric protection offered by the convoluted sheets. © 2004 Elsevier B.V. All rights reserved. 290-291 PART 1 298 301 298-301

We report production of nanostructured carbon foam by a high-repetition-rate, high-power laser ablation of glassy carbon in Ar atmosphere. A combination of characterization techniques revealed that the system contains both sp2 and sp3 bonded carbon atoms. The material is a novel form of carbon in which graphite-like sheets fill space at very low density due to strong hyperbolic curvature, as proposed for ?schwarzite?. The foam exhibits ferromagnetic-like behaviour up to 90 K, with a narrow hysteresis curve and a high saturation magnetization. Such magnetic properties are very unusual for a carbon allotrope. Detailed analysis excludes impurities as the origin of the magnetic signal. We postulate that localized unpaired spins occur because of topological and bonding defects associated with the sheet curvature, and that these spins are stabilized due to the steric protection offered by the convoluted sheets., Comment: 14 pages, including 2 tables and 7 figs. Submitted to Phys Rev B 10 September 2003

Structural dynamics 2(4), 041717(2015). doi:10.1063/1.4922648, A major challenge in high-resolution x-ray free-electron laser-based coherent diffractive imaging is the development of aerosol injectors that can efficiently deliver particles to the peak intensity of the focused X-ray beam. Here, we consider the use of a simple convergent-orifice nozzle for producing tightly focused beams of particles. Through optical imaging we show that 0.5 μm particles can be focused to a full-width at half maximum diameter of 4.2 μm, and we demonstrate the use of such a nozzle for injecting viruses into a micro-focused soft-X-ray FEL beam., Published by AIP Publishing LLC, Melville, NY

Journal of applied crystallography 51(1), 133 - 139 (2018). doi:10.1107/S1600576717018131, High-resolution Bragg diffraction from aerosolized single granulovirus nano-crystals using an X-ray free-electron laser is demonstrated. The outerdimensions of the in-vacuum aerosol injector components are identical toconventional liquid-microjet nozzles used in serial diffraction experiments,which allows the injector to be utilized with standard mountings. As comparedwith liquid-jet injection, the X-ray scattering background is reduced by severalorders of magnitude by the use of helium carrier gas rather than liquid. Suchreduction is required for diffraction measurements of small macromolecularnanocrystals and single particles. High particle speeds are achieved, making theapproach suitable for use at upcoming high-repetition-rate facilities., Published by Munksgaard, Copenhagen

IUCrJ 5(5), 574 - 584 (2018). doi:10.1107/S2052252518008369, Liquid microjets are a common means of delivering protein crystals to the focus of X-ray free-electron lasers (FELs) for serial femtosecond crystallography measurements. The high X-ray intensity in the focus initiates an explosion of the microjet and sample. With the advent of X-ray FELs with megahertz rates, the typical velocities of these jets must be increased significantly in order to replenish the damaged material in time for the subsequent measurement with the next X-ray pulse. This work reports the results of a megahertz serial diffraction experiment at the FLASH FEL facility using 4.3 nm radiation. The operation of gas-dynamic nozzles that produce liquid microjets with velocities greater than 80 m s$^{−1}$ was demonstrated. Furthermore, this article provides optical images of X-ray-induced explosions together with Bragg diffraction from protein microcrystals exposed to trains of X-ray pulses repeating at rates of up to 4.5 MHz. The results indicate the feasibility for megahertz serial crystallography measurements with hard X-rays and give guidance for the design of such experiments., Published by Chester

Optics express 24(6), 6507–6521(2016). doi:10.1364/OE.24.006507, Delivering sub-micrometer particles to an intense x-ray focus is a crucial aspect of single-particle diffractive-imaging experiments at x-ray free-electron lasers. Enabling direct visualization of sub-micrometer aerosol particle streams without interfering with the operation of the particle injector can greatly improve the overall efficiency of single-particle imaging experiments by reducing the amount of time and sample consumed during measurements. We have developed in-situ non-destructive imaging diagnostics to aid real-time particle injector optimization and x-ray/particle-beam alignment, based on laser illumination schemes and fast imaging detectors. Our diagnostics are constructed to provide a non-invasive rapid feedback on injector performance during measurements, and have been demonstrated during diffraction measurements at the FLASH free-electron laser., Published by Washington, DC

Tecnologies de transferència de calor de nova generació, amb menys consum d'energia per al benestar de la societat són necessàries. En aquest sentit, els líquids iònics (ILS) són en l'actualitat els fluids més investigats per la seva major estabilitat tèrmica i la naturalesa no volàtil que els fan més avantatjosos que els fluids convencionals. A més, la dispersió de nanopartícules metàl·liques en els fluids convencionals també estan sent investigats en els últims temps a causa de la seva major conductivitat tèrmica, millora en la fluïdesa reduint el cost de bombament, i absència de sedimentació de sal. Aquestes característiques fan fascinants als nanofluidos (NFs) com una bona alternativa a les solucions salines convencionals per a aplicacions de transferència de calor. En aquest treball, ILS basats en el catió imidazoli es van preparar amb anions com ara clorur, bromur, iodur i tetrafluroborate. Diverses propietats termofísiques com la conductivitat tèrmica, capacitat calorífica, densitat i viscositat d'aquests fluids van ser investigades en detall. Com que només hi ha molt pocs treballs publicats sobre NPs de metalls de transició en líquids iònics per a aplicacions de transferència de calor, aquesta tesi s'enfoca en el disseny de les ILS desitjats i en el desenvolupament de materials compostos de metalls de transició NPs amb els ILS iònics preparats. Per a aquest propòsit, es van utilitzar NPs de ruteni (Ru) i plata (Ag). Les propietats tèrmiques d'aquests líquids iònics es van millorar mitjançant la preparació in situ de compostos d'ILS amb nanopartícules de ruteni sense utilitzar agents tensioactius, a temperatura ambient. Per a la preparació dels ionanofluidos (INFs) amb plata, es van utilitzar nanoparículas amb morfologies variables, de 1D, 2D i 3D. Aquests ionanofluids redueixen la viscositat de líquids iònics de base juntament amb la millora en la seva conductivitat tèrmica. Des d'aquesta perspectiva, un catalitzador de carbó amb 5% de ruteni amb àcid de Bronsted IL [Hmim] [HSO4] com un co-catalitzador va ser desenvolupat per hidrogenólisis selectiva del bio-derivat d'àcid levulínic (LA) gamma-valerolactona (GVL) , el qual és un additiu de combustibles., Tecnologías de transferencia de calor de nueva generación, con menos consumo de energía para el bienestar de la sociedad son necesarias. En este sentido, los líquidos iónicos (ILs) son en la actualidad los fluidos más investigados debido a su mayor estabilidad térmica y la naturaleza no volátil que los hacen más ventajosos que los fluidos convencionales. Además, la dispersión de nanopartículas metálicas en los fluidos convencionales también están siendo investigados en los últimos tiempos debido a su mayor conductividad térmica, mejora en la fluidez reduciendo el coste de bombeo, y ausencia de sedimentación de sal. Estas características hacen fascinantes a los nanofluidos (NFs) como una buena alternativa a las soluciones salinas convencionales para aplicaciones de transferencia de calor. En este trabajo, ILs basados en el catión imidazolio se prepararon con aniones tales como cloruro, bromuro, yoduro y tetrafluroborate. Varias propiedades termofísicas como la conductividad térmica, capacidad calorífica, densidad y viscosidad de estos fluidos fueron investigadas en detalle. Como sólo hay muy pocos trabajos publicados sobre NPs de metales de transición en líquidos iónicos para aplicaciones de transferencia de calor, esta tesis se enfoca en el diseño de las ILs deseados y en el desarrollo de materiales compuestos de metales de transición NPs con los ILs iónicos preparados. Para este propósito, se utilizaron NPs de rutenio (Ru) y plata (Ag). Las propiedades térmicas de estos líquidos iónicos se mejoraron mediante la preparación in situ de compuestos de ILs con nanopartículas de rutenio sin utilizar agentes tensioactivos, a temperatura ambiente. Para la preparación de los ionanofluidos (INFs) con plata, se utilizaron nanoparículas con morfologías variables, de 1D, 2D y 3D. Estos ionanofluids reducen la viscosidad de líquidos iónicos de base junto con la mejora en su conductividad térmica. Desde esta perspectiva, un catalizador de carbon con 5% de rutenio con ácido de Bronsted IL [Hmim] [HSO4] como un co-catalizador fue desarrollado para hidrogenólisis selectiva del bio-derivado de ácido levulínico (LA) gamma-valerolactona (GVL), el cual es un aditivo de combustibles., New generation heat transfer technologies with less energy consumption and improved economy are needed for welfare of the society. In this regard, ionic liquids (ILs) are most investigated fluids due to their higher thermal stability and non-volatile nature which make them more advantageous than the conventional fluids. In addition, dispersion of metal nanoparticles in conventional fluids are also being investigated in recent times due to their higher thermal conductivity, easy flow, which reduce pumping cost as well as no salt sedimentation. These fascinating features make NFs as a good alternative to the conventional salt solutions for heat transfer applications. In this work, imidazolium cation based ILs were prepared with variation in anions such as chloride, bromide, iodide and tetrafluroborate. Several thermophysical properties as thermal conductivity, heat capacity, density and viscosity of these fluids were investigated in detail. As there are only a very few reports available on transition metal NPs in ILs for heat transfer applications, this thesis work is focused on first designing the desired ILs and then developing composites of transition metal NPs with the prepared ionic ILs. For this purpose, NPs of ruthenium (Ru) and silver (Ag) were used. Thermal properties of these ILs were improved by in-situ preparation of composites of ILs with ruthenium nanoparticles without using capping agents or surfactants at room temperature. For preparing Ag containing ionanofluids (INFs), readily available NPs of Ag with variable morphologies, of 1D, 2 D and 3 D were used. These ionanofluids reduced the viscosity of base ILs along with the enhancement in their thermal conductivity. From this perspective, Carbon supported 5% ruthenium catalyst with Bronsted acidic IL [Hmim][HSO4] as a co-catalyst was developed for selective hydrogenolysis of bio-derived levulinic acid (LA) gamma-valerolactone (GVL) which is fuel additive.