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Представлен метод численного решения одномерных задач магнитной гидродинамики (МГД) с учетом объемных потерь либо источников массы. Исходная система уравнений МГД записывается в квазилагранжевых переменных, определяемых по начальному распределению вещества. Построено семейство неявных полностью консервативных разностных схем. Апробация разработанной методики выполнена путем вычислительных экспериментов на задачах, для которых существуют автомодельные решения. Компьютерная 1D модель на основе квазилагранжевого подхода может быть полезна как средство экономных оценочных расчетов с частичным учетом эффектов, обусловленных двумерным или трехмерным движением вещества.

The results of the studies of the compression of the plasma of cone-cylindrical nested arrays of mixed composition at current flow through them of up to 3 MA at the Angara-5-1 facility are presented. The outer array of the nested array is a conical array of thin nylon fibers or tungsten wires, while the inner one is a cylindrical tungsten wire array. The implosion of current in this type of nested arrays is a unique opportunity for simulating the interaction of magnetized plasma flows with a strong magnetic field. In the space between the inner and outer arrays, the super-Alfven plasma flow from the outer array collides with the magnetic field of the discharge current through the inner array. As a result of this interaction in the space between arrays, different plasma flow modes are implemented: pre-Alfven (Vr VА), and a mode with the formation of the transition region—a shock wave (SW) between arrays, depending on the ratio of the plasma formation rates of arrays of nested array and on the ratio of their radii. The SW region formation in the space between arrays occurs near the inner array, where the kinetic pressure of the plasma flow from the outer array is balanced by the magnetic pressure of the discharge current of the inner array. New experimental data was obtained on the features of the SW region formation near the surface of the inner array and the nature of its change during the interaction. The use of an external conical array enabled us to obtain the SW position depending on the ratio of radii of the outer and inner arrays in one shot. It is shown that the interaction of plasma flows of the outer conical array with the magnetic field of the inner cylindrical array leads to a significant decrease in the zipper-effect at the final stage of plasma compression of the inner array and the pinch formation. The obtained experimental results are compared with the results of simulating the plasma motion between the arrays using the three-dimensional radiation-magnetohydrodynamic code MARPLE3D.

A physical and mathematical model is considered to support the investigation of the prospects of using the effect of metal’s “magnetic memory” for the nondestructive testing of items made from ferromagnetic materials located in the Earth’s magnetic field. Based on the finite-element method, an algorithm and a computer code for the 3D computations of the magnetic potential distribution in a medium with nonuniform magnetic permeability are worked out. The developed methods and software tools are used to model the leakage field near the clamped heating pipes of steam boilers. Relationships demonstrating the interdependence between the change in magnetic induction and the magnetic leakage field are obtained. Satisfactory agreement is observed between the calculated and experimental data on the distribution of the field strength of the magnetic leakage on the surface of the heating pipe.

Formation of pure gaseous water cluster in the supersonic gas flow from a conical nozzle was investigated by simulation. The simulation results show that average size of water cluster indicates a different size evolution along the gas flow, i.e., the average cluster size firstly increases to a maximum size and then decreases slowly, rather than keeps increasing like other gases. By further calculations of the nucleation rate and the growth rate of water cluster, it is found that the decrease of average size results from a high nucleation rate and a low size growth rate in the downstream of gas flow far away from conical nozzle throat. Formation of pure gaseous water cluster in the supersonic gas flow from a conical nozzle was investigated by simulation. The simulation results show that average size of water cluster indicates a different size evolution along the gas flow, i.e., the average cluster size firstly increases to a maximum size and then decreases slowly, rather than keeps increasing like other gases.

Рассмотрена физико-математическая модель, позволяющая исследовать перспективы использования эффекта «магнитной памяти металла» с целью неразрушающего контроля изделий из ферромагнитных материалов, находящихся в магнитном поле Земли. На основе метода конечных элементов разработаны алгоритм и программа для расчета в трехмерной постановке задачи о распределении магнитного потенциала в среде с неоднородной магнитной проницаемостью. Созданные методики и программные средства использованы для моделирования поля рассеяния около защемленных нагревательных труб паровых котлов. Получены соотношения, показывающие взаимосвязь между изменением магнитной индукции и магнитным полем рассеяния. Отмечено удовлетворительное совпадение расчетных и опытных данных распределения напряженности магнитного поля рассеяния на поверхности нагревательной трубы.

In this work, we optimized a clean, versatile, compact source of soft X-ray radiation $(E_{\text{x}\text{-}\text{ray}}\sim 3~\text{keV})$ with an yield per shot up to $7\times 10^{11}~\text{photons}/\text{shot}$ in a plasma generated by the interaction of high-contrast femtosecond laser pulses of relativistic intensity $(I_{\text{las}}\sim 10^{18}{-}10^{19}~\text{W}/\text{cm}^{2})$ with supersonic argon gas jets. Using high-resolution X-ray spectroscopy approaches, the dependence of main characteristics (temperature, density and ionization composition) and the emission efficiency of the X-ray source on laser pulse parameters and properties of the gas medium was studied. The optimal conditions, when the X-ray photon yield reached a maximum value, have been found when the argon plasma has an electron temperature of $T_{\text{e}}\sim 185~\text{eV}$ , an electron density of $N_{\text{e}}\sim 7\times 10^{20}~\text{cm}^{-3}$ and an average charge of $Z\sim 14$ . In such a plasma, a coefficient of conversion to soft X-ray radiation with energies $E_{\text{x}\text{-}\text{ray}}\sim 3.1\;(\pm 0.2)~\text{keV}$ reaches $8.57\times 10^{-5}$ , and no processes leading to the acceleration of electrons to MeV energies occur. It was found that the efficiency of the X-ray emission of this plasma source is mainly determined by the focusing geometry. We confirmed experimentally that the angular distribution of the X-ray radiation is isotropic, and its intensity linearly depends on the energy of the laser pulse, which was varied in the range of 50–280 mJ. We also found that the yield of X-ray photons can be notably increased by, for example, choosing the optimal laser pulse duration and the inlet pressure of the gas jet.

The adaptive mesh refinement (AMR) is a basic method for development of efficient technologies allowing a numerical solution of various problems of continuum mechanics. Numerical modeling of heat-mass transfer, hydrodynamics, structural/fracture mechanics etc. deals with non-linear strongly coupled processes which significantly differ in spatial and temporal scales. Modeling of multiscale correlated phenomena stimulates application of computational technologies using irregular grids, among which the octree meshes are the most known and widely used. Using the created data for tree-structured meshes we developed the dynamic loading balance algorithm aimed at applications to the cluster type parallel computing systems. The developed tools support functionality necessary to implement various numerical models of continuum mechanics. As an example of possible applications we discuss the constructed family of mesh projective approximations to second-order partial differential equations with a variable tensor-type coefficients. The difference operator of the scheme provides energy conservation and possesses the “self-adjoint” property which is inherent to the original differential operator, e.g. in the case of a heat transfer model. We consider numerical results obtained by solution of some model initial boundary value problems for parabolic equations using the developed AMR technique .

Methods and results of studies of the radiation spectra of high-current Z-pinches with different elemental compositions are presented. To examine a wide spectral range (Ehν = 30–3000 eV), two diagnostics tools were used—a transmission grating and a reflecting mica crystal. The radiation characteristics of the pinch are determined by its elemental composition. For currents of 2–3 MA and low-Z elements (aluminum), the hard end of the radiation spectrum is represented by spectral lines with clearly pronounced K lines, while for high-Z elements (tungsten), the spectrum lies in the softer photon energy range and is quasi-continuous. Two methods of spectrum processing were used to determine the plasma parameters. The parameters of aluminum plasma were traditionally determined from the intensity ratios of the K lines taking into account the plasma transparency for these lines. The spectra of tungsten plasma were compared with the results of computer simulations of pinch compression with allowance for both magnetohydrodynamic and plasma radiation processes. The applicability of these methods of spectral analysis is discussed.

One of the most robust methods, demonstrated up to date, of accelerating electron beams by laser-plasma sources is the utilization of plasma channels generated by the capillary discharges. These channels, i.e., plasma columns with a minimum density along the laser pulse propagation axis, may optically guide short laser pulses, thereby increasing the acceleration length, leading to a more efficient electron acceleration. Although the spatial structure of the installation is simple in principle, there may be some important effects caused by the open ends of the capillary, by the supplying channels etc., which require a detailed 3D modeling of the processes taking place in order to get a detailed understanding and improve the operation. However, the discharge plasma, being one of the most crucial components of the laser-plasma accelerator, is not simulated with the accuracy and resolution required to advance this promising technology. In the present work, such simulations are performed using the code MARPLE. First, the process of the capillary filling with a cold hydrogen before the discharge is fired, through the side supply channels is simulated. The main goal of this simulation is to get a spatial distribution of the filling gas in the region near the open ends of the capillary. A realistic geometry is used for this and the next stage simulations, including the insulators, the supplying channels as well as the electrodes. Second, the simulation of the capillary discharge is performed with the goal to obtain a time-dependent spatial distribution of the electron density near the open ends of the capillary as well as inside the capillary. Finally, to evaluate effectiveness of the beam coupling with the channeling plasma wave guide and electron acceleration, modeling of laser-plasma interaction was performed with the code INF&RNO, 11 pages, 9 figures

For several decades the capillary discharges have been under intensive investigations due to various promising applications, e.g. for the laser electron accelerators as well as for the X-ray lasers [1,2]. A major portion of the experiments were done with circular cross-section capillaries. An appropriate theoretical and numerical study of circular capillaries can be greatly simplified to a 1D model [3] assuming rotational and axial symmetries of the plasma flow in a long thin channel. On the other hand, studying capillaries with non-circular cross-section [4], which have been attracting substantially less attention, requires more complicated 2D models. Such capillaries, for example, square one, possess several advantages related to their fabrication as well as for plasma diagnostics The aim of our work is to compare the plasma density and temperature distributions formed at the quasistationary stage of the discharge. We present the results of MHD simulations of hydrogen-filled capillary discharges with circular and rectangular cross-sections under almost the same conditions characterizing the initial configurations and the external electric circuit. The simulation parameters are choosen to correspond to the capillary discharge based waveguide for the laser wakefield accelerator [5]. Bibliography [1] Leemans W. P. et al 2014 Phys. Rev. Lett. 113 245002 [2] Benware B. R. et al 1998 Phys. Rev. Lett. 81 5804 [3] Bobrova N. A. et al 2001 Phys. Rev. E 65 016407 [4] Gonsalves A. J. et al 2007 Phys. Rev. Lett. 98 025002 [5] Esarey E. et al 2009 Rev. Mod. Phys. 81 1229

X-ray spectroscopic diagnostics of laser-cluster interaction at the stage of nonadiabatic scattering of clusters and formation of a spatially uniform plasma channel has been performed. The experimental investigations have been carried out on a Ti:Sa laser setup with a pulse duration of about 65 fs and an energy up to 600 mJ. It has been shown that, within 10 ps from the beginning of a laser femtosecond pulse, the laser-cluster interaction forms a uniform plasma channel with a length of 0.4 to 1 mm with the parameters N e ∼ 1019−1020 cm−3 and T e ∼ 100 eV.

X-ray diagnostics of the interaction of femtosecond laser pulses with intensities of 1016–1018 W/cm2 with CO2 clusters and frozen nanosize water particles is carried out. The stage of cluster expansion and the formation of a plasma channel, which governs the parameters of the formed X-ray radiation source and accelerated ion flows, is studied. The measurements are based on recording spatially resolved X-ray spectra of H- and He-like oxygen ions. Utilization of Rydberg transitions for spectra diagnostics makes it possible to determine plasma parameters on a time scale of t ∼ 10 ps after the beginning of a femtosecond pulse. The role of the rear edge of the laser pulse in sustaining the plasma temperature at a level of ∼100 eV in the stage of a nonadiabatic cluster expansion is shown. The analysis of the profiles and relative intensities of spectral lines allows one to determine the temperature and density of plasma electrons and distinguish the populations of “thermal” ions and ions that are accelerated up to energies of a few tens of kiloelectronvolts. It is shown that the use of solid clusters made of frozen nanoscale water droplets as targets leads to a substantial increase in the number of fast He-like ions. In this case, however, the efficiency of acceleration of H-like ions does not increase, because the time of their ionization in plasma exceeds the time of cluster expansion.

Clustering of polar molecules (SO2) in a supersonic jet was investigated by simulation. The cluster size Nc was calculated under different gas backing pressures P0 and source temperatures T0. Based on these results, the dependence of Nc on P0 or T0 was compared with that for the gases of non-polar molecules. It is found that SO2 molecules condense very easily into clusters even when P0 is very low. This result implies that large clusters can be produced using polar molecules, which could be useful in the studies of laser-cluster interactions. Also, SO2 gas is an important component of air pollution, so the knowledge of the clustering properties of SO2 could be helpful in the study of air pollution and environment.

Bright source of soft X-ray emission was developed. Soft X-ray radiation was produced by femtosecond laser pulses irradiation of submicron size CO2 clusters. These clusters were produced in custom designed supersonic nozzle from the mixture of the 10% CO2 +90 % He expanding gases. Lithium fluorine based soft X-ray detectors was used for registration of absorption images of ultrathin (nanoscale) foils and biological structures illuminated by the developed source. It was demonstrated that even ifthe foil is essentially transparent for the soft X-ray radiation (like 100 nm thick Zr foil), the image contrast could be significantly increased due to the influence of propagation-based phase-contrast effect when detector is placed at the proper distance behind the sample (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A novel type of submicron ion radiography designed to image low-contrast objects, including nanofoils, membranes and biological structures, is proposed. It is based on femtosecond–laser-driven-cluster- plasma source of multicharged ions and polymer dosimeter film CR-39. The intense isotropic ion flow was produced by femtosecond Ti:Sa laser pulses with intensity ∼ 4x1017 W/cm2 absorbed in the supersonic jet of the mixed He and CO2 gases. Two Focusing Spectrometers with Spatial Resolution (FSSR) were used to measure X-ray spectra of H-and He-like multicharged oxygen ions. The spectra testify that ions with energy more than 300 keV were radiated in different directions from the plasma source. High contrast ion radiography images were obtained for 2000 dpi metal mesh, 1 μm polypropylene and 100 nm Zr foils as well as for the different biological objects. Images were recorded on a 1 mm thick CR-39 detector, placed in contact with back surface of the imaged samples at the distances 140 -160 mm from the ion source. The spatial resolution of the image no worse than 600 nm was provided. A difference in object thickness of 100 nm was very well resolved for both Zr and polymer foils. The ion radiography images recorded at different angles from the source, demonstrated almost uniform spatial distribution of ion with total number of 108 per shot (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

It has been shown that a femtosecond plasma of cluster targets is an almost isotropic source of fast ions and, hence, can be used to obtain ionographic images with a wide field of view. The spatial resolution of the resulting ionographic images is no worse than 600 nm, which corresponds to a uniquely high value of about 105 of the ratio of the field of view to the resolution. The use of 100–300-keV ion fluxes ensures the sensitivity of the method to the sample thickness of no worse than 100 nm even for samples consisting of light chemical elements (C, H). The proposed method can be used to obtain images of low-contrast biological objects, thin films, membranes, and other nanostructured objects.

The results of a study of a radiating Z-pinch with a profiled initial gas-density distribution over the z axis are presented. The gas distribution with the density maximum and transverse-size minimum at the discharge-gap center is formed by a pulsed gas valve with a specially designed nozzle. The parameters of X-ray radiation are measured for pinches formed in gaseous neon at currents of up to 200 kA. The experimentally selected gas density ensures the formation of a region with a typical size of less than 1 mm at the discharge-gap center. This region emits X-ray radiation in the keV photon-energy range in a time of less than 5 ns. Prospects for the development of an X-ray source based on this mechanism are discussed.

The project BELLA (LBNL, USA) is aimed to create an experimental facility for further advancing the development of laser-driven electron acceleration1. BELLA's unique attribute is the ability to use laser light to accelerate an electron beam up to 10 GeV level in a comparatively short distance of approximately one meter. The acceleration takes place during the propagation of a high power femtosecond laser pulse in the plasma formed in a capillary discharge. This capillary plasma forms a plasma channel able to guide the laser pulse, which in its turn forms a plasma wake wave that accelerates the injected electrons.

The density distribution in a pulsed xenon gas jet emanating through cylindrical and conic (supersonic) nozzles in vacuum was investigated experimentally and theoretically for different stagnation pressures and at different instants of time. The measurements were made from absorption of monochromatic soft X-rays (SXRs) (λ=13.6 nm) produced by a nanosecond laser-plasma source. Focusing normal-incidence multilayer mirrors were employed for the monochromatisation of soft X-rays and the production of transmission jet images (X-ray absorption patterns). Numerical simulations were made of the transient outflow of xenon in vacuum taking cluster production into account. The measured absolute density values and the density distribution agree nicely with the simulations.

High-resolutionK-shell spectra of a plasma created by superintense laser irradiation of micron-sized Ar clusters have been measured with an intensity above 1019W/cm2and a pulse duration of 30 fs. The total photon flux of 2 × 108photons/pulse was achieved for Heα1resonant line of Ar (λ = 3.9491 Å, 3.14 keV). In parallel with X-ray measurements, energy distributions of emitted ions have been measured. The multiply charged ions with kinetic energies up to 800 keV were observed. It is found that hot electrons produced by high contrast laser pulses allow the isochoric heating of clusters and shift the ion balance toward the higher charge states, which enhances both the X-ray line yield of the He-like argon ion and the ion kinetic energy.

The problem of increasing the mean size of clusters in gas-jet targets is tackled. Based on a mathematical model of clustering, the dependence of the cluster mean size on the nozzle length and rate of expansion is derived. The nozzle shape providing micrometer-size clusters is found. The parameters of gas-jet targets produced with this nozzle are studied in detail.

We have measured the X-ray emission spectra of a plasma generated by laser radiation with an intensity above 1019W/cm2 and a pulse duration of 30 fs acting upon an argon jet target with a large abundance of micron-sized clusters. The time variation of the X-ray yield from ions of various multiplicities, calculated within the framework of a nonstationary kinetic model, shows a good qualitative agreement with the experimental time-integrated spectrum.

Argon clusters jets were produced at the output of supersonic nozzles and used as targets for intense laser - clusters interaction experiments. They were fully characterized combining two optical diagnostics (Mach-Zehnder interferometry and Rayleigh Scattering) with the support of a numerical simulation. This study was performed with Laval and conical nozzles. Homogeneous clusters size profiles were observed at the output of the conical nozzle. Clusters mean radius was measured in the range from 200 to 300 A, increasing with the input Argon pressure varying from 20 to 60 bars.

Atomic clusters can be produced from rare gas, by spontaneous condensation during its expansion and cooling in a supersonic nozzle. When irradiated by intense laser pulses, these near-solid density clusters were observed to absorb a large fraction of the laser energy, leading to the production of highly charged ions. Based on this interaction regime, several international research groups have already demonstrated the ability to produce intense and highly repetitive X-ray and neutron sources without debris, with a relatively small experimental setup. In order to understand the different mechanisms involved in laser – cluster interaction, a complete characterization is needed for the target composed by clusters and surrounded by gas. We present a method based on two different optical diagnostics (Mach–Zehnder interferometry and Rayleigh scattering) and supported by a numerical simulation describing the gas expansion and cluster growth in the nozzle. The study was performed considering argon expanding in two types of nozzles: a Laval and a conical one. The experimental spatial profiles were observed to be in good agreement with the simulations, leading to spatial resolution of gas density, cluster size and cluster density.

A method for the asymmetric focusing of electron bunches, based on the active plasma lensing technique, is proposed. This method takes advantage of the strong inhomogeneous magnetic field generated inside the capillary discharge plasma to focus on the ultrarelativistic electrons. The plasma and magnetic field parameters inside the capillary discharge are described theoretically and modeled with dissipative magnetohydrodynamic computer simulations enabling analysis of the capillaries of rectangle cross-sections. Large aspect ratio rectangular capillaries might be used to transport electron beams with high emittance asymmetries, as well as assist in forming spatially flat electron bunches for final focusing before the interaction point.

Plasma properties inside a hydrogen-filled capillary discharge waveguide were modeled with dissipative magnetohydrodynamic simulations to enable analysis of capillaries of circular and square cross-sections implying that square capillaries can be used to guide circularly-symmetric laser beams. When the quasistationary stage of the discharge is reached, the plasma and temperature in the vicinity of the capillary axis has almost the same profile for both the circular and square capillaries. The effect of cross-section on the electron beam focusing properties were studied using the simulation-derived magnetic field map. Particle tracking simulations showed only slight effects on the electron beam symmetry in the horizontal and diagonal directions for square capillary., 6 pages, 10 figures

CO\(_2\) clusters formed in supersonic expansion of a mixed-gas of CO\(_2\)/H\(_2\) or CO\(_2\)/He through a three-staged conical nozzle have been verified by measuring the angular distribution of the light scattered from cluster target. The angular distribution is fitted by convolving a lognormal size distribution with the scattering coefficients calculated based on the Mie theory. The reliability of the size measurement is verified to be within an experimental error of 10 % using standard particles. The mean sizes of CO\(_2\) clusters at the target center for the cases of CO\(_2\)/H\(_2\) and CO\(_2\)/He gas mixtures are estimated to be 0.26 and 0.22 \(\upmu \)m, respectively. For the CO\(_2\)/H\(_2\) mixed-gas target, the variation of the mean cluster size inside the gas jet is constant within the experimental error. Furthermore, the cluster density is estimated to be \(5.5 \times 10^8\) clusters/cm\(^2\) by measuring the attenuation of the laser beam intensity. In addition, total gas density profiles in radial direction are obtained via the Abel inversion from the phase shift of the light passing through the target by utilizing an interferometer. The variation of the cluster mass fraction along the radial direction of the target is almost constant, which is consistent with a Boldarev’s model.

The article is devoted compared the results of determination of physical deterioration and condition of foundations housing facilities according to the standard procedure and the actual state of foundations, estimated by the results of a full technical inspection of construction projects

A detailed mathematical model is presented for a submicron-sized cluster formation in a binary gas mixture flowing through a three-staged conical nozzle. By measuring the angular distribution of light scattered from the clusters, the size of CO(2) clusters, produced in a supersonic expansion of the mixture gas of CO(2)(30%)/H(2)(70%) or CO(2)(10%)/He(90%), has been evaluated using the Mie scattering method. The mean sizes of CO(2) clusters are estimated to be 0.28 ± 0.03 μm for CO(2)/H(2) and 0.26 ± 0.04 μm for CO(2)/He, respectively. In addition, total gas density profiles in radial direction of the gas jet, measuring the phase shift of the light passing through the target by utilizing an interferometer, are found to be agreed with the numerical modeling within a factor of two. The dryness (= monomer/(monomer + cluster) ratio) in the targets is found to support the numerical modeling. The apparatus developed to evaluate the cluster-gas targets proved that our mathematical model of cluster formation is reliable enough for the binary gas mixture.

A study is made of the ultra-short laser pulse irradiation of Ar cluster targets. Experiments have been performed with large cluster sizes and using very high laser contrasts, which have allowed clear and unambiguous observation of exotic inner-shell transitions in near-neutral Ar ions. The interaction of the main laser pulse with the unperturbed target is a necessary requirement for observing these lines. Our measurements are supported by kinetics calculations in which a very detailed atomic model is used. The calculations predict all of the spectral features found experimentally, and support the notion that the X-ray emission arises from many ion stages of the Ar plasma, from near-neutral through He-like ions, and from a range of plasma temperatures and densities. Differences between X-ray argon clusters excited at the laser-cluster and laser-droplet interactions have been analyzed. X-ray spectral methods have been proposed to determine the parameters of the plasma formed at the early stages of its evolution. It has been shown that the spectra of hollow ions are the most informative in the first moments of the heating of a cluster, whereas the diagnostics of the late stages can be performed using the conventional lines of multicharged ions.

Differences between X-ray argon clusters excited at the laser-cluster and laser-droplet interactions have been analyzed. X-ray spectral methods have been proposed to determine the parameters of the appearing plasma at the early stages of its evolution. It has been shown that the spectra of hollow ions are the most informative in the first moments of the heating of a cluster, whereas the diagnostics of the late stages can be performed using the conventional lines of multicharged ions.

We present substantial enhancement of the accelerated ion energies up to 10–20 MeV per nucleon by utilizing the unique properties of the cluster-gas target irradiated with 40-fs laser pulses of only 150 mJ energy, corresponding to approximately tenfold increase in the ion energies compared to previous experiments using thin foil targets. A particle-in-cell simulation infers that the high energy ions are generated at the rear side of the target due to the formation of a strong dipole vortex structure in subcritical density plasmas. The demonstrated method can be important in the development of efficient laser ion accelerators for hadron therapy and other applications.

An intense isotropic source of multicharged carbon and oxygen ions with energy above 300 keV and particle number >108 per shot was obtained by femtosecond Ti:Sa laser irradiation of submicron clusters. The source was employed for high-contrast contact ionography images with 600 nm spatial resolution. A variation in object thickness of 100 nm was well resolved for both Zr and polymer foils.

The intense isotropic source of multicharged ions, with energy above 300 keV, was produced by femtosecond Ti:Sa laser pulses irradiation (intensity of ∼4×1017 W/cm2) of the He and CO2 gases mixture expanded in supersonic jet. High contrast ionography images have been obtained for 2000 dpi metal mesh, 1 μm polypropylene and 100 nm Zr foils, as well as for different biological objects. Images were recorded on 1 mm thick CR‐39 ion detector placed in contact with back surface of the imaged samples, at the distances 140–160 mm from the plasma source. The obtained spatial resolution of the image was ∼600 nm. A 100 nm object thickness difference was resolved very well for both Zr and polymer foils. The multicharged ion energy for Carbon and Oxygen ions passing through the 1 μm polypropylene foil is estimated to give the energy of more than 300 keV. An almost equal number of ions were measured with total number of about 108 per shot at a different direction from plasma source. Easy production of different sub‐MeV...

The high‐intensive source of soft X‐ray emission was developed by femtosecond laser pulses irradiation of submicron size CO2 clusters, produced in custom designed super‐sonic nozzle while mixing the 10% CO2+90% He expanding gases. The LiF crystal soft X‐ray detectors have been used for obtaining absorption images of ultrathin (nanoscale) foils and biological structures illuminated by the developed source. It was demonstrated that even if the foil is essentially transparent for the soft X‐ray radiation (like 100 nm thick Zr foil), the image contrast could be significantly increased due to the influence of propagation‐based phase‐contrast effect, by placing the detector at the proper distance from the sample.

We demonstrate generation of 10–20 MeV/u ions with a compact 4 TW laser using a gas target mixed with submicron clusters, corresponding to tenfold increase in the ion energies compared to previous experiments with solid targets. It is inferred that the high energy ions are generated due to formation of a strong dipole vortex structure. The demonstrated method has a potential to construct compact and high repetition rate ion sources for hadron therapy and other applications.

The work is devoted to some problems in numerical modelling plasma generated in the course of magnetic implosion of multiwire arrays (liners) in Z-pinch discharge mode, including numerical and theoretical analysis of quasispherical imploding conical wire arrays. Experiments were performed at ANGARA-5-1 facility (TRINITI) with the discharge current up to 3 MA. The numerical simulations were carried out on the base of 2D RMHD code MARPLE (IMM RAS). An appropriate description of the early phase of plasma generation during the electrical explosion of wires is a real challenge in MHD modeling of these experiments, in our computations we used the plasma ablation model, which allows to obtain more realistic results as compared with the models where the entire wires are considered to be initially already in plasma state. According to the experimental data we assume that the wire skeleton is stable during the overall time of the plasma generation as its density is significantly more than that of the surrounding plasma. Besides that the skeleton carries essentially less electric current than the plasma. The plasma ablation process lasts until the total wire skeleton evaporation. Experiments show that in the case of current pulse matched load the plasma generation is finished soon after the current maximum. Taking into account small diameter of the wires as compared with interwire gaps and the array dimensions plasma production is simulated by a steady source surface placed inside the computational domain. The mass ablation rate at the unit of the source surface is calculated with respect to the local distribution of the magnetic field induction. The numerical experiments showed that the plasma ablation model has a significant effect on both the entire scheme of plasma dynamics and such values as voltage drop at the load and soft X-ray yield power. The improvement of the ablation model parameters based on experimental and theoretical estimations is an issue of the day in 2D and 3D Z-pinch simulations.

MHD numerical simulations are applied for multiparameter studies of quasi-spherical magnetic compression of plasma liners created by conical multiwire arrays electrical explosion at ANGARA-5-1 facility (TRINITI) with the discharge current 2 to 3 MA and the pulse rise time about 100 ns. The description of the plasma dynamics at different stages of implosion is reproduced as a result of simulation. Numerical and experimental time profiles of voltage drop at the load and soft X-ray yield power are compared. The effect of the geometry changes upon the implosion process is studied. Numerical simulation is based on 2D RMHD code MARPLE (IMM RAS) using unstructured triangular grids. The code implements one-fluid two-temperature MHD model, grid-characteristic method for radiative energy transfer and the model of prolonged plasma ablation to simulate plasma source. The governing MHD system of is completed by electrical equation for the full circuit including the generator itself, leading-in systems and the discharge chamber with the plasma in it. Equations of state, transport and kinetic coefficients, opacity and emissivity coefficients are taken from the tables. The behavior of the discharge is satisfactorily described in general by the above RMHD model. The plasma ablation model appeared to have a significant effect on both the entire scheme of plasma dynamics and such values as voltage drop at the load and soft X-ray yield power. The improvement of this model based on experimental and theoretical estimations is an issue of the day in 2D and 3D Z-pinch simulations. The MARPLE code calibrated against the conical liners simulations proved to be a useful tool for computations aimed to optimization of the experimental setup for 3D implosion of plasma.

We used X-ray spectroscopy as a diagnostic tool for investigating the properties of laser-cluster interactions at the stage in which non-adiabatic cluster expansion takes place and a quasi-homogeneous plasma is produced. The experiment was carried out with a 10 TW, 65 fs Ti:Sa laser focused on CO2 cluster jets. The effect of different laser-pulse contrast ratios and cluster concentrations was investigated. The X-ray emission associated to the Rydberg transitions allowed us to retrieve, through the density and temperature of the emitting plasma, the time after the beginning of the interaction at which the emission occurred. The comparison of this value with the estimated time for the “homogeneous” plasma formation shows that the degree of adiabaticity depends on both the cluster concentration and the pulse contrast. Interferometric measurements support the X-ray data concerning the plasma electron density.