In addition to their visible motion such as swimming(e.g.,with the help offlagella),bacteria can also exhibit nanomotion that is detectable only with highly sensitive instruments,and this study shows that it is possibl...In addition to their visible motion such as swimming(e.g.,with the help offlagella),bacteria can also exhibit nanomotion that is detectable only with highly sensitive instruments,and this study shows that it is possible to detect bacterial nanomotion using an AFM detection system.The results show that the nanomotion characteristics depend on the bacterial strain,and that nanomotion can be used to sense the metabolic activity of bacteria because the oscillations are sensitive to the food preferences of the bacteria and the type of surrounding medium.展开更多
Coherent motion of particles in a plasma can imprint itself on radiation.The recent advent of high-power lasers—allowing the nonlinear inverse Compton-scattering regime to be reached—has opened the possibility of lo...Coherent motion of particles in a plasma can imprint itself on radiation.The recent advent of high-power lasers—allowing the nonlinear inverse Compton-scattering regime to be reached—has opened the possibility of looking at collective effects in laser–plasma interactions.Under certain conditions,the collective interaction of many electrons with a laser pulse can generate coherent radiation in the hard x-ray regime.This perspective paper explains the limitations under which such a regime might be attained.展开更多
Directed x-rays produced in the interaction of sub-picosecond laser pulses of moderate relativistic intensity with plasma of near-critical density are investigated. Synchrotron-like (betatron) radiation occurs in the ...Directed x-rays produced in the interaction of sub-picosecond laser pulses of moderate relativistic intensity with plasma of near-critical density are investigated. Synchrotron-like (betatron) radiation occurs in the process of direct laser acceleration (DLA) of electrons in a relativisticlaser channel when the electrons undergo transverse betatron oscillations in self-generated quasi-static electric and magnetic fields. In anexperiment at the PHELIX laser system, high-current directed beams of DLA electrons with a mean energy ten times higher than the ponderomotive potential and maximum energy up to 100 MeV were measured at 10^(19) W/cm^(2)laser intensity. The spectrum of directed x-raysin the range of 5–60 keV was evaluated using two sets of Ross filters placed at 0°and 10°to the laser pulse propagation axis. The differential x-ray absorption method allowed for absolute measurements of the angular-dependent photon fluence. We report 10^(13) photons/sr withenergies >5 keV measured at 0°to the laser axis and a brilliance of 10^(21) photons s^(−1) mm^(−2) mrad−2(0.1%BW)−1. The angular distributionof the emission has an FWHM of 14°–16°. Thanks to the ultra-high photon fluence, point-like radiation source, and ultra-short emissiontime, DLA-based keV backlighters are promising for various applications in high-energy-density research with kilojoule petawatt-class laserfacilities.展开更多
Joint experiments(JEs)on small tokamaks have been regularly performed between 2005 and 2015 under the framework of the International Atomic Energy Agency(IAEA)coordinated research projects(CRPs).This paper describes t...Joint experiments(JEs)on small tokamaks have been regularly performed between 2005 and 2015 under the framework of the International Atomic Energy Agency(IAEA)coordinated research projects(CRPs).This paper describes the background and the rationale for these experiments,how they were organized and executed,main areas of research covered during these experiments,main results,contributions to mainstream fusion research,and discusses lessons learned and outcomes from these activities.We underline several of the most important scientific outputs and also specific outputs in the education of young scientists and scientists from developing countries and their importance.展开更多
Irradiation of a thin metallic wire with an intense femtosecond laser pulse creates a strong discharge wave that travels as a narrow pulse along the wire surface.This traveling discharge efficiently emits secondary ra...Irradiation of a thin metallic wire with an intense femtosecond laser pulse creates a strong discharge wave that travels as a narrow pulse along the wire surface.This traveling discharge efficiently emits secondary radiation with spectral characteristics that are mostly defined by the wire geometry.Several examples of designs are considered here in the context of generation of intense terahertz radiation with controllable characteristics for various scientific and technological applications.The proposed setup may be easily realized,and it has the merits of robustness,versatility,and high conversion efficiency(reaching several percent)of laser energy to terahertz radiation.展开更多
A neural network-based approach is proposed both for reconstructing the focal spot intensity profile and for estimating the peak intensity of a high-power tightly focused laser pulse using the angular energy distribut...A neural network-based approach is proposed both for reconstructing the focal spot intensity profile and for estimating the peak intensity of a high-power tightly focused laser pulse using the angular energy distributions of protons accelerated by the pulse from rarefied gases.For these purposes,we use a convolutional neural network architecture.Training and testing datasets are calculated using the test particle method,with the laser description in the form of Stratton-Chu integrals,which model laser pulses focused by an off-axis parabolic mirror down to the diffraction limit.To demonstrate the power and robustness of this method,we discuss the reconstruction of axially symmetric intensity profiles for laser pulses with intensities and focal diameters in the ranges of 10^(21)-10^(23) W cm^(−2) and ~(1-4)λ,respectively.This approach has prospects for implementation at higher intensities and with asymmetric laser beams,and it can provide a valuable diagnostic method for emerging extremely intense laser facilities.展开更多
In an experiment carried out at the Prague Asterix Laser System at laser intensities relevant to shock ignition conditions(I>10^(16) W/cm^(2)),the heating and transport of hot electrons were studied by using severa...In an experiment carried out at the Prague Asterix Laser System at laser intensities relevant to shock ignition conditions(I>10^(16) W/cm^(2)),the heating and transport of hot electrons were studied by using several complementary diagnostics,i.e.,K_(α)time-resolved imaging,hard x-ray filtering(a bremsstrahlung cannon),and electron spectroscopy.Ablators with differing composition from low Z(parylene N)to high Z(nickel)were used in multilayer planar targets to produce plasmas with different coronal temperature and collisionality and modify the conditions of hot-electron generation.The variety of available diagnostics allowed full characterization of the population of hot electrons,retrieving their conversion efficiency,time generation and duration,temperature,and angular divergence.The obtained results are shown to be consistent with those from detailed simulations and similar inertial confinement fusion experiments.Based on the measured data,the advantages,reliability,and complementarity of the experimental diagnostics are discussed.展开更多
Based on the standard definition of the product (concatenation), the natural non-negative degree of the language is introduced. Root extraction is the reverse operation to it, and it can be defined in several differen...Based on the standard definition of the product (concatenation), the natural non-negative degree of the language is introduced. Root extraction is the reverse operation to it, and it can be defined in several different ways. Despite the simplicity of the formulation of the problem of extracting the root, the authors could not find any description of it in the literature (as well as on the Internet), including even its formulation. Most of the material in this article is devoted to the simplest version of the formulation: the root of the 2<sup>nd</sup> degree for the 1-letter alphabet, but many of the provisions of the article are generalized to more complex cases. Apparently, for a possible future description of a polynomial algorithm for solving at least one of the described statements of root extraction problems, it is first necessary to really analyze in detail such a special case, that is: either describe the necessary polynomial algorithm, or, conversely, show that the problem belongs to the class of NP-complete problems. Thus, in this article, we do not propose a polynomial algorithm for the problems under consideration;however, the models described here should help in constructing appropriate heuristic algorithms for their solution. A detailed description of the possible further application of such heuristic algorithms is beyond the scope of this article. .展开更多
We review the development of High Energy Density Physics(HEDP)with intense heavy ion beams as a tool to induce extreme states of matter.The development of this field connects intimately to the advances in accelerator ...We review the development of High Energy Density Physics(HEDP)with intense heavy ion beams as a tool to induce extreme states of matter.The development of this field connects intimately to the advances in accelerator physics and technology.We will cover the generation of intense heavy ion beams starting from the ion source and follow the acceleration process and transport to the target.Intensity limitations and potential solutions to overcome these limitations are discussed.This is exemplified by citing examples from existing machines at the Gesellschaft fur Schwerionenforschung(GSI-Darmstadt),the Institute of Theoretical and Experimental Physics in Moscow(ITEP-Moscow),and the Institute of Modern Physics(IMP-Lanzhou).Facilities under construction like the FAIR facility in Darmstadt and the High Intensity Accelerator Facility(HIAF),proposed for China will be included.Developments elsewhere are covered where it seems appropriate along with a report of recent results and achievements.展开更多
Polycrystalline diamond(PCD) films 100 mm in diameter are grown by 915 MHz microwave plasma chemical vapor deposition(MPCVD) at different process parameters,and their thermal conductivity(TC) is evaluated by a laser f...Polycrystalline diamond(PCD) films 100 mm in diameter are grown by 915 MHz microwave plasma chemical vapor deposition(MPCVD) at different process parameters,and their thermal conductivity(TC) is evaluated by a laser flash technique(LFT) in the temperature range of230-380 K.The phase purity and quality of the films are assessed by micro-Raman spectroscopy based on the diamond Raman peak width and the amorphous carbon(a-C) presence in the spectra.Decreasing and increasing dependencies for TC with temperature are found for high and low quality samples,respectively.TC,as high as 1950 ± 230 W m^(-1) K^(-1) at room temperature,is measured for the most perfect material.A linear correlation between the TC at room temperature and the fraction of the diamond component in the Raman spectrum for the films is established.展开更多
We investigate the structural and electrical properties of carbon-ion-implanted ultrananocrystalline diamond(UNCD)films. Impedance spectroscopy measurements show that the impedance of diamond grains is relatively stab...We investigate the structural and electrical properties of carbon-ion-implanted ultrananocrystalline diamond(UNCD)films. Impedance spectroscopy measurements show that the impedance of diamond grains is relatively stable, while that of grain boundaries(GBs)(R_b) significantly increases after the C^+ implantation, and decreases with the increase in the annealing temperature(T_a) from 650℃ to 1000℃. This implies that the C^+ implantation has a more significant impact on the conductivity of GBs. Conductive atomic force microscopy demonstrates that the number of conductive sites increases in GB regions at T_a above 900℃, owing to the formation of a nanographitic phase confirmed by high-resolution transmission electronic microscopy. Visible-light Raman spectra show that resistive trans-polyacetylene oligomers desorb from GBs at T_a above 900℃, which leads to lower R_b of samples annealed at 900 and 1000℃. With the increase in T_a to 1000℃, diamond grains become smaller with longer GBs modified by a more ordered nanographitic phase, supplying more conductive sites and leading to a lower R_b.展开更多
Experimental investigation has been carried out for laser ignition and combustion of nanothermites based on aluminum and oxides of copper,bismuth and molybdenum.Ultrasonic mixing of nanosized powders was used to produ...Experimental investigation has been carried out for laser ignition and combustion of nanothermites based on aluminum and oxides of copper,bismuth and molybdenum.Ultrasonic mixing of nanosized powders was used to produce compositions.For thermite ignition,initiating laser pulse with a maximum intensity of 770 W/cm2 was generated by a laser diode with a wavelength of 808 nm.The ignition delay times,the minimum initiation energy density,and the average burning rate at various thermite densities and mass fractions of components were determined by recording the emission of radiation of the reaction products using a multichannel pyrometer jointly with a high-speed video camera.The effect of adding carbon black on the threshold parameters of a laser pulse was also studied.Based on the obtained results,certain assumptions were put forward with regard to the mechanism of nanothermites’ignition by laser radiation and their burning.In particular,the assumptions were made on the two-stage process of the reaction initiation and jet burning mechanism of porous nanothermites.展开更多
Nanofluids have great potential for solar energy harvesting due to their suitable optical and thermophysical properties.One of the promising applications of nanofluids is utilization in solar collectors with the direc...Nanofluids have great potential for solar energy harvesting due to their suitable optical and thermophysical properties.One of the promising applications of nanofluids is utilization in solar collectors with the direct absorption of light(DASC).The design of a DASC requires detailed knowledge of the optical properties of nanofluids,which can be significantly affected by the particle size distribution.The paper presents the method to take into account the particle size distribution when calculating nanofluid extinction spectra.To validate the proposed model,the particle size distribution and spectral absorbance were measured for aqueous suspension with multi-walled graphite nanotubes;the minimum size of primary nanoparticles was 49 nm.The proposed model is compared with experiments demonstrating the concentration averaged and maximum discrepancies of 6.6%and 32.2%against 12.6%and 77.7%for a model assuming a monosized suspension.展开更多
I.INTRODUCTION Strong interest in the modeling of planetary interiors,dwarf stars,and the physical conditions necessary to achieve inertial confinement fusion(ICF)have driven attention to the properties of matter at h...I.INTRODUCTION Strong interest in the modeling of planetary interiors,dwarf stars,and the physical conditions necessary to achieve inertial confinement fusion(ICF)have driven attention to the properties of matter at high density,temperature,and pressure(beyond the megabar limit).Extreme states of matter have been studied using gas guns,explosives,and Z-pinches,among other methods(see,e.g.,Refs.1–4).However in recent years,lasers have become the most reliable standard tool for creating extreme states of matter.展开更多
We examine the effect of laser focusing on the effectiveness of a recently discussed scheme[M.F.Ciappina et al.,Phys.Rev.A 99,043405(2019)and M.F.Ciappina and S.V.Popruzhenko,Laser Phys.Lett.17,025301(2020)]for in sit...We examine the effect of laser focusing on the effectiveness of a recently discussed scheme[M.F.Ciappina et al.,Phys.Rev.A 99,043405(2019)and M.F.Ciappina and S.V.Popruzhenko,Laser Phys.Lett.17,025301(2020)]for in situ determination of ultrahigh intensities of electromagnetic radiation delivered by multi-petawatt laser facilities.Using two model intensity distributions in the focus of a laser beam,we show how the resulting yields of highly charged ions generated in the process of multiple sequential tunneling of electrons from atoms depend on the shapes of these distributions.Our findings lead to the conclusion that an accurate extraction of the peak laser intensity can be made either in the near-threshold regime,when the production of the highest charge state happens only in a small part of the laser focus close to the point where the intensity is maximal or through the determination of the points where the ion yields of close charges become equal.We show that for realistic parameters of the gas target,the number of ions generated in the central part of the focus in the threshold regime should be sufficient for a reliable measurement with highly sensitive time-of-flight detectors.Although the positions of the intersection points generally depend on the focal shape,they can be used to localize the peak intensity value in certain intervals.Finally,the slope of the intensity-dependent ion yields is shown to be robust with respect to both the focal spot size and the spatial distribution of the laser intensity in the focus.When these slopes can be measured,they will provide the most accurate determination of the peak intensity value within the considered tunnel ionization scheme.In addition to this analysis,we discuss the method in comparison with other recently proposed approaches for direct measurement of extreme laser intensities.展开更多
On the basis of equations obtained in the framework of second-order quantum-mechanical perturbation theory,the standard approach to the calculation of scattering radiation probability is extended to the case of ultras...On the basis of equations obtained in the framework of second-order quantum-mechanical perturbation theory,the standard approach to the calculation of scattering radiation probability is extended to the case of ultrashort laser pulses.Weinvestigate the mechanism of the appearance of plasmon peaks in the spectrum of the plasma form factor for different parameters of the problem.For the case in which scattering on plasmons dominates over scattering on electron density fluctuations caused by chaotic thermal motion,we derive analytical expressions describing the scattering probability of ultrashort laser pulses on plasmons.Together with this,we obtain a simple expression connecting the frequency of scattered radiation and the energy transmitted from the incident pulse to plasmon,and vice versa.In considering the scattering probability,our emphasis is on the dependence on the pulse duration.Weassess in detail the trends of this dependence for various relations between pulse carrier frequency and plasmon energy.展开更多
基金supported by the Russian Science Foundation(Grant No.22-14-20001).
文摘In addition to their visible motion such as swimming(e.g.,with the help offlagella),bacteria can also exhibit nanomotion that is detectable only with highly sensitive instruments,and this study shows that it is possible to detect bacterial nanomotion using an AFM detection system.The results show that the nanomotion characteristics depend on the bacterial strain,and that nanomotion can be used to sense the metabolic activity of bacteria because the oscillations are sensitive to the food preferences of the bacteria and the type of surrounding medium.
基金supported by the Czech Academy of Sciences(Mobility Plus Project No.CNRS-23-12)A.M.F.was supported by the Russian Science Foundation(Grant No.20-12-00077).
文摘Coherent motion of particles in a plasma can imprint itself on radiation.The recent advent of high-power lasers—allowing the nonlinear inverse Compton-scattering regime to be reached—has opened the possibility of looking at collective effects in laser–plasma interactions.Under certain conditions,the collective interaction of many electrons with a laser pulse can generate coherent radiation in the hard x-ray regime.This perspective paper explains the limitations under which such a regime might be attained.
基金supported by the Czech Ministry of Education,Youth and Sports(Project No.CZ.02.2.69/0.0/0.0/18_053/0016980)the Grant Agency of the Czech Republic(Grant No.GM23-05027M).
文摘Directed x-rays produced in the interaction of sub-picosecond laser pulses of moderate relativistic intensity with plasma of near-critical density are investigated. Synchrotron-like (betatron) radiation occurs in the process of direct laser acceleration (DLA) of electrons in a relativisticlaser channel when the electrons undergo transverse betatron oscillations in self-generated quasi-static electric and magnetic fields. In anexperiment at the PHELIX laser system, high-current directed beams of DLA electrons with a mean energy ten times higher than the ponderomotive potential and maximum energy up to 100 MeV were measured at 10^(19) W/cm^(2)laser intensity. The spectrum of directed x-raysin the range of 5–60 keV was evaluated using two sets of Ross filters placed at 0°and 10°to the laser pulse propagation axis. The differential x-ray absorption method allowed for absolute measurements of the angular-dependent photon fluence. We report 10^(13) photons/sr withenergies >5 keV measured at 0°to the laser axis and a brilliance of 10^(21) photons s^(−1) mm^(−2) mrad−2(0.1%BW)−1. The angular distributionof the emission has an FWHM of 14°–16°. Thanks to the ultra-high photon fluence, point-like radiation source, and ultra-short emissiontime, DLA-based keV backlighters are promising for various applications in high-energy-density research with kilojoule petawatt-class laserfacilities.
基金supported by funding by the IAEA technical contracts within IAEA Coordinated Research Projects on‘Joint Research Using Small Tokamaks’and on‘Utilisation of a Network of Small Magnetic Confinement Fusion Devices for Mainstream Fusion Research’funded by Russian Science Foundation,Project 19-12-00312+3 种基金partly supported by the Competitiveness Program of NRNU MEPhIthe partial financial support from MEPhI and NRU MPEI in the framework of the Russian Academic Excellence Projectsupported by Tokamak Energy LtdOxford Instruments(UK)。
文摘Joint experiments(JEs)on small tokamaks have been regularly performed between 2005 and 2015 under the framework of the International Atomic Energy Agency(IAEA)coordinated research projects(CRPs).This paper describes the background and the rationale for these experiments,how they were organized and executed,main areas of research covered during these experiments,main results,contributions to mainstream fusion research,and discusses lessons learned and outcomes from these activities.We underline several of the most important scientific outputs and also specific outputs in the education of young scientists and scientists from developing countries and their importance.
基金supported by the Ministry of Science and Higher Education of the Russian Federation(Agreement No.075-15-2021-1361).
文摘Irradiation of a thin metallic wire with an intense femtosecond laser pulse creates a strong discharge wave that travels as a narrow pulse along the wire surface.This traveling discharge efficiently emits secondary radiation with spectral characteristics that are mostly defined by the wire geometry.Several examples of designs are considered here in the context of generation of intense terahertz radiation with controllable characteristics for various scientific and technological applications.The proposed setup may be easily realized,and it has the merits of robustness,versatility,and high conversion efficiency(reaching several percent)of laser energy to terahertz radiation.
基金supported by RFBR,ROSATOM(Grant No.20-21-00023)the Ministry of Science and Higher Education of the Russian Federation(Agreement No.075-15-2021-1361)+1 种基金the Foundation for the Advancement of Theoretical Physics and Mathematics(“BASIS”)for financial support(Grant No.22-1-3-28-1)partially supported by resources of the NRNU MEPhI High-Performance Computing Center.
文摘A neural network-based approach is proposed both for reconstructing the focal spot intensity profile and for estimating the peak intensity of a high-power tightly focused laser pulse using the angular energy distributions of protons accelerated by the pulse from rarefied gases.For these purposes,we use a convolutional neural network architecture.Training and testing datasets are calculated using the test particle method,with the laser description in the form of Stratton-Chu integrals,which model laser pulses focused by an off-axis parabolic mirror down to the diffraction limit.To demonstrate the power and robustness of this method,we discuss the reconstruction of axially symmetric intensity profiles for laser pulses with intensities and focal diameters in the ranges of 10^(21)-10^(23) W cm^(−2) and ~(1-4)λ,respectively.This approach has prospects for implementation at higher intensities and with asymmetric laser beams,and it can provide a valuable diagnostic method for emerging extremely intense laser facilities.
基金This work was carried out within the framework of the EUROfusion Consortium,funded by the European Union via the Euratom Research and Training Programme(Grant No.101052200-EUROfusion)Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union or the European Commission.Neither the European Union nor the European Commission can be held responsible for them.The involved teams have operated within the framework of the Enabling Research Project:Grant No.ENR-IFE.01.CEA“Advancing shock ignition for direct-drive inertial fusion.”The work was also supported by the Natural Sciences and Engineering Research Council of Canada(Grant No.RGPIN-2019-05013)+5 种基金The authors acknowledge support of the PALS Infrastructure within the MŠMT(MEYS)project Grant No.LM2023068Staff members of the PALS Research Center appreciate financial support(Grant No.LM2023068)from the Czech Ministry of Education,Youth and Sports facilitating operation of the PALS facilityThe work of JIHT RAS team was supported by the Ministry of Science and Higher Education of the Russian Federation(State Assignment No.075-01129-23-00)The work at NRMU MEPhI was supported by the Ministry of Science and Higher Education of the Russian Federation(Agreement No.075-15-2021-1361)This project has received funding from the CNR funded Italian research Network ELI-Italy(D.M.No.63108.08.2016)This work was funded by United Kingdom EPSRC Grants No.EP/P026796/1 and No.EP/L01663X/1.The results presented in this paper are based on work carried out between September 2018 and December 2021.
文摘In an experiment carried out at the Prague Asterix Laser System at laser intensities relevant to shock ignition conditions(I>10^(16) W/cm^(2)),the heating and transport of hot electrons were studied by using several complementary diagnostics,i.e.,K_(α)time-resolved imaging,hard x-ray filtering(a bremsstrahlung cannon),and electron spectroscopy.Ablators with differing composition from low Z(parylene N)to high Z(nickel)were used in multilayer planar targets to produce plasmas with different coronal temperature and collisionality and modify the conditions of hot-electron generation.The variety of available diagnostics allowed full characterization of the population of hot electrons,retrieving their conversion efficiency,time generation and duration,temperature,and angular divergence.The obtained results are shown to be consistent with those from detailed simulations and similar inertial confinement fusion experiments.Based on the measured data,the advantages,reliability,and complementarity of the experimental diagnostics are discussed.
文摘Based on the standard definition of the product (concatenation), the natural non-negative degree of the language is introduced. Root extraction is the reverse operation to it, and it can be defined in several different ways. Despite the simplicity of the formulation of the problem of extracting the root, the authors could not find any description of it in the literature (as well as on the Internet), including even its formulation. Most of the material in this article is devoted to the simplest version of the formulation: the root of the 2<sup>nd</sup> degree for the 1-letter alphabet, but many of the provisions of the article are generalized to more complex cases. Apparently, for a possible future description of a polynomial algorithm for solving at least one of the described statements of root extraction problems, it is first necessary to really analyze in detail such a special case, that is: either describe the necessary polynomial algorithm, or, conversely, show that the problem belongs to the class of NP-complete problems. Thus, in this article, we do not propose a polynomial algorithm for the problems under consideration;however, the models described here should help in constructing appropriate heuristic algorithms for their solution. A detailed description of the possible further application of such heuristic algorithms is beyond the scope of this article. .
基金support of the German BMBF is acknowledged for many supporting grants for PRIOR,cryo-target development,beam diagnostics and material properties researchthe support of DFGRFBR(German Science Foundation-Russian Foundation of Basic Research)+1 种基金the Russian grant of Scientific school НШ-5814.2014.2 is acknowledgedgrateful for funding from National Natural Science Foundation of China NSFC grants Nos.:U1532263,11505248,11375034,11205225,11275241,and 11275238.
文摘We review the development of High Energy Density Physics(HEDP)with intense heavy ion beams as a tool to induce extreme states of matter.The development of this field connects intimately to the advances in accelerator physics and technology.We will cover the generation of intense heavy ion beams starting from the ion source and follow the acceleration process and transport to the target.Intensity limitations and potential solutions to overcome these limitations are discussed.This is exemplified by citing examples from existing machines at the Gesellschaft fur Schwerionenforschung(GSI-Darmstadt),the Institute of Theoretical and Experimental Physics in Moscow(ITEP-Moscow),and the Institute of Modern Physics(IMP-Lanzhou).Facilities under construction like the FAIR facility in Darmstadt and the High Intensity Accelerator Facility(HIAF),proposed for China will be included.Developments elsewhere are covered where it seems appropriate along with a report of recent results and achievements.
基金supported by the Russian Ministry of Education and Science(RMES),Agreement No.14.613.21.0021,unique ID No.RFMEFI61314X0021the Department ofScience & Technology(DST),India,grant No.GAP0246 under the joint RMES-DST Research Collaboration Agreement 'Development of large size polycrystalline CVD diamond material for optical windows and support rods in high power microwave tubes'
文摘Polycrystalline diamond(PCD) films 100 mm in diameter are grown by 915 MHz microwave plasma chemical vapor deposition(MPCVD) at different process parameters,and their thermal conductivity(TC) is evaluated by a laser flash technique(LFT) in the temperature range of230-380 K.The phase purity and quality of the films are assessed by micro-Raman spectroscopy based on the diamond Raman peak width and the amorphous carbon(a-C) presence in the spectra.Decreasing and increasing dependencies for TC with temperature are found for high and low quality samples,respectively.TC,as high as 1950 ± 230 W m^(-1) K^(-1) at room temperature,is measured for the most perfect material.A linear correlation between the TC at room temperature and the fraction of the diamond component in the Raman spectrum for the films is established.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.50972129 and 50602039)the International Science Technology Cooperation Program of China(Grant No.2014DFR51160)+3 种基金the National Key Research and Development Program of China(Grant No.2016YFE0133200)European Union’s Horizon 2020 Research and Innovation Staff Exchange(RISE)Scheme(Grant No.734578)One Belt and One Road International Cooperation Project from the Key Research and Development Program of Zhejiang Province,China(Grant No.2018C04021)Xinmiao Talents Program of Zhejiang Province,China(Grant No.2017R403078)
文摘We investigate the structural and electrical properties of carbon-ion-implanted ultrananocrystalline diamond(UNCD)films. Impedance spectroscopy measurements show that the impedance of diamond grains is relatively stable, while that of grain boundaries(GBs)(R_b) significantly increases after the C^+ implantation, and decreases with the increase in the annealing temperature(T_a) from 650℃ to 1000℃. This implies that the C^+ implantation has a more significant impact on the conductivity of GBs. Conductive atomic force microscopy demonstrates that the number of conductive sites increases in GB regions at T_a above 900℃, owing to the formation of a nanographitic phase confirmed by high-resolution transmission electronic microscopy. Visible-light Raman spectra show that resistive trans-polyacetylene oligomers desorb from GBs at T_a above 900℃, which leads to lower R_b of samples annealed at 900 and 1000℃. With the increase in T_a to 1000℃, diamond grains become smaller with longer GBs modified by a more ordered nanographitic phase, supplying more conductive sites and leading to a lower R_b.
基金supported by a grant for large scientific projects in priority areas of scientific and technological development No.13.1902.21.0035carried out at Federal Research Center for Chemical Physics,Russian Academy of Sciences(FRC CP RAS),Russian Academy of Sciences(RAS)financially supported by subsidies for the implementation of the state assignment on the topic No.0082-2019-0016。
文摘Experimental investigation has been carried out for laser ignition and combustion of nanothermites based on aluminum and oxides of copper,bismuth and molybdenum.Ultrasonic mixing of nanosized powders was used to produce compositions.For thermite ignition,initiating laser pulse with a maximum intensity of 770 W/cm2 was generated by a laser diode with a wavelength of 808 nm.The ignition delay times,the minimum initiation energy density,and the average burning rate at various thermite densities and mass fractions of components were determined by recording the emission of radiation of the reaction products using a multichannel pyrometer jointly with a high-speed video camera.The effect of adding carbon black on the threshold parameters of a laser pulse was also studied.Based on the obtained results,certain assumptions were put forward with regard to the mechanism of nanothermites’ignition by laser radiation and their burning.In particular,the assumptions were made on the two-stage process of the reaction initiation and jet burning mechanism of porous nanothermites.
基金The reported study was funded by RFBR,Project No.19-38-90306.
文摘Nanofluids have great potential for solar energy harvesting due to their suitable optical and thermophysical properties.One of the promising applications of nanofluids is utilization in solar collectors with the direct absorption of light(DASC).The design of a DASC requires detailed knowledge of the optical properties of nanofluids,which can be significantly affected by the particle size distribution.The paper presents the method to take into account the particle size distribution when calculating nanofluid extinction spectra.To validate the proposed model,the particle size distribution and spectral absorbance were measured for aqueous suspension with multi-walled graphite nanotubes;the minimum size of primary nanoparticles was 49 nm.The proposed model is compared with experiments demonstrating the concentration averaged and maximum discrepancies of 6.6%and 32.2%against 12.6%and 77.7%for a model assuming a monosized suspension.
文摘I.INTRODUCTION Strong interest in the modeling of planetary interiors,dwarf stars,and the physical conditions necessary to achieve inertial confinement fusion(ICF)have driven attention to the properties of matter at high density,temperature,and pressure(beyond the megabar limit).Extreme states of matter have been studied using gas guns,explosives,and Z-pinches,among other methods(see,e.g.,Refs.1–4).However in recent years,lasers have become the most reliable standard tool for creating extreme states of matter.
基金support from the Russian Foundation for Basic Research via Grant No.19-02-00643.M.F.C.acknowledges the Spanish Ministry MINECO and State Research Agency AEI(FIDEUA PID2019-106901GB-I00/10.13039/501100011033,SEVERO OCHOA No.SEV-2015-0522,FPI)European Social Fund,Fundacio Cellex,Fundacio Mir-Puig,Generalitat de Catalunya(AGAUR Grant No.2017 SGR 1341,CERCA program,QuantumCATU16-011424,co-funded by ERDFOperational Program of Catalonia 2014-2020)+2 种基金MINECO-EU QUANTERA MAQS(funded by The State Research Agency(AEI)PCI2019-111828-2/10.13039/501100011033)the National Science Centre,Poland-Symfonia Grant No.2016/20/W/ST4/00314the project Advanced Research Using High Intensity Laser Produced Photons and Particles(Grant No.CZ.02.1.01/0.0/0.0/16_019/0000789)through the European Regional Development Fund(ADONIS).
文摘We examine the effect of laser focusing on the effectiveness of a recently discussed scheme[M.F.Ciappina et al.,Phys.Rev.A 99,043405(2019)and M.F.Ciappina and S.V.Popruzhenko,Laser Phys.Lett.17,025301(2020)]for in situ determination of ultrahigh intensities of electromagnetic radiation delivered by multi-petawatt laser facilities.Using two model intensity distributions in the focus of a laser beam,we show how the resulting yields of highly charged ions generated in the process of multiple sequential tunneling of electrons from atoms depend on the shapes of these distributions.Our findings lead to the conclusion that an accurate extraction of the peak laser intensity can be made either in the near-threshold regime,when the production of the highest charge state happens only in a small part of the laser focus close to the point where the intensity is maximal or through the determination of the points where the ion yields of close charges become equal.We show that for realistic parameters of the gas target,the number of ions generated in the central part of the focus in the threshold regime should be sufficient for a reliable measurement with highly sensitive time-of-flight detectors.Although the positions of the intersection points generally depend on the focal shape,they can be used to localize the peak intensity value in certain intervals.Finally,the slope of the intensity-dependent ion yields is shown to be robust with respect to both the focal spot size and the spatial distribution of the laser intensity in the focus.When these slopes can be measured,they will provide the most accurate determination of the peak intensity value within the considered tunnel ionization scheme.In addition to this analysis,we discuss the method in comparison with other recently proposed approaches for direct measurement of extreme laser intensities.
基金funded by MIPT in the framework of the 5-Top-100 Programsupported by RFBR,Project No.19-32-90016.
文摘On the basis of equations obtained in the framework of second-order quantum-mechanical perturbation theory,the standard approach to the calculation of scattering radiation probability is extended to the case of ultrashort laser pulses.Weinvestigate the mechanism of the appearance of plasmon peaks in the spectrum of the plasma form factor for different parameters of the problem.For the case in which scattering on plasmons dominates over scattering on electron density fluctuations caused by chaotic thermal motion,we derive analytical expressions describing the scattering probability of ultrashort laser pulses on plasmons.Together with this,we obtain a simple expression connecting the frequency of scattered radiation and the energy transmitted from the incident pulse to plasmon,and vice versa.In considering the scattering probability,our emphasis is on the dependence on the pulse duration.Weassess in detail the trends of this dependence for various relations between pulse carrier frequency and plasmon energy.