The use of plasmas provides a way to overcome the low damage threshold of classical solid-state based optical materials,which is the main limitation encountered in producing and manipulating intense and energetic lase...The use of plasmas provides a way to overcome the low damage threshold of classical solid-state based optical materials,which is the main limitation encountered in producing and manipulating intense and energetic laser pulses.Plasmas can directly amplify or alter the characteristics of ultra-short laser pulses via the three-wave coupling equations for parametric processes.The strong-coupling regime of Brillouin scattering(sc-SBS)is of particular interest:recent progress in this domain is presented here.This includes the role of the global phase in the spatio-temporal evolution of the three-wave coupled equations for backscattering that allows a description of the coupling dynamics and the various stages of amplification from the initial growth to the so-called self-similar regime.The understanding of the phase evolution allows control of the directionality of the energy transfer via the phase relation between the pulses.A scheme that exploits this coupling in order to use the plasma as a wave plate is also suggested.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
High-energyγ-photon generation via nonlinear Compton scattering and electron–positron pair creation via the Breit–Wheeler process driven by laser–plasma interaction are modeled,and a number of mechanisms are propo...High-energyγ-photon generation via nonlinear Compton scattering and electron–positron pair creation via the Breit–Wheeler process driven by laser–plasma interaction are modeled,and a number of mechanisms are proposed.Owing to the small cross section,these processes require both an ultra-intense laser field and a relativistic electron bunch.The extreme conditions for such scenarios can be achieved through recent developments in laser technology.Photon emission via nonlinear Thomson and Compton scattering has been observed experimentally.Highenergy positron beams generated via a multiphoton process have recently been observed too.This paper reviews the principles ofγ-ray emission and e+e−pair creation in the context of laser–plasma interaction.Several proposed experimental setups forγ-ray emission and e+e−pair creation by ultra-intense laser pulses are compared in terms of their efficiency and the quality of theγ-photon and positron beams produced for ultrashort(15 fs)and longer(150 fs)multi-petawatt laser beams.展开更多
The role of the coronal electron plasma temperature for shock-ignition conditions is analysed with respect to the dominant parametric processes: stimulated Brillouin scattering, stimulated Raman scattering, two-plasmo...The role of the coronal electron plasma temperature for shock-ignition conditions is analysed with respect to the dominant parametric processes: stimulated Brillouin scattering, stimulated Raman scattering, two-plasmon decay(TPD), Langmuir decay instability(LDI) and cavitation. TPD instability and cavitation are sensitive to the electron temperature. At the same time the reflectivity and high-energy electron production are strongly affected. For low plasma temperatures the LDI plays a dominant role in the TPD saturation. An understanding of laser–plasma interaction in the context of shock ignition is an important issue due to the localization of energy deposition by collective effects and hot electron production.This in turn can have consequences for the compression phase and the resulting gain factor of the implosion phase.展开更多
Diagnosing the evolution of laser-generated high energy density(HED)systems is fundamental to develop a correct understanding of the behavior of matter under extreme conditions.Talbot–Lau interferometry constitutes a...Diagnosing the evolution of laser-generated high energy density(HED)systems is fundamental to develop a correct understanding of the behavior of matter under extreme conditions.Talbot–Lau interferometry constitutes a promising tool,since it permits simultaneous single-shot X-ray radiography and phase-contrast imaging of dense plasmas.We present the results of an experiment at OMEGA EP that aims to probe the ablation front of a laser-irradiated foil using a Talbot–Lau X-ray interferometer.A polystyrene(CH)foil was irradiated by a laser of 133 J,1 ns and probed with 8 keV laser-produced backlighter radiation from Cu foils driven by a short-pulse laser(153 J,11 ps).The ablation front interferograms were processed in combination with a set of reference images obtained ex situ using phase-stepping.We managed to obtain attenuation and phase-shift images of a laser-irradiated foil for electron densities above 1022 cm−3.These results showcase the capabilities of Talbot–Lau X-ray diagnostic methods to diagnose HED laser-generated plasmas through high-resolution imaging.展开更多
Photocatalytic reduction of CO2 by water was performed in the presence of a Ag/TiO2 catalyst under illumination by lamps with different wavelengths(254,365,and 400 nm).The yields of the main products(methane and metha...Photocatalytic reduction of CO2 by water was performed in the presence of a Ag/TiO2 catalyst under illumination by lamps with different wavelengths(254,365,and 400 nm).The yields of the main products(methane and methanol)were higher with the 254 nm lamp than with the 365 lamp while no products were observed with the 400 nm lamp.This was because the electron-hole generation rate increased with increasing energy of irradiation(decreasing wavelength)and there were higher densities of electron states at higher energies in TiO2. The increased efficiency of electron-hole generation with a shorter wavelength irradiation increased the efficiency of the catalyst.The energy of the electrons excited by visible light(400 nm)was too low for CO2 photocatalytic reduction.展开更多
A new near-infrared direct acceleration mechanism driven by Laguerre-Gaussian laser is proposed to stably accelerate and concentrate electron slice both in longitudinal and transversal directions in vacuum.Three-dimen...A new near-infrared direct acceleration mechanism driven by Laguerre-Gaussian laser is proposed to stably accelerate and concentrate electron slice both in longitudinal and transversal directions in vacuum.Three-dimensional simulations show that a 2-μm circularly polarized LG_(p)^(l)(p=0,l=1,σ_(2)=-1)laser can directly manipulate attosecond electron slices in additional dimensions(angular directions)and give them annular structures and angular momentums.These annular vortex attosecond electron slices are expected to have some novel applications such as in the collimation of antiprotons in conventional linear accelerators,edge-enhancement electron imaging,structured X-ray generation,and analysis and manipulation of nanomaterials.展开更多
The paper presents a review of dynamic stabilization mechanisms for plasma instabilities. One of the dynamic stabilization mechanisms for plasma instability was proposed in the paper [Kawata, Phys. Plasmas 19, 024503(...The paper presents a review of dynamic stabilization mechanisms for plasma instabilities. One of the dynamic stabilization mechanisms for plasma instability was proposed in the paper [Kawata, Phys. Plasmas 19, 024503(2012)],based on a perturbation phase control. In general, instabilities emerge from the perturbations. Normally the perturbation phase is unknown, and so the instability growth rate is discussed. However, if the perturbation phase is known, the instability growth can be controlled by a superimposition of perturbations imposed actively. Based on this mechanism we present the application results of the dynamic stabilization mechanism to the Rayleigh–Taylor instability(RTI) and to the filamentation instability as typical examples in this paper. On the other hand, in the paper [Boris, Comments Plasma Phys. Control. Fusion 3, 1(1977)] another mechanism was proposed to stabilize RTI, and was realized by the pulse train or the laser intensity modulation in laser inertial fusion [Betti et al., Phys. Rev. Lett. 71, 3131(1993)]. In this latter mechanism, an oscillating strong force is applied to modify the basic equation, and consequently the new stabilization window is created. Originally the latter was proposed by Kapitza. We review the two stabilization mechanisms, and present the application results of the former dynamic stabilization mechanism.展开更多
The study of structure, thermodynamic state, equation of state(EOS) and transport properties of warm dense matter(WDM) has become one of the key aspects of laboratory astrophysics. This field has demonstrated its impo...The study of structure, thermodynamic state, equation of state(EOS) and transport properties of warm dense matter(WDM) has become one of the key aspects of laboratory astrophysics. This field has demonstrated its importance not only concerning the internal structure of planets, but also other astrophysical bodies such as brown dwarfs, crusts of old stars or white dwarf stars. There has been a rapid increase in interest and activity in this field over the last two decades owing to many technological advances including not only the commissioning of high energy optical laser systems, zpinches and X-ray free electron lasers, but also short-pulse laser facilities capable of generation of novel particle and X-ray sources. Many new diagnostic methods have been developed recently to study WDM in its full complexity. Even ultrafast nonequilibrium dynamics has been accessed for the first time thanks to subpicosecond laser pulses achieved at new facilities. Recent years saw a number of major discoveries with direct implications to astrophysics such as the formation of diamond at pressures relevant to interiors of frozen giant planets like Neptune, metallic hydrogen under conditions such as those found inside Jupiter’s dynamo or formation of lonsdaleite crystals under extreme pressures during asteroid impacts on celestial bodies. This paper provides a broad review of the most recent experimental work carried out in this field with a special focus on the methods used. All typical schemes used to produce WDM are discussed in detail. Most of the diagnostic techniques recently established to probe WDM are also described. This paper also provides an overview of the most prominent examples of these methods used in experiments. Even though the main emphasis of the publication is experimental work focused on laboratory astrophysics primarily at laser facilities, a brief outline of other methods such as dynamic compression with z-pinches and static compression using diamond anvil cells(DAC) is also included. Some relevant theoretical and computational efforts related to WDM and astrophysics are mentioned in this review.展开更多
The co-existence of the Raman and Brillouin backscattering instability is an important issue for inertial confinement fusion. The present paper presents extensive one-dimensional(1D) particle-in-cell(PIC) simulations ...The co-existence of the Raman and Brillouin backscattering instability is an important issue for inertial confinement fusion. The present paper presents extensive one-dimensional(1D) particle-in-cell(PIC) simulations for a wide range of parameters extending and complementing previous findings. PIC simulations show that the scenario of reflectivity evolution and saturation is very sensitive to the temperatures, intensities, size of plasma and boundary conditions employed. The Langmuir decay instability is observed for rather small k_(epw)λ_D but has no influence on the saturation of Brillouin backscattering, although there is a clear correlation of Langmuir decay instability modes and ion-fractional decay for certain parameter ranges. Raman backscattering appears at any intensity and temperature but is only a transient phenomenon. In several configurations forward as well as backward Raman scattering is observed. For the intensities considered, I λ_o^2 above 10^(15) W μm^2/cm^2, Raman is always of bursty nature. A particular setup allows the simulation of multi-speckle aspects in which case it is found that Raman is self-limiting due to strong modifications of the distribution function. Kinetic effects are of prime importance for Raman backscattering at high temperatures. No unique scenario for the saturation of Raman scattering or Raman–Brillouin competition does exist. The main effect in the considered parameter range is pump depletion because of large Brillouin backscattering. However, in the low k_(epw)λ_D regime the presence of ion-acoustic waves due to the Langmuir decay instability from the Raman created electron plasma waves can seed the ion-fractional decay and affect the Brillouin saturation.展开更多
Technology based on high-peak-power lasers has the potential to provide compact and intense radiation sources for a wide range of innovative applications.In particular,electrons that are accelerated in the wakefield o...Technology based on high-peak-power lasers has the potential to provide compact and intense radiation sources for a wide range of innovative applications.In particular,electrons that are accelerated in the wakefield of an intense laser pulse oscillate around the propagation axis and emit X-rays.This betatron source,which essentially reproduces the principle of a synchrotron at the millimeter scale,provides bright radiation with femtosecond duration and high spatial coherence.However,despite its unique features,the usability of the betatron source has been constrained by its poor control and stability.In this article,we demonstrate the reliable production of X-ray beams with tunable polarization.Using ionization-induced injection in a gas mixture,the orbits of the relativistic electrons emitting the radiation are reproducible and controlled.We observe that both the signal and beam profile fluctuations are significantly reduced and that the beam pointing varies by less than a tenth of the beam divergence.The polarization ratio reaches 80%,and the polarization axis can easily be rotated.We anticipate a broad impact of the source,as its unprecedented performance opens the way for new applications.展开更多
Fast magnetic field annihilation in a collisionless plasma is induced by using TEM(1,0) laser pulse. The magnetic quadrupole structure formation, expansion and annihilation stages are demonstrated with 2.5-dimensional...Fast magnetic field annihilation in a collisionless plasma is induced by using TEM(1,0) laser pulse. The magnetic quadrupole structure formation, expansion and annihilation stages are demonstrated with 2.5-dimensional particle-in-cell simulations. The magnetic field energy is converted to the electric field and accelerate the particles inside the annihilation plane. A bunch of high energy electrons moving backwards is detected in the current sheet. The strong displacement current is the dominant contribution which induces the longitudinal inductive electric field.展开更多
Strain-engineered silicon nanocrystals(SiNCs)have recently been shown to possess direct bandgap.Here,we report the observation of a rich structure in the single-nanocrystal photoluminescence spectra of strain-engineer...Strain-engineered silicon nanocrystals(SiNCs)have recently been shown to possess direct bandgap.Here,we report the observation of a rich structure in the single-nanocrystal photoluminescence spectra of strain-engineered direct-bandgap SiNCs in the temperature range of 9–300 K.The relationship between individual types of spectra is discussed,and the numerical modeling of spectral diffusion of the experimentally acquired spectra reveals a common origin for most types.The intrinsic spectral shape is shown to be a structure that contains three peaks,approximately 150 meV apart,each of which possesses a Si phonon substructure.Narrow spectral lines,reaching ≤ meV at 20 K,are detected.The observed temperature dependence of the spectral structure can be assigned to the radiative recombination of positively charged trions,in contrast to several previous reports linking a very similar shape to phonons in the surface capping layers.Our result serves as strong additional support for the direct-bandgap nature of the investigated SiNCs.展开更多
Magnetic reconnection driven by laser plasma interactions attracts great interests in the recent decades. Motivated by the rapid development of the laser technology, the ultra strong magnetic field generated by the la...Magnetic reconnection driven by laser plasma interactions attracts great interests in the recent decades. Motivated by the rapid development of the laser technology, the ultra strong magnetic field generated by the laser-plasma accelerated electrons provides unique environment to investigate the relativistic magnetic field annihilation and reconnection. It opens a new way for understanding relativistic regimes of fast magnetic field dissipation particularly in space plasmas,where the large scale magnetic field energy is converted to the energy of the nonthermal charged particles. Here we review the recent results in relativistic magnetic reconnection based on the laser and collisionless plasma interactions.The basic mechanism and the theoretical model are discussed. Several proposed experimental setups for relativistic reconnection research are presented.展开更多
基金This work has been done within the LABEX Plas@par project,and received financial state aid managed by the Agence Nationale de la Recherche,as part of the program“Investissements d’avenir”under the reference ANR-11-IDEX-0004-02.H.P.acknowledges the funding from China Scholarship Council.S.W.was supported by the project Advanced research using high intensity laser produced photons and particles(ADONIS)(CZ.02.1.01/0.0/0.0/16_019/0000789)from the European Regional Development Fund and by the project High Field Initiative(HiFI)(CZ.02.1.01/0.0/0.0/15_003/0000449)from the European Regional Development Fund.
文摘The use of plasmas provides a way to overcome the low damage threshold of classical solid-state based optical materials,which is the main limitation encountered in producing and manipulating intense and energetic laser pulses.Plasmas can directly amplify or alter the characteristics of ultra-short laser pulses via the three-wave coupling equations for parametric processes.The strong-coupling regime of Brillouin scattering(sc-SBS)is of particular interest:recent progress in this domain is presented here.This includes the role of the global phase in the spatio-temporal evolution of the three-wave coupled equations for backscattering that allows a description of the coupling dynamics and the various stages of amplification from the initial growth to the so-called self-similar regime.The understanding of the phase evolution allows control of the directionality of the energy transfer via the phase relation between the pulses.A scheme that exploits this coupling in order to use the plasma as a wave plate is also suggested.
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This work was supported by the projects ELITAS(No.CZ.02.1.01/0.0/0.0/16_013/0001793)High Field Initiative(No.CZ.02.1.01/0.0/0.0/15_003/0000449)+1 种基金both from the European Regional Development Fund.It was also supported by the project ADONIS(Advanced Research Using High Intensity Laser Produced Photons and Particles),No.CZ.02.1.01/0.0/0.0/16_019/0000789from the European Regional Development Fund.The support of Czech Science Foundation Project No.18-09560S is acknowledged.Computational resources were provided by the MetaCentrum under the Program No.LM2010005,by the IT4Innovations Centre of Excellence under the Project Nos.CZ.1.05/1.1.00/02.0070 and LM2011033,and by the ECLIPSE cluster of ELI-Beamlines.The EPOCH code was developed as part of the UKEPSRC-funded Project No.EP/G054940/1.
文摘High-energyγ-photon generation via nonlinear Compton scattering and electron–positron pair creation via the Breit–Wheeler process driven by laser–plasma interaction are modeled,and a number of mechanisms are proposed.Owing to the small cross section,these processes require both an ultra-intense laser field and a relativistic electron bunch.The extreme conditions for such scenarios can be achieved through recent developments in laser technology.Photon emission via nonlinear Thomson and Compton scattering has been observed experimentally.Highenergy positron beams generated via a multiphoton process have recently been observed too.This paper reviews the principles ofγ-ray emission and e+e−pair creation in the context of laser–plasma interaction.Several proposed experimental setups forγ-ray emission and e+e−pair creation by ultra-intense laser pulses are compared in terms of their efficiency and the quality of theγ-photon and positron beams produced for ultrashort(15 fs)and longer(150 fs)multi-petawatt laser beams.
基金support from grant ANR-11-IDEX-0004-02 Plas@Parthe support of the Czech Science Foundation (Project No. CZ.1.07/2.3.00/20.0279)ELI (Project No. CZ.1.05/1.1.00/02.0061)
文摘The role of the coronal electron plasma temperature for shock-ignition conditions is analysed with respect to the dominant parametric processes: stimulated Brillouin scattering, stimulated Raman scattering, two-plasmon decay(TPD), Langmuir decay instability(LDI) and cavitation. TPD instability and cavitation are sensitive to the electron temperature. At the same time the reflectivity and high-energy electron production are strongly affected. For low plasma temperatures the LDI plays a dominant role in the TPD saturation. An understanding of laser–plasma interaction in the context of shock ignition is an important issue due to the localization of energy deposition by collective effects and hot electron production.This in turn can have consequences for the compression phase and the resulting gain factor of the implosion phase.
基金supported by the National Nuclear Security Administration (DENA0003882)funding from the Conseil Règional Aquitaine (INTALAX)+1 种基金the Agence Nationale de la Recherche (ANR-10-IDEX-03-02, ANR-15CE30-0011)supported by Research Grant No. PID2019-108764RB-I00 from the Spanish Ministry of Science and Innovation
文摘Diagnosing the evolution of laser-generated high energy density(HED)systems is fundamental to develop a correct understanding of the behavior of matter under extreme conditions.Talbot–Lau interferometry constitutes a promising tool,since it permits simultaneous single-shot X-ray radiography and phase-contrast imaging of dense plasmas.We present the results of an experiment at OMEGA EP that aims to probe the ablation front of a laser-irradiated foil using a Talbot–Lau X-ray interferometer.A polystyrene(CH)foil was irradiated by a laser of 133 J,1 ns and probed with 8 keV laser-produced backlighter radiation from Cu foils driven by a short-pulse laser(153 J,11 ps).The ablation front interferograms were processed in combination with a set of reference images obtained ex situ using phase-stepping.We managed to obtain attenuation and phase-shift images of a laser-irradiated foil for electron densities above 1022 cm−3.These results showcase the capabilities of Talbot–Lau X-ray diagnostic methods to diagnose HED laser-generated plasmas through high-resolution imaging.
基金supported by the Czech Ministry of Education,Youth and Sports(research project LA08050)the Grant Agency of theCzech Republic(GA 104/09/0694)
文摘Photocatalytic reduction of CO2 by water was performed in the presence of a Ag/TiO2 catalyst under illumination by lamps with different wavelengths(254,365,and 400 nm).The yields of the main products(methane and methanol)were higher with the 254 nm lamp than with the 365 lamp while no products were observed with the 400 nm lamp.This was because the electron-hole generation rate increased with increasing energy of irradiation(decreasing wavelength)and there were higher densities of electron states at higher energies in TiO2. The increased efficiency of electron-hole generation with a shorter wavelength irradiation increased the efficiency of the catalyst.The energy of the electrons excited by visible light(400 nm)was too low for CO2 photocatalytic reduction.
基金supported by the National Natural Science Foundation of China(grant number 12075306)Strategic Priority Research Program of the Chinese Academy of Sciences(grant number XDB16010600)+4 种基金Key Research Programs in Frontier Science(grant number ZDBSLY-SLH006)Shanghai special science and technology innovation supported project(grant number 2019-jmrh1-kj1)Advanced research using high-intensity laser-produced photons and particles(ADONISgrant number CZ.02.1.01/0.0/0.0/16019/0000789)and High Field Initiative(HiFI,grant number CZ.02.1.01/0.0/0.0/15003/0000449)financial support of the Ministry of Education,Youth and Sports as part of targeted support from the National Programme of Sustainability Ⅱ。
文摘A new near-infrared direct acceleration mechanism driven by Laguerre-Gaussian laser is proposed to stably accelerate and concentrate electron slice both in longitudinal and transversal directions in vacuum.Three-dimensional simulations show that a 2-μm circularly polarized LG_(p)^(l)(p=0,l=1,σ_(2)=-1)laser can directly manipulate attosecond electron slices in additional dimensions(angular directions)and give them annular structures and angular momentums.These annular vortex attosecond electron slices are expected to have some novel applications such as in the collimation of antiprotons in conventional linear accelerators,edge-enhancement electron imaging,structured X-ray generation,and analysis and manipulation of nanomaterials.
基金supported by MEXTJSPS Kakenhi15K05359+8 种基金ILE/Osaka UniversityCORE/Utsunomiya UniversityJapan–U.S.Fusion Research Collaboration Program conducted by MEXT,Japansupported by the project ELITAS(CZ.02.1.01/0.0/0.0/16 013/0001793)the project High Field Initiative(CZ.02.1.01/0.0/0.0/15 003/0000449)both from European Regional Development Fundfunding from the European Union’s Horizon2020 research and innovation programme under grant agreement No.633053(EURO fusion project CfP-AWP17-IFE-CEA-01)the IT4Innovations Centre of Excellence under projects CZ.1.05/1.1.00/02.0070 and LM2011033ECLIPSE cluster of ELI-BeamlinesUK EPSRC funded projects EP/G054940/1
文摘The paper presents a review of dynamic stabilization mechanisms for plasma instabilities. One of the dynamic stabilization mechanisms for plasma instability was proposed in the paper [Kawata, Phys. Plasmas 19, 024503(2012)],based on a perturbation phase control. In general, instabilities emerge from the perturbations. Normally the perturbation phase is unknown, and so the instability growth rate is discussed. However, if the perturbation phase is known, the instability growth can be controlled by a superimposition of perturbations imposed actively. Based on this mechanism we present the application results of the dynamic stabilization mechanism to the Rayleigh–Taylor instability(RTI) and to the filamentation instability as typical examples in this paper. On the other hand, in the paper [Boris, Comments Plasma Phys. Control. Fusion 3, 1(1977)] another mechanism was proposed to stabilize RTI, and was realized by the pulse train or the laser intensity modulation in laser inertial fusion [Betti et al., Phys. Rev. Lett. 71, 3131(1993)]. In this latter mechanism, an oscillating strong force is applied to modify the basic equation, and consequently the new stabilization window is created. Originally the latter was proposed by Kapitza. We review the two stabilization mechanisms, and present the application results of the former dynamic stabilization mechanism.
基金supported by the Helmholtz Association under VH-NG1338
文摘The study of structure, thermodynamic state, equation of state(EOS) and transport properties of warm dense matter(WDM) has become one of the key aspects of laboratory astrophysics. This field has demonstrated its importance not only concerning the internal structure of planets, but also other astrophysical bodies such as brown dwarfs, crusts of old stars or white dwarf stars. There has been a rapid increase in interest and activity in this field over the last two decades owing to many technological advances including not only the commissioning of high energy optical laser systems, zpinches and X-ray free electron lasers, but also short-pulse laser facilities capable of generation of novel particle and X-ray sources. Many new diagnostic methods have been developed recently to study WDM in its full complexity. Even ultrafast nonequilibrium dynamics has been accessed for the first time thanks to subpicosecond laser pulses achieved at new facilities. Recent years saw a number of major discoveries with direct implications to astrophysics such as the formation of diamond at pressures relevant to interiors of frozen giant planets like Neptune, metallic hydrogen under conditions such as those found inside Jupiter’s dynamo or formation of lonsdaleite crystals under extreme pressures during asteroid impacts on celestial bodies. This paper provides a broad review of the most recent experimental work carried out in this field with a special focus on the methods used. All typical schemes used to produce WDM are discussed in detail. Most of the diagnostic techniques recently established to probe WDM are also described. This paper also provides an overview of the most prominent examples of these methods used in experiments. Even though the main emphasis of the publication is experimental work focused on laboratory astrophysics primarily at laser facilities, a brief outline of other methods such as dynamic compression with z-pinches and static compression using diamond anvil cells(DAC) is also included. Some relevant theoretical and computational efforts related to WDM and astrophysics are mentioned in this review.
基金support from grant ANR-11-IDEX-0004-02 Plas@Parsupport from the project ELI:Extreme Light Infrastructure (CZ.02.1.01/0.0/ 0.0/15-008/0000162) from European Regional Development
文摘The co-existence of the Raman and Brillouin backscattering instability is an important issue for inertial confinement fusion. The present paper presents extensive one-dimensional(1D) particle-in-cell(PIC) simulations for a wide range of parameters extending and complementing previous findings. PIC simulations show that the scenario of reflectivity evolution and saturation is very sensitive to the temperatures, intensities, size of plasma and boundary conditions employed. The Langmuir decay instability is observed for rather small k_(epw)λ_D but has no influence on the saturation of Brillouin backscattering, although there is a clear correlation of Langmuir decay instability modes and ion-fractional decay for certain parameter ranges. Raman backscattering appears at any intensity and temperature but is only a transient phenomenon. In several configurations forward as well as backward Raman scattering is observed. For the intensities considered, I λ_o^2 above 10^(15) W μm^2/cm^2, Raman is always of bursty nature. A particular setup allows the simulation of multi-speckle aspects in which case it is found that Raman is self-limiting due to strong modifications of the distribution function. Kinetic effects are of prime importance for Raman backscattering at high temperatures. No unique scenario for the saturation of Raman scattering or Raman–Brillouin competition does exist. The main effect in the considered parameter range is pump depletion because of large Brillouin backscattering. However, in the low k_(epw)λ_D regime the presence of ion-acoustic waves due to the Langmuir decay instability from the Raman created electron plasma waves can seed the ion-fractional decay and affect the Brillouin saturation.
基金the Agence Nationale pour la Recherche through the FENICS Project No.ANR-12-JS04-0004-01the Agence Nationale pour la Recherche through the FEMTOMAT Project No.ANR-13-BS04-0002+4 种基金the X-Five project(Contract No.339128)the LUCELX project(ANR-13-BS04-0011)the EuCARD2/ANAC2 EC FP7 project(Contract No.312453)the GARC project 15-03118Ssupport from the European Union’s Horizon 2020 research and innovation program under Grant Agreement No.654148 Laserlab-Europe.
文摘Technology based on high-peak-power lasers has the potential to provide compact and intense radiation sources for a wide range of innovative applications.In particular,electrons that are accelerated in the wakefield of an intense laser pulse oscillate around the propagation axis and emit X-rays.This betatron source,which essentially reproduces the principle of a synchrotron at the millimeter scale,provides bright radiation with femtosecond duration and high spatial coherence.However,despite its unique features,the usability of the betatron source has been constrained by its poor control and stability.In this article,we demonstrate the reliable production of X-ray beams with tunable polarization.Using ionization-induced injection in a gas mixture,the orbits of the relativistic electrons emitting the radiation are reproducible and controlled.We observe that both the signal and beam profile fluctuations are significantly reduced and that the beam pointing varies by less than a tenth of the beam divergence.The polarization ratio reaches 80%,and the polarization axis can easily be rotated.We anticipate a broad impact of the source,as its unprecedented performance opens the way for new applications.
基金supported by the project ELI:Extreme Light Infrastructure(CZ.02.1.01/0.0/0.0/15-008/0000162)from European Regional Development
文摘Fast magnetic field annihilation in a collisionless plasma is induced by using TEM(1,0) laser pulse. The magnetic quadrupole structure formation, expansion and annihilation stages are demonstrated with 2.5-dimensional particle-in-cell simulations. The magnetic field energy is converted to the electric field and accelerate the particles inside the annihilation plane. A bunch of high energy electrons moving backwards is detected in the current sheet. The strong displacement current is the dominant contribution which induces the longitudinal inductive electric field.
基金Czech Science Foundation Funding(Grant Nos.GPP204/12/P235(Katerina Kusova)and P108/12/G108(Ivan Pelant))and a L’Oreal-UNESCO for Women in Science scholarship(Katerina Kusova)are gratefully acknowledgedPart of this work was supported by the Czech-Japan collaborative project LG14246(Jan Valenta).
文摘Strain-engineered silicon nanocrystals(SiNCs)have recently been shown to possess direct bandgap.Here,we report the observation of a rich structure in the single-nanocrystal photoluminescence spectra of strain-engineered direct-bandgap SiNCs in the temperature range of 9–300 K.The relationship between individual types of spectra is discussed,and the numerical modeling of spectral diffusion of the experimentally acquired spectra reveals a common origin for most types.The intrinsic spectral shape is shown to be a structure that contains three peaks,approximately 150 meV apart,each of which possesses a Si phonon substructure.Narrow spectral lines,reaching ≤ meV at 20 K,are detected.The observed temperature dependence of the spectral structure can be assigned to the radiative recombination of positively charged trions,in contrast to several previous reports linking a very similar shape to phonons in the surface capping layers.Our result serves as strong additional support for the direct-bandgap nature of the investigated SiNCs.
基金supported by the project High Field Initiative(CZ.02.1.01/0.0/0.0/15003/0000449)from European Regional Development Fundby AFOSR(Grant No.FA9550-17-1-0382)。
文摘Magnetic reconnection driven by laser plasma interactions attracts great interests in the recent decades. Motivated by the rapid development of the laser technology, the ultra strong magnetic field generated by the laser-plasma accelerated electrons provides unique environment to investigate the relativistic magnetic field annihilation and reconnection. It opens a new way for understanding relativistic regimes of fast magnetic field dissipation particularly in space plasmas,where the large scale magnetic field energy is converted to the energy of the nonthermal charged particles. Here we review the recent results in relativistic magnetic reconnection based on the laser and collisionless plasma interactions.The basic mechanism and the theoretical model are discussed. Several proposed experimental setups for relativistic reconnection research are presented.
