The interaction of high-power laser pulses with undercritical foams produced by different techniques but with the same average density is studied at the PALS laser facility.The spatial-temporal evolution of X-ray emis...The interaction of high-power laser pulses with undercritical foams produced by different techniques but with the same average density is studied at the PALS laser facility.The spatial-temporal evolution of X-ray emission is observed using an X-ray streak camera,electron and ion temperatures are measured by X-ray spectroscopy,and hot-electron production is characterized by monochromatic X-ray imaging.Transmission of a femtosecond laser probe pulse through foams is observed in the near and far fields.In spite of large differences in pore size and foam structure,the velocity of ionization front propagation is quite similar for all the foams studied and is slower than that in a homogeneous material of the same average density.The ion temperature in the plasma behind the ionization front is a few times higher than the electron temperature.Hot-electron production in plastic foams with small pores is strongly suppressed compared with that in solid targets,whereas in foams produced by additive manufacturing,it is significantly increased to the level observed in bare copper foil targets.展开更多
The physics of laser-plasma interaction is studied on the Shenguang III prototype laser facility under conditions relevant to inertial confinement fusion designs.A sub-millimeter-size underdense hot plasma is created ...The physics of laser-plasma interaction is studied on the Shenguang III prototype laser facility under conditions relevant to inertial confinement fusion designs.A sub-millimeter-size underdense hot plasma is created by ionization of a low-density plastic foam by four high-energy(3.2 kJ)laser beams.An interaction beam is fired with a delay permitting evaluation of the excitation of parametric instabilities at different stages of plasma evolution.Multiple diagnostics are used for plasma characterization,scattered radiation,and accelerated electrons.The experimental results are analyzed with radiation hydrodynamic simulations that take account of foam ionization and homogenization.The measured level of stimulated Raman scattering is almost one order of magnitude larger than that measured in experiments with gasbags and hohlraums on the same installation,possibly because of a greater plasma density.Notable amplification is achieved in high-intensity speckles,indicating the importance of implementing laser temporal smoothing techniques with a large bandwidth for controlling laser propagation and absorption.展开更多
Comprehensive understanding and possible control of parametric instabilities in the context of inertial confinement fusion (ICF) remains achallenging task. The details of the absorption processes and the detrimental e...Comprehensive understanding and possible control of parametric instabilities in the context of inertial confinement fusion (ICF) remains achallenging task. The details of the absorption processes and the detrimental effects of hot electrons on the implosion process require as mucheffort on the experimental side as on the theoretical and simulation side. This paper describes a proposal for experimental studies on nonlinearinteraction of intense laser pulses with a high-temperature plasma under conditions corresponding to direct-drive ICF schemes. We propose todevelop a platform for laser-plasma interaction studies based on foam targets. Parametric instabilities are sensitive to the bulk plasma temperatureand the density scale length. Foam targets are sufficiently flexible to allow control of these parameters. However, investigationsconducted on small laser facilities cannot be extrapolated in a reliable way to real fusion conditions. It is therefore necessary to performexperiments at a multi-kilojoule energy level on medium-scale facilities such asOMEGAor SG-III. An example of two-plasmon decay instabilityexcited in the interaction of two laser beams is considered.展开更多
Reliable simulations of laseretarget interaction on the macroscopic scale are burdened by the fact that the energy transport is very often non-local.This means that the mean-free-path of the transported species is lar...Reliable simulations of laseretarget interaction on the macroscopic scale are burdened by the fact that the energy transport is very often non-local.This means that the mean-free-path of the transported species is larger than the local gradient scale lengths and transport can be no longer considered diffusive.Kinetic simulations are not a feasible option due to tremendous computational demands,limited validity of the collisional operators and inaccurate treatment of thermal radiation.This is the point where hydrodynamic codes with non-local radiation and electron heat transport based on first principles emerge.The simulation code PETE(Plasma Euler and Transport Equations)combines both of them with a laser absorption method based on the Helmholtz equation and a radiation diffusion scheme presented in this article.In the case of modelling ablation processes it can be observed that both,thermal and radiative,transport processes are strongly non-local for laser intensities of 10^(13) W=cm^(2) and above.In this paper simulations for various laser intensities and different ablator materials are presented,where the non-local and diffusive treatments of radiation transport are compared.Significant discrepancies are observed,supporting importance of non-local transport for inertial confinement fusion related studies as well as for pre-pulse generated plasma in ultra-high intensity laseretarget interaction.展开更多
The choice of the correct density profile is crucial in laser wakefield acceleration.In this work,both subsonic and supersonic gas targets are characterized by means of fluid-dynamic simulations and experimental inter...The choice of the correct density profile is crucial in laser wakefield acceleration.In this work,both subsonic and supersonic gas targets are characterized by means of fluid-dynamic simulations and experimental interferometric measurements.The gas targets are studied in different configurations,and the density profiles most suitable for laser wakefield acceleration are discussed.展开更多
基金supported by the Center of Advanced Applied Sciences(CAAS)Project No.(CZ.02.1.01/0.0/0.0/16019/0000778)from the European Regional Development Fundalso supported in part by the Czech Technical University in Prague Project No.SGS22/184/OHK4/3T/14+1 种基金partial funding via EUROfusion Enabling Research Project No.AWP24-ENR-03-CEA-02“Foams as a pathway to energy from high gain direct drive ignition,”within the framework of the EUROfusion Consortium,funded by the European Union via the Euratom Research and Training Program(Grant Agreement No.101052200-EUROfusion)the Czech Ministry of Education,Youth and Sports(CMEYS)for funding the operation of the PALS facility(Grant No.LM2023068)。
文摘The interaction of high-power laser pulses with undercritical foams produced by different techniques but with the same average density is studied at the PALS laser facility.The spatial-temporal evolution of X-ray emission is observed using an X-ray streak camera,electron and ion temperatures are measured by X-ray spectroscopy,and hot-electron production is characterized by monochromatic X-ray imaging.Transmission of a femtosecond laser probe pulse through foams is observed in the near and far fields.In spite of large differences in pore size and foam structure,the velocity of ionization front propagation is quite similar for all the foams studied and is slower than that in a homogeneous material of the same average density.The ion temperature in the plasma behind the ionization front is a few times higher than the electron temperature.Hot-electron production in plastic foams with small pores is strongly suppressed compared with that in solid targets,whereas in foams produced by additive manufacturing,it is significantly increased to the level observed in bare copper foil targets.
基金This project was partially supported by the Advanced Research Using High Intensity Laser Produced Photons and Particles(ADONIS)project(Grant No.CZ.02.1.01/0.0/0.0/16_019/0000789)the CAAS project(Grant No.CZ.02.1.01/0.0/0.0/16_019/0000778)+3 种基金both from the European Regional Development FundThe results of the LQ1606 project were partially obtained with the financial support from the Ministry of Education,Youth and Sports as part of targeted support from the National Programme of Sustainability IIThe authors acknowledge support from the National Natural Science Foundation of China(Grant Nos.11775033,11875241,11975215,11905204,12035002)the Laser Fusion Research Center Funds for Young Talents(Grant No.RCFPD3-2019-6).
文摘The physics of laser-plasma interaction is studied on the Shenguang III prototype laser facility under conditions relevant to inertial confinement fusion designs.A sub-millimeter-size underdense hot plasma is created by ionization of a low-density plastic foam by four high-energy(3.2 kJ)laser beams.An interaction beam is fired with a delay permitting evaluation of the excitation of parametric instabilities at different stages of plasma evolution.Multiple diagnostics are used for plasma characterization,scattered radiation,and accelerated electrons.The experimental results are analyzed with radiation hydrodynamic simulations that take account of foam ionization and homogenization.The measured level of stimulated Raman scattering is almost one order of magnitude larger than that measured in experiments with gasbags and hohlraums on the same installation,possibly because of a greater plasma density.Notable amplification is achieved in high-intensity speckles,indicating the importance of implementing laser temporal smoothing techniques with a large bandwidth for controlling laser propagation and absorption.
基金The authors acknowledge support from the European Regional Development Fund for the following projects:HiFI(No.CZ.02.1.01/0.0/0.0/15_003/0000449),CAAS(No.CZ.02.1.01/0.0/0.0/16_019/0000778),ADONIS(No.CZ.02.1.01/0.0/0.0/16_019/0000789),and ELITAS(No.CZ.02.1.01/0.0/0.0/16_013/0001793)This work has received funding from the European Union Horizon 2020 Research and Innovation Programme under Grant Agreement No.633053(EUROfusion Project No.CfP-AWP17-IFE-CEA-01)+2 种基金Computational resources were provided by the MetaCentrum under the LM2010005 projectIT4InnovationsCentre of Excellence under the CZ.1.05/1.1.00/02.0070 and LM2011033 projectsthe ECLIPSE cluster of ELI-Beamlines.The EPOCH code was developed as part of the UK EPSRC-funded EP/G054940/1 project.
文摘Comprehensive understanding and possible control of parametric instabilities in the context of inertial confinement fusion (ICF) remains achallenging task. The details of the absorption processes and the detrimental effects of hot electrons on the implosion process require as mucheffort on the experimental side as on the theoretical and simulation side. This paper describes a proposal for experimental studies on nonlinearinteraction of intense laser pulses with a high-temperature plasma under conditions corresponding to direct-drive ICF schemes. We propose todevelop a platform for laser-plasma interaction studies based on foam targets. Parametric instabilities are sensitive to the bulk plasma temperatureand the density scale length. Foam targets are sufficiently flexible to allow control of these parameters. However, investigationsconducted on small laser facilities cannot be extrapolated in a reliable way to real fusion conditions. It is therefore necessary to performexperiments at a multi-kilojoule energy level on medium-scale facilities such asOMEGAor SG-III. An example of two-plasmon decay instabilityexcited in the interaction of two laser beams is considered.
文摘Reliable simulations of laseretarget interaction on the macroscopic scale are burdened by the fact that the energy transport is very often non-local.This means that the mean-free-path of the transported species is larger than the local gradient scale lengths and transport can be no longer considered diffusive.Kinetic simulations are not a feasible option due to tremendous computational demands,limited validity of the collisional operators and inaccurate treatment of thermal radiation.This is the point where hydrodynamic codes with non-local radiation and electron heat transport based on first principles emerge.The simulation code PETE(Plasma Euler and Transport Equations)combines both of them with a laser absorption method based on the Helmholtz equation and a radiation diffusion scheme presented in this article.In the case of modelling ablation processes it can be observed that both,thermal and radiative,transport processes are strongly non-local for laser intensities of 10^(13) W=cm^(2) and above.In this paper simulations for various laser intensities and different ablator materials are presented,where the non-local and diffusive treatments of radiation transport are compared.Significant discrepancies are observed,supporting importance of non-local transport for inertial confinement fusion related studies as well as for pre-pulse generated plasma in ultra-high intensity laseretarget interaction.
基金the project Advanced Research Using High Intensity Laser Produced Photons and Particles(CZ.02.1.010.00.0160190000789)from the European Regional Development Fund(ADONIS).
文摘The choice of the correct density profile is crucial in laser wakefield acceleration.In this work,both subsonic and supersonic gas targets are characterized by means of fluid-dynamic simulations and experimental interferometric measurements.The gas targets are studied in different configurations,and the density profiles most suitable for laser wakefield acceleration are discussed.
