Recent experiments at the National Ignition Facility and theoretical modeling suggest that side stimulated Raman scattering(SSRS)instability could reduce laser–plasma coupling and generate considerable fluxes of supr...Recent experiments at the National Ignition Facility and theoretical modeling suggest that side stimulated Raman scattering(SSRS)instability could reduce laser–plasma coupling and generate considerable fluxes of suprathermal hot electrons under interaction conditions envisaged for direct-drive schemes for inertial confinement fusion.Nonetheless,SSRS remains to date one of the least understood parametric instabilities.Here,we report the first angularly and spectrally resolved measurements of scattered light at laser intensities relevant for the shock ignition scheme(I×10^(16)W/cm^(2)),showing significant SSRS growth in the direction perpendicular to the laser polarization.Modification of the focal spot shape and orientation,obtained by using two different random phase plates,and of the density gradient of the plasma,by utilizing exploding foil targets of different thicknesses,clearly reveals a different dependence of backward SRS(BSRS)and SSRS on experimental parameters.While convective BSRS scales with plasma density scale length,as expected by linear theory,the growth of SSRS depends on the spot extension in the direction perpendicular to laser polarization.Our analysis therefore demonstrates that under current experimental conditions,with density scale lengths L_(n)≈60–120μm and spot sizes FWHM≈40–100μm,SSRS is limited by laser beam size rather than by the density scale length of the plasma.展开更多
The coupling of ultra-intense,ultra-short laser pulses with solid targets is heavily dependent on the properties of the vacuum–solid interface and is usually quite low.However,laser absorption can be enhanced via mic...The coupling of ultra-intense,ultra-short laser pulses with solid targets is heavily dependent on the properties of the vacuum–solid interface and is usually quite low.However,laser absorption can be enhanced via micro or nanopatterning of the target surface.Depending on the laser features and target geometry,conditions can be optimized for the generation of hot dense matter,which can be used to produce high-brightness radiation sources or even to accelerate particles to relativistic energies.In this context,ZnO nanowires were grown on metallic,thin-foil targets.The use of a thin-foil substrate was dictated by the need to achieve proton acceleration via target normal sheath acceleration at the rear side.The chemical process parameters were studied in-depth to provide control over the nanowire size,shape,and distribution.Moreover,the manufacturing process was optimized to provide accurate reproducibility of key parameters in the widest possible range and good homogeneity across the entire foil area.展开更多
We report the characterization of the pump absorption and emission dynamic properties of a Tm:Lu2O3 ceramic lasing medium using a three-mirror folded laser cavity.We measured a slope efficiency of 73%,which allowed us...We report the characterization of the pump absorption and emission dynamic properties of a Tm:Lu2O3 ceramic lasing medium using a three-mirror folded laser cavity.We measured a slope efficiency of 73%,which allowed us to retrieve the cross-relaxation coefficient.The behavior of our system was modeled via a set of macroscopic rate equations in both the quasi continuous wave and the pulsed pumping regime.Numerical solutions were obtained,showing a good agreement with the experimental findings.The numerical solution also yielded a cross-relaxation coefficient in very good agreement with the measured one,showing that the cross-relaxation phenomenon approaches the maximum theoretical efficiency.展开更多
Fast electron generation and transport in high-intensity laser–solid interactions induces X-ray emission and drives ion acceleration.Effective production of these sources hinges on an efficient laser absorption into ...Fast electron generation and transport in high-intensity laser–solid interactions induces X-ray emission and drives ion acceleration.Effective production of these sources hinges on an efficient laser absorption into the fast electron population and control of divergence as the beam propagates through the target.Nanowire targets can be employed to increase the laser absorption,but it is not yet clear how the fast electron beam properties are modified.Here we present novel measurements of the emittance of the exiting fast electron beam from irradiated solid planar and nanowire targets via a pepper-pot diagnostic.The measurements indicate a greater fast electron emittance is obtained from nanowire targets.Two-dimensional particle-in-cell simulations support this conclusion,revealing beam defocusing at the wire–substrate boundary,a higher fast electron temperature and transverse oscillatory motion around the wires.展开更多
Implementation of laser-plasma-based acceleration stages in user-oriented facilities requires the definition and deployment of appropriate diagnostic methodologies to monitor and control the acceleration process.An ov...Implementation of laser-plasma-based acceleration stages in user-oriented facilities requires the definition and deployment of appropriate diagnostic methodologies to monitor and control the acceleration process.An overview is given here of optical diagnostics for density measurement in laser-plasma acceleration stages,with emphasis on wellestablished and easily implemented approaches.Diagnostics for both neutral gas and free-electron number density are considered,highlighting real-time measurement capabilities.Optical interferometry,in its various configurations,from standard two-arm to more advanced common-path designs,is discussed,along with spectroscopic techniques such as Stark broadening and Raman scattering.A critical analysis of the diagnostics presented is given concerning their implementation in laser-plasma acceleration stages for the production of high-quality GeV electron bunches.展开更多
We present the main features of the ultrashort, high-intensity laser installation at the Intense Laser Irradiation Laboratory(ILIL) including laser, beam transport and target area specifications. The laboratory was de...We present the main features of the ultrashort, high-intensity laser installation at the Intense Laser Irradiation Laboratory(ILIL) including laser, beam transport and target area specifications. The laboratory was designed to host laser–target interaction experiments of more than 220 TW peak power, in flexible focusing configurations, with ultrarelativistic intensity on the target. Specifications have been established via dedicated optical diagnostic assemblies and commissioning interaction experiments. In this paper we give a summary of laser specifications available to users,including spatial, spectral and temporal contrast features. The layout of the experimental target areas is presented, with attention to the available configurations of laser focusing geometries and diagnostics. Finally, we discuss radiation protection measures and mechanical stability of the laser focal spot on the target.展开更多
基金financial support from the LASERLAB-EUROPE Access to Research Infrastructure Activity (Application No. 23068)carried out within the framework of EUROfusion Enabling Research Projects AWP21-ENR-01-CEA02 and AWP24-ENR-IFE-02-CEA-02+3 种基金received funding from Euratom Research and Training Programme 2021–2025 under Grant No. 633053supported by the Ministry of Youth and Sports of the Czech Republic [Project No. LM2023068 (PALS RI)]by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant Nos. XDA25030200 and XDA25010100)supported by COST (European Cooperation in Science and Technology) through Action CA21128 PROBONO (PROton BOron Nuclear Fusion: from energy production to medical applicatiOns)
文摘Recent experiments at the National Ignition Facility and theoretical modeling suggest that side stimulated Raman scattering(SSRS)instability could reduce laser–plasma coupling and generate considerable fluxes of suprathermal hot electrons under interaction conditions envisaged for direct-drive schemes for inertial confinement fusion.Nonetheless,SSRS remains to date one of the least understood parametric instabilities.Here,we report the first angularly and spectrally resolved measurements of scattered light at laser intensities relevant for the shock ignition scheme(I×10^(16)W/cm^(2)),showing significant SSRS growth in the direction perpendicular to the laser polarization.Modification of the focal spot shape and orientation,obtained by using two different random phase plates,and of the density gradient of the plasma,by utilizing exploding foil targets of different thicknesses,clearly reveals a different dependence of backward SRS(BSRS)and SSRS on experimental parameters.While convective BSRS scales with plasma density scale length,as expected by linear theory,the growth of SSRS depends on the spot extension in the direction perpendicular to laser polarization.Our analysis therefore demonstrates that under current experimental conditions,with density scale lengths L_(n)≈60–120μm and spot sizes FWHM≈40–100μm,SSRS is limited by laser beam size rather than by the density scale length of the plasma.
文摘The coupling of ultra-intense,ultra-short laser pulses with solid targets is heavily dependent on the properties of the vacuum–solid interface and is usually quite low.However,laser absorption can be enhanced via micro or nanopatterning of the target surface.Depending on the laser features and target geometry,conditions can be optimized for the generation of hot dense matter,which can be used to produce high-brightness radiation sources or even to accelerate particles to relativistic energies.In this context,ZnO nanowires were grown on metallic,thin-foil targets.The use of a thin-foil substrate was dictated by the need to achieve proton acceleration via target normal sheath acceleration at the rear side.The chemical process parameters were studied in-depth to provide control over the nanowire size,shape,and distribution.Moreover,the manufacturing process was optimized to provide accurate reproducibility of key parameters in the widest possible range and good homogeneity across the entire foil area.
基金EU Horizon 2020 Research and Innovation Program EuPRAXIA Preparatory Phase,under Grant Agreement No.101079773,EU Horizon IFAST,under Grant Agreement No.101004730This research has been co-funded by the European Union-NextGeneration EU‘Integrated infrastructure initiative in Photonic and Quantum Sciences’-I-PHOQS(IR0000016,ID D2B8D520,CUP B53C22001750006)+1 种基金‘EuPRAXIA Advanced Photon Sources’-EuAPS(IR0000030,CUP I93C21000160006)the Project‘Tuscany Health Ecosystem-THE’‘Spoke 1-Advanced Radiotherapies and Diagnostics in Oncology’funded by the NextGenerationEU(PNRR),Codice progetto ECS00000017,D.D.MUR No.105523 May 2022.
文摘We report the characterization of the pump absorption and emission dynamic properties of a Tm:Lu2O3 ceramic lasing medium using a three-mirror folded laser cavity.We measured a slope efficiency of 73%,which allowed us to retrieve the cross-relaxation coefficient.The behavior of our system was modeled via a set of macroscopic rate equations in both the quasi continuous wave and the pulsed pumping regime.Numerical solutions were obtained,showing a good agreement with the experimental findings.The numerical solution also yielded a cross-relaxation coefficient in very good agreement with the measured one,showing that the cross-relaxation phenomenon approaches the maximum theoretical efficiency.
基金the NextGenerationEU(PNRR)Integrated Infrastructure Initiative in Photonic and Quantum Sciences(IPHOQS)(CUP B53C22001750006,ID D2B8D520,IR0000016)EuPRAXIA Advanced Photon Sources(EuAPS)(CUP I93C21000160006,IR0000030)+3 种基金funding from the Engineering and Physical Sciences Research Council(EP/L01663X/1)the Royal Society International Exchange(IES/R3/170248)Computing resources were provided by STFC Scientific Computing Department’s SCARF clusterfunded by the UK EPSRC(grants EP/G054950/1,EP/G056803/1,EP/G055165/1 and EP/M022463/1).
文摘Fast electron generation and transport in high-intensity laser–solid interactions induces X-ray emission and drives ion acceleration.Effective production of these sources hinges on an efficient laser absorption into the fast electron population and control of divergence as the beam propagates through the target.Nanowire targets can be employed to increase the laser absorption,but it is not yet clear how the fast electron beam properties are modified.Here we present novel measurements of the emittance of the exiting fast electron beam from irradiated solid planar and nanowire targets via a pepper-pot diagnostic.The measurements indicate a greater fast electron emittance is obtained from nanowire targets.Two-dimensional particle-in-cell simulations support this conclusion,revealing beam defocusing at the wire–substrate boundary,a higher fast electron temperature and transverse oscillatory motion around the wires.
基金support from the European Unions Horizon 2020 research and innovation program under Grant Agreement No.653782-EuPRAXIAthe MIUR-funded Italian research Network ELI-Italy
文摘Implementation of laser-plasma-based acceleration stages in user-oriented facilities requires the definition and deployment of appropriate diagnostic methodologies to monitor and control the acceleration process.An overview is given here of optical diagnostics for density measurement in laser-plasma acceleration stages,with emphasis on wellestablished and easily implemented approaches.Diagnostics for both neutral gas and free-electron number density are considered,highlighting real-time measurement capabilities.Optical interferometry,in its various configurations,from standard two-arm to more advanced common-path designs,is discussed,along with spectroscopic techniques such as Stark broadening and Raman scattering.A critical analysis of the diagnostics presented is given concerning their implementation in laser-plasma acceleration stages for the production of high-quality GeV electron bunches.
基金The ILIL-PW upgrade was established in the framework of the Italian Research Network on Extreme Light Infrastructure(ELI-Italy)funded by CNRfinancial contribution from the Eu PRAXIA project of the EU Horizon 2020 Research and Innovation Program under Grant Agreement No.653782the Line for Laser Light Ion Acceleration(L3IA)project funded by INFN,Italy。
文摘We present the main features of the ultrashort, high-intensity laser installation at the Intense Laser Irradiation Laboratory(ILIL) including laser, beam transport and target area specifications. The laboratory was designed to host laser–target interaction experiments of more than 220 TW peak power, in flexible focusing configurations, with ultrarelativistic intensity on the target. Specifications have been established via dedicated optical diagnostic assemblies and commissioning interaction experiments. In this paper we give a summary of laser specifications available to users,including spatial, spectral and temporal contrast features. The layout of the experimental target areas is presented, with attention to the available configurations of laser focusing geometries and diagnostics. Finally, we discuss radiation protection measures and mechanical stability of the laser focal spot on the target.
