This paper provides an overview of the current status of ultrafast and ultra-intense lasers with peak powers exceeding100 TW and examines the research activities in high-energy-density physics within China.Currently,1...This paper provides an overview of the current status of ultrafast and ultra-intense lasers with peak powers exceeding100 TW and examines the research activities in high-energy-density physics within China.Currently,10 high-intensity lasers with powers over 100 TW are operational,and about 10 additional lasers are being constructed at various institutes and universities.These facilities operate either independently or are combined with one another,thereby offering substantial support for both Chinese and international research and development efforts in high-energy-density physics.展开更多
When this article was originally published in High Power Laser Science and Engineering it contained an error in the name of the author Jiandong Liu.This has now been fixed.The publisher apologises for this error.
Laser-driven inertial confinement fusion(ICF)diagnostics play a crucial role in understanding the complex physical processes governing ICF and enabling ignition.During the ICF process,the interaction between the high-...Laser-driven inertial confinement fusion(ICF)diagnostics play a crucial role in understanding the complex physical processes governing ICF and enabling ignition.During the ICF process,the interaction between the high-power laser and ablation material leads to the formation of a plasma critical surface,which reflects a significant portion of the driving laser,reducing the efficiency of laser energy conversion into implosive kinetic energy.Effective diagnostic methods for the critical surface remain elusive.In this work,we propose a novel optical diagnostic approach to investigate the plasma critical surface.This method has been experimentally validated,providing new insights into the critical surface morphology and dynamics.This advancement represents a significant step forward in ICF diagnostic capabilities,with the potential to inform strategies for enhancing the uniformity of the driving laser and target surface,ultimately improving the efficiency of converting laser energy into implosion kinetic energy and enabling ignition.展开更多
Machine learning has already shown promising potential in tiled-aperture coherent beam combining(CBC)to achieve versatile advanced applications.By sampling the spatially separated laser array before the combiner and d...Machine learning has already shown promising potential in tiled-aperture coherent beam combining(CBC)to achieve versatile advanced applications.By sampling the spatially separated laser array before the combiner and detuning the optical path delays,deep learning techniques are incorporated into filled-aperture CBC to achieve single-step phase control.The neural network is trained with far-field diffractive patterns at the defocus plane to establish one-to-one phase-intensity mapping,and the phase prediction accuracy is significantly enhanced thanks to the strategies of sin-cos loss function and two-layer output of the phase vector that are adopted to resolve the phase discontinuity issue.The results indicate that the trained network can predict phases with improved accuracy,and phase-locking of nine-channel filled-aperture CBC has been numerically demonstrated in a single step with a residual phase ofλ/70.To the best of our knowledge,this is the first time that machine learning has been made feasible in filled-aperture CBC laser systems.展开更多
We present coherent beam combining of nanosecond pulses with 20-J energy and large beams using a Sagnac interferometer geometry based on Nd:glass rod-type amplifiers.In this study,we demonstrate that coherent beam com...We present coherent beam combining of nanosecond pulses with 20-J energy and large beams using a Sagnac interferometer geometry based on Nd:glass rod-type amplifiers.In this study,we demonstrate that coherent beam combining is compatible with large-diameter energetic beams,presenting,therefore,an interesting and solid perspective towards the performance improvement of large-scale laser facilities,especially in terms of high-repetition-rate and highenergy operation.We demonstrate that for energy of 20 J,the coherent combination efficiency is around 92%,with high beam quality and long-term stability.A thorough temporal and spatial characterization of the system's operation is provided to forecast the various potentialities available for large-scale facilities.展开更多
Spatial intensity modulation in amplified laser beams,particularly hot spots,critically constrains attainable pulse peak power due to the damage threshold limitations of four-grating compressors.This study demonstrate...Spatial intensity modulation in amplified laser beams,particularly hot spots,critically constrains attainable pulse peak power due to the damage threshold limitations of four-grating compressors.This study demonstrates that the double-smoothing grating compressor(DSGC)configuration effectively suppresses modulation through directional beam smoothing.Our systematic investigation validated the double-smoothing effect through numerical simulations and experimental measurements,with comprehensive spatiotemporal analysis revealing excellent agreement between numerical and practical pulse characteristics.Crucially,the DSGC enables a 1.74 times energy output boost compared to conventional compressors.These findings establish the DSGC as a pivotal advancement for next-generation ultrahighpower laser systems,providing a viable pathway toward hundreds of PW output through optimized spatial energy redistribution.展开更多
The betatron radiation source features a micrometer-scale source size,a femtosecond-scale pulse duration,milliradianlevel divergence angles and a broad spectrum exceeding tens of keV.It is conducive to the high-contra...The betatron radiation source features a micrometer-scale source size,a femtosecond-scale pulse duration,milliradianlevel divergence angles and a broad spectrum exceeding tens of keV.It is conducive to the high-contrast imaging of minute structures and for investigating interdisciplinary ultrafast processes.In this study,we present a betatron X-ray source derived from a high-charge,high-energy electron beam through a laser wakefield accelerator driven by the 1 PW/0.1 Hz laser system at the Shanghai Superintense Ultrafast Laser Facility(SULF).The critical energy of the betatron X-ray source is 22±5 keV.The maximum X-ray flux reaches up to 4×10^(9)photons for each shot in the spectral range of 5-30 keV.Correspondingly,the experiment demonstrates a peak brightness of 1.0×10^(23)photons·s^(-1)·mm^(-2)·mrad^(-2)·0.1%BW^(-1),comparable to those demonstrated by third-generation synchrotron light sources.In addition,the imaging capability of the betatron X-ray source is validated.This study lays the foundation for future imaging applications.展开更多
Low-density polymer foams pre-ionized by a well-controlled nanosecond pulse are excellent plasma targets to trigger direct laser acceleration(DLA)of electrons by sub-picosecond relativistic laser pulses.In this work,t...Low-density polymer foams pre-ionized by a well-controlled nanosecond pulse are excellent plasma targets to trigger direct laser acceleration(DLA)of electrons by sub-picosecond relativistic laser pulses.In this work,the influence of the nanosecond pulse on the DLA process is investigated.The density profile of plasma generated after irradiating foam with a nanosecond pulse was simulated with a two-dimensional hydrodynamic code,which takes into account the high aspect ratio of interaction and the microstructure of polymer foams.The obtained plasma density profile was used as input to the three-dimensional particle-in-cell code to simulate energy,angular distributions and charge carried by the directional fraction of DLA electrons.The modelling shows good agreement with the experiment and in general a weak dependence of the electron spectra on the plasma profiles,which contain a density up-ramp and a region of near-critical electron density.This explains the high DLA stability in pre-ionized foams,which is important for applications.展开更多
We present a novel scheme for rapid quantitative analysis of debris generated during experiments with solid targets following relativistic laser–plasma interaction at high-power laser facilities.Results are supported...We present a novel scheme for rapid quantitative analysis of debris generated during experiments with solid targets following relativistic laser–plasma interaction at high-power laser facilities.Results are supported by standard analysis techniques.Experimental data indicate that predictions by available modelling for non-mass-limited targets are reasonable,with debris of the order of hundreds ofμg per shot.We detect for the first time two clearly distinct types of debris emitted from the same interaction.A fraction of the debris is ejected directionally,following the target normal(rear and interaction side).The directional debris ejection towards the interaction side is larger than on the side of the target rear.The second type of debris is characterized by a more spherically uniform ejection,albeit with a small asymmetry that favours ejection towards the target rear side.展开更多
We demonstrated a high-power,high-energy regenerative amplifier(RA)based on Yb-doped CaGdAlO_(4)(Yb:CALGO)crystal,which achieves a maximum average power exceeding 50 W at a repetition rate greater than 50 kHz,and a ma...We demonstrated a high-power,high-energy regenerative amplifier(RA)based on Yb-doped CaGdAlO_(4)(Yb:CALGO)crystal,which achieves a maximum average power exceeding 50 W at a repetition rate greater than 50 kHz,and a maximum pulse energy of approximately 7 mJ at a repetition rate of up to 5 kHz.After compression,130 fs pulses with a peak power of nearly 45 GW are achieved.To the best of our knowledge,this represents the highest average power and pulse energy reported for a Yb:CALGO RA.The RA cavity is specifically designed to maintain excellent stability and output beam quality under a pumping power of 380 W,resulting in a continuous-wave output power exceeding 70 W.For the seeder,a fiber laser utilizing a nonlinear amplification process,which yields a broadband spectrum to support approximately 80 fs pulses,is employed for the high-peak-power pulse generation.展开更多
Polarization smoothing can effectively improve the uniformity of focal spots.In this study,we theoretically and experimentally investigated the polarization synthesis of the focal spot under a birefringent wedge(BW)an...Polarization smoothing can effectively improve the uniformity of focal spots.In this study,we theoretically and experimentally investigated the polarization synthesis of the focal spot under a birefringent wedge(BW)and speckle under the coupling of the BW and continuous phase plate.Polarization distribution was experimentally obtained using rotating quarter-wave plate measurement under a specific wedge angle.The simulated and experimental results are consistent,demonstrating that the focal spot is in a state of coexistence of elliptical and linear polarizations.In addition,the polarization state is determined by the ratio of the amplitudes and the phase difference between the sub-beams.The simulation results showed that the proportion of linear polarization increased with the separation angle of the sub-beam.In contrast,it decreased with the incident light aperture.This research is crucial for accurately describing the polarization distribution and further understanding the laser–plasma interactions.展开更多
High-energy,short-pulse laser-driven proton–boron(p–11B)fusion has attracted growing interest due to its aneutronic character and potential for clean energy generation.In this study,we report on two experimental cam...High-energy,short-pulse laser-driven proton–boron(p–11B)fusion has attracted growing interest due to its aneutronic character and potential for clean energy generation.In this study,we report on two experimental campaigns carried out at the LFEX laser facility using petawatt-class laser systems(energy~1.2–1.4 kJ,pulse duration 2.7 ps,peak intensity~(2–3)×10^(19)W/cm^(2)).The experiments explored the influence of complex target geometries–including spherical,cylindrical and wedge-shaped configurations–onα-particle yield.Our results demonstrate that spherical targets can enhanceα-particle production by up to two orders of magnitude compared to planar targets of identical composition and also lead to a noticeable shift of theα-particle energy spectrum toward higher values.Furthermore,we implemented a novel diagnostic technique for unambiguousα-particle detection using a CR-39 detector integrated into a Thomson parabola spectrometer.Particle-in-cell simulations performed with the Smilei code provide additional insight into the role of self-generated magnetic fields in modulating particle dynamics.These simulations highlight the critical interplay among target geometry,confinement effects and fusion efficiency.Overall,our findings underscore the potential of optimized target designs to significantly enhance fusion yield andα-particle output in p–11B fusion,with promising implications for the development of laser-drivenα-particle sources and advanced clean energy concepts.展开更多
High-power lasers are vital for particle acceleration,imaging,fusion and materials processing,requiring precise control and high-energy delivery.Laser plasma accelerators(LPAs)demand laser positional stability at focu...High-power lasers are vital for particle acceleration,imaging,fusion and materials processing,requiring precise control and high-energy delivery.Laser plasma accelerators(LPAs)demand laser positional stability at focus to ensure consistent electron beams in applications such as X-ray free-electron lasers and high-energy colliders.Achieving this stability is especially challenging for the low-repetition-rate lasers in current LPAs.We present a machine learning method that predicts and corrects laser pointing instabilities in real-time using a high-frequency pilot beam.By preemptively adjusting a correction mirror,this approach overcomes traditional feedback limits.Demonstrated on the BELLA petawatt laser operating at the terawatt level(30 mJ amplification),our method achieved root mean square pointing stabilization of 0.34 and 0.59μrad in the x and y directions,reducing jitter by 65%and 47%,respectively.This is the first successful application of predictive control for shot-to-shot stabilization in low-repetition-rate laser systems,paving the way for full-energy petawatt lasers and transformative advances across science,industry and security.展开更多
Accurate characterization of high-power laser parameters,especially the near-field and far-field distributions,is crucial for inertial confinement fusion experiments.In this paper,we propose a method for computational...Accurate characterization of high-power laser parameters,especially the near-field and far-field distributions,is crucial for inertial confinement fusion experiments.In this paper,we propose a method for computationally reconstructing the complex amplitude of high-power laser beams using modified coherent modulation imaging.This method has the advantage of being able to simultaneously calculate both the near-field(intensity and wavefront/phase)and far-field(focal-spot)distributions using the reconstructed complex amplitude.More importantly,the focal-spot distributions at different focal planes can also be calculated.To verify the feasibility,the complex amplitude optical field of the highpower pulsed laser was measured after static aberrations calibration.Experimental results also indicate that the near-field wavefront resolution of this method is higher than that of the Hartmann measurement.In addition,the far-field focal spot exhibits a higher dynamic range(176 dB)than that of traditional direct imaging(62 dB).展开更多
High gain greater than 106 is crucial for the preamplifiers of joule-class high-energy lasers.In this work,we present a specially designed compact amplifier using 0.5%Nd,5%Gd:SrF_(2)and 0.5%Nd,5%Y:SrF_(2)crystals.The ...High gain greater than 106 is crucial for the preamplifiers of joule-class high-energy lasers.In this work,we present a specially designed compact amplifier using 0.5%Nd,5%Gd:SrF_(2)and 0.5%Nd,5%Y:SrF_(2)crystals.The irregular crystal shape enhances the gain length of the laser beam and helps suppress parasitic oscillations.The amplified spontaneous emission(ASE)induced by the high gain is analyzed through ray tracing.The balance between gain and ASE is estimated via numerical simulation.The gain spectral characteristics of the two-stage two-pass amplifier are examined,demonstrating the advantages of using different crystals,with bandwidths up to 8 nm and gains over 106.In addition,the temperature and stress distributions in the Nd,Gd:SrF_(2)crystal are simulated.This work is expected to contribute to the development of high-peak-power(≥terawatt-class)high-energy(joule-class)laser devices.展开更多
Ultraintense laser–plasma experiments generate a variety of high-energy radiations,including nonlinear inverse Compton scattered(NCS)X-rays,which are expected to be a key experimental observable as we transition into...Ultraintense laser–plasma experiments generate a variety of high-energy radiations,including nonlinear inverse Compton scattered(NCS)X-rays,which are expected to be a key experimental observable as we transition into the quantum electrodynamic plasma regime.However,there is also a high bremsstrahlung X-ray background that reduces our ability to observe NCS X-rays.Previous numerical studies comparing NCS and bremsstrahlung emissions fail to capture the full temporal emission of both processes.We present for the first time two-dimensional particle-in-cell(PIC)and three-dimensional hybrid-PIC EPOCH simulations that capture up to 150 ps of the laser–plasma interaction and directly compare the NCS and bremsstrahlung emissions for a plastic target for intensities of 10^(20)-10^(23)W/cm^(2).We present angular distribution plots where the NCS emission is seen to dominate at intensities greater than 5×10^(21)W/cm^(2)and the target design is seen to successfully divert the bremsstrahlung signal away from the NCS lobe regions,making the experimental observation of nonlinear inverse Compton scattering at lower intensities more likely.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
Based on a 4f system,a 0?reflector and a single laser diode side-pump amplifier,a new amplifier is designed to compensate the spherical aberration of the amplified laser generated by a single laser diode side-pump amp...Based on a 4f system,a 0?reflector and a single laser diode side-pump amplifier,a new amplifier is designed to compensate the spherical aberration of the amplified laser generated by a single laser diode side-pump amplifier and enhance the power of the amplified laser.Furthermore,the role of the 4f system in the passive spherical aberration compensation and its effect on the amplified laser are discussed in detail.The results indicate that the amplification efficiency is enhanced by incorporating a 4f system in a double-pass amplifier and placing a 0?reflector only at the focal point of the single-pass amplified laser.This method also effectively uses the heat from the gain medium(neodymiumdoped yttrium aluminium garnet)of the amplifier to compensate the spherical aberration of the amplified laser.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
Measurements of the bunch arrival times at the European X-ray free-electron laser show noise contributions in the spectral range between 0.05 and 0.5 Hz with peak-to-peak jitter of up to 25 fs.Correlation with distrib...Measurements of the bunch arrival times at the European X-ray free-electron laser show noise contributions in the spectral range between 0.05 and 0.5 Hz with peak-to-peak jitter of up to 25 fs.Correlation with distributed acoustic sensing measurements confirms the seismic origin.The seismic noise in this frequency band is known to be oceangenerated microseism.Both primary and secondary ocean-generated microseisms were identified using seismometers and a numerical ocean wave model.Whereas secondary microseism has a strong impact on the bunch arrival time,primary microseism has no notable effect.Rayleigh waves cause the effect,while Love waves have minimal impact.In the presented cases,the noise originates from the North Atlantic and/or the North Sea.The amplitude of the noise depends on the local weather conditions and is much stronger in winter.Ocean-generated microseism is a significant bottleneck that must be addressed to achieve femtosecond bunch arrival time stability in the sub-Hz regime.展开更多
文摘This paper provides an overview of the current status of ultrafast and ultra-intense lasers with peak powers exceeding100 TW and examines the research activities in high-energy-density physics within China.Currently,10 high-intensity lasers with powers over 100 TW are operational,and about 10 additional lasers are being constructed at various institutes and universities.These facilities operate either independently or are combined with one another,thereby offering substantial support for both Chinese and international research and development efforts in high-energy-density physics.
文摘When this article was originally published in High Power Laser Science and Engineering it contained an error in the name of the author Jiandong Liu.This has now been fixed.The publisher apologises for this error.
基金supported by the National Natural Science Foundation of China(NSFC)(12074399,12204500 and 12004403)the Key Projects of Intergovernmental International Scientific and Technological Innovation Cooperation(2021YFE0116700)+1 种基金the Shanghai Natural Science Foundation(20ZR1464400)the Shanghai Sailing Program(22YF1455300).
文摘Laser-driven inertial confinement fusion(ICF)diagnostics play a crucial role in understanding the complex physical processes governing ICF and enabling ignition.During the ICF process,the interaction between the high-power laser and ablation material leads to the formation of a plasma critical surface,which reflects a significant portion of the driving laser,reducing the efficiency of laser energy conversion into implosive kinetic energy.Effective diagnostic methods for the critical surface remain elusive.In this work,we propose a novel optical diagnostic approach to investigate the plasma critical surface.This method has been experimentally validated,providing new insights into the critical surface morphology and dynamics.This advancement represents a significant step forward in ICF diagnostic capabilities,with the potential to inform strategies for enhancing the uniformity of the driving laser and target surface,ultimately improving the efficiency of converting laser energy into implosion kinetic energy and enabling ignition.
文摘Machine learning has already shown promising potential in tiled-aperture coherent beam combining(CBC)to achieve versatile advanced applications.By sampling the spatially separated laser array before the combiner and detuning the optical path delays,deep learning techniques are incorporated into filled-aperture CBC to achieve single-step phase control.The neural network is trained with far-field diffractive patterns at the defocus plane to establish one-to-one phase-intensity mapping,and the phase prediction accuracy is significantly enhanced thanks to the strategies of sin-cos loss function and two-layer output of the phase vector that are adopted to resolve the phase discontinuity issue.The results indicate that the trained network can predict phases with improved accuracy,and phase-locking of nine-channel filled-aperture CBC has been numerically demonstrated in a single step with a residual phase ofλ/70.To the best of our knowledge,this is the first time that machine learning has been made feasible in filled-aperture CBC laser systems.
基金funding from the European Union’s HORIZON-INFRA-2022-TECH-01 call under grant agreement number 101095207funded by the‘SESAME filières PIA’call for projects from Bpifrance for the‘CRONOS’project,contract numbers DOS0153845/00 and DOS0153842/00。
文摘We present coherent beam combining of nanosecond pulses with 20-J energy and large beams using a Sagnac interferometer geometry based on Nd:glass rod-type amplifiers.In this study,we demonstrate that coherent beam combining is compatible with large-diameter energetic beams,presenting,therefore,an interesting and solid perspective towards the performance improvement of large-scale laser facilities,especially in terms of high-repetition-rate and highenergy operation.We demonstrate that for energy of 20 J,the coherent combination efficiency is around 92%,with high beam quality and long-term stability.A thorough temporal and spatial characterization of the system's operation is provided to forecast the various potentialities available for large-scale facilities.
基金supported by the Shanghai Municipal Natural Science Foundation(Grant No.20ZR1464500)the National Natural Science Foundation of China(NSFC)(Grant Nos.61905257 and U1930115)+1 种基金the Shanghai Municipal Science and Technology Major Project(Grant No.2017SHZDZX02)the Ministry of Science and Higher Education of the Russian Federation(Project No.FFUF-2024-0038)。
文摘Spatial intensity modulation in amplified laser beams,particularly hot spots,critically constrains attainable pulse peak power due to the damage threshold limitations of four-grating compressors.This study demonstrates that the double-smoothing grating compressor(DSGC)configuration effectively suppresses modulation through directional beam smoothing.Our systematic investigation validated the double-smoothing effect through numerical simulations and experimental measurements,with comprehensive spatiotemporal analysis revealing excellent agreement between numerical and practical pulse characteristics.Crucially,the DSGC enables a 1.74 times energy output boost compared to conventional compressors.These findings establish the DSGC as a pivotal advancement for next-generation ultrahighpower laser systems,providing a viable pathway toward hundreds of PW output through optimized spatial energy redistribution.
基金supported by the National Natural Science Foundation of China(Grant Nos.12388102,12225411,12105353 and 12174410)the CAS Project for Young Scientists in Basic Research(Grant No.YSBR060)+3 种基金the Program of Shanghai Academic Research Leader(Grant No.22XD1424200)the State Key Laboratory Program of the Chinese Ministry of Science and Technologythe CAS Youth Innovation Promotion Association(Grant No.2022242)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDB0890201 and XDB0890202)。
文摘The betatron radiation source features a micrometer-scale source size,a femtosecond-scale pulse duration,milliradianlevel divergence angles and a broad spectrum exceeding tens of keV.It is conducive to the high-contrast imaging of minute structures and for investigating interdisciplinary ultrafast processes.In this study,we present a betatron X-ray source derived from a high-charge,high-energy electron beam through a laser wakefield accelerator driven by the 1 PW/0.1 Hz laser system at the Shanghai Superintense Ultrafast Laser Facility(SULF).The critical energy of the betatron X-ray source is 22±5 keV.The maximum X-ray flux reaches up to 4×10^(9)photons for each shot in the spectral range of 5-30 keV.Correspondingly,the experiment demonstrates a peak brightness of 1.0×10^(23)photons·s^(-1)·mm^(-2)·mrad^(-2)·0.1%BW^(-1),comparable to those demonstrated by third-generation synchrotron light sources.In addition,the imaging capability of the betatron X-ray source is validated.This study lays the foundation for future imaging applications.
基金funded by the German Ministry for Education and Research(BMBF)under contract No.05P21SJFA2the Ministry of Science and Higher Education of the Russian Federation(Agreement No.075-15-2021-1361)+1 种基金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Low-density polymer foams pre-ionized by a well-controlled nanosecond pulse are excellent plasma targets to trigger direct laser acceleration(DLA)of electrons by sub-picosecond relativistic laser pulses.In this work,the influence of the nanosecond pulse on the DLA process is investigated.The density profile of plasma generated after irradiating foam with a nanosecond pulse was simulated with a two-dimensional hydrodynamic code,which takes into account the high aspect ratio of interaction and the microstructure of polymer foams.The obtained plasma density profile was used as input to the three-dimensional particle-in-cell code to simulate energy,angular distributions and charge carried by the directional fraction of DLA electrons.The modelling shows good agreement with the experiment and in general a weak dependence of the electron spectra on the plasma profiles,which contain a density up-ramp and a region of near-critical electron density.This explains the high DLA stability in pre-ionized foams,which is important for applications.
基金funding from the European Union’s Horizon 2020 research and innovation programme through the European IMPULSE project under grant agreement No.871161 and LASERLAB-EUROPE V under grant agreement No.871124from grant PDC2021-120933-I00 funded by MCIN/AEI/10.13039/501100011033 and by the European Union Next Generation EU/PRTR+4 种基金from grant PID2021-125389OA-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER,UE and by‘ERDF A way of making Europe’by the European Union and in addition to Unidad de Investigacion Consolidada de la Junta de Castilla y Leon No.CLP087U16The UPM47 campaign was funded through IOSIN,Nucleu PN-IFIN-HH 23-26 Code PN 2321the ELI-NP Phase II,a project co-financed by the Romanian Government and the European Union through the European Regional Development Fund and the Competitiveness Operational Programme(1/07.07.2016,COP,ID 1334)This research was funded,in part,by the French Agence Nationale de la Recherche(ANR),Project No.ANR-22-CE30-0044supported by the Ministry of Youth and Sports of the Czech Republic(Project Nos.LM2023068 and LM2018114(PALS RI)).
文摘We present a novel scheme for rapid quantitative analysis of debris generated during experiments with solid targets following relativistic laser–plasma interaction at high-power laser facilities.Results are supported by standard analysis techniques.Experimental data indicate that predictions by available modelling for non-mass-limited targets are reasonable,with debris of the order of hundreds ofμg per shot.We detect for the first time two clearly distinct types of debris emitted from the same interaction.A fraction of the debris is ejected directionally,following the target normal(rear and interaction side).The directional debris ejection towards the interaction side is larger than on the side of the target rear.The second type of debris is characterized by a more spherically uniform ejection,albeit with a small asymmetry that favours ejection towards the target rear side.
基金supported by the National Key R&D Program of China(2022YFF0706001)the Innovation Program for Quantum Science and Technology(2023ZD0301000)+1 种基金the National Natural Science Foundation of China(62205206,62375173)the China Postdoctoral Science Foundation(2023M732320).
文摘We demonstrated a high-power,high-energy regenerative amplifier(RA)based on Yb-doped CaGdAlO_(4)(Yb:CALGO)crystal,which achieves a maximum average power exceeding 50 W at a repetition rate greater than 50 kHz,and a maximum pulse energy of approximately 7 mJ at a repetition rate of up to 5 kHz.After compression,130 fs pulses with a peak power of nearly 45 GW are achieved.To the best of our knowledge,this represents the highest average power and pulse energy reported for a Yb:CALGO RA.The RA cavity is specifically designed to maintain excellent stability and output beam quality under a pumping power of 380 W,resulting in a continuous-wave output power exceeding 70 W.For the seeder,a fiber laser utilizing a nonlinear amplification process,which yields a broadband spectrum to support approximately 80 fs pulses,is employed for the high-peak-power pulse generation.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA25020304)the SG-II laser facility.
文摘Polarization smoothing can effectively improve the uniformity of focal spots.In this study,we theoretically and experimentally investigated the polarization synthesis of the focal spot under a birefringent wedge(BW)and speckle under the coupling of the BW and continuous phase plate.Polarization distribution was experimentally obtained using rotating quarter-wave plate measurement under a specific wedge angle.The simulated and experimental results are consistent,demonstrating that the focal spot is in a state of coexistence of elliptical and linear polarizations.In addition,the polarization state is determined by the ratio of the amplitudes and the phase difference between the sub-beams.The simulation results showed that the proportion of linear polarization increased with the separation angle of the sub-beam.In contrast,it decreased with the incident light aperture.This research is crucial for accurately describing the polarization distribution and further understanding the laser–plasma interactions.
基金the framework of the EUROfusion Consortium,funded by the European Union via the Euratom Research and Training Programme(Grant Agreement No.101052200–EUROfusion)Co-authors from Deakin University gratefully thank the Australian Research Council for financial support under the Linkage[LP200301537]+2 种基金supported by COST(European Cooperation in Science and Technology)through Action CA21128 PROBONO(PROton BOron Nuclear Fusion:from energy production to medical applicati Ons)the support of the Czech Science Foundation through Grant No.GACR24-11398Sthe support of HB11 Energy Holdings Pty,Australia,through its collaborative science program。
文摘High-energy,short-pulse laser-driven proton–boron(p–11B)fusion has attracted growing interest due to its aneutronic character and potential for clean energy generation.In this study,we report on two experimental campaigns carried out at the LFEX laser facility using petawatt-class laser systems(energy~1.2–1.4 kJ,pulse duration 2.7 ps,peak intensity~(2–3)×10^(19)W/cm^(2)).The experiments explored the influence of complex target geometries–including spherical,cylindrical and wedge-shaped configurations–onα-particle yield.Our results demonstrate that spherical targets can enhanceα-particle production by up to two orders of magnitude compared to planar targets of identical composition and also lead to a noticeable shift of theα-particle energy spectrum toward higher values.Furthermore,we implemented a novel diagnostic technique for unambiguousα-particle detection using a CR-39 detector integrated into a Thomson parabola spectrometer.Particle-in-cell simulations performed with the Smilei code provide additional insight into the role of self-generated magnetic fields in modulating particle dynamics.These simulations highlight the critical interplay among target geometry,confinement effects and fusion efficiency.Overall,our findings underscore the potential of optimized target designs to significantly enhance fusion yield andα-particle output in p–11B fusion,with promising implications for the development of laser-drivenα-particle sources and advanced clean energy concepts.
基金supported by the Office of Science,Office of High Energy Physics,of the US Department of Energythe Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory under contract No.DE-AC02-05CH11231。
文摘High-power lasers are vital for particle acceleration,imaging,fusion and materials processing,requiring precise control and high-energy delivery.Laser plasma accelerators(LPAs)demand laser positional stability at focus to ensure consistent electron beams in applications such as X-ray free-electron lasers and high-energy colliders.Achieving this stability is especially challenging for the low-repetition-rate lasers in current LPAs.We present a machine learning method that predicts and corrects laser pointing instabilities in real-time using a high-frequency pilot beam.By preemptively adjusting a correction mirror,this approach overcomes traditional feedback limits.Demonstrated on the BELLA petawatt laser operating at the terawatt level(30 mJ amplification),our method achieved root mean square pointing stabilization of 0.34 and 0.59μrad in the x and y directions,reducing jitter by 65%and 47%,respectively.This is the first successful application of predictive control for shot-to-shot stabilization in low-repetition-rate laser systems,paving the way for full-energy petawatt lasers and transformative advances across science,industry and security.
基金supported by the Project of the Ministry of Industry and Information Technology(Grant No.TC220H05L)the National Natural Science Foundation of China(NSFC)(Grant Nos.61905261,61827816 and 11875308)+1 种基金the Shanghai Sailing Program(Grant No.18YF1426600)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA25020306).
文摘Accurate characterization of high-power laser parameters,especially the near-field and far-field distributions,is crucial for inertial confinement fusion experiments.In this paper,we propose a method for computationally reconstructing the complex amplitude of high-power laser beams using modified coherent modulation imaging.This method has the advantage of being able to simultaneously calculate both the near-field(intensity and wavefront/phase)and far-field(focal-spot)distributions using the reconstructed complex amplitude.More importantly,the focal-spot distributions at different focal planes can also be calculated.To verify the feasibility,the complex amplitude optical field of the highpower pulsed laser was measured after static aberrations calibration.Experimental results also indicate that the near-field wavefront resolution of this method is higher than that of the Hartmann measurement.In addition,the far-field focal spot exhibits a higher dynamic range(176 dB)than that of traditional direct imaging(62 dB).
基金supported by the National Major Project of China (Grant No.GFZX020503.10)the National Natural Science Foundation of China (Grant Nos.12074353,62405298 and 61925508)the CAS Project for Young Scientists in Basic Research (Grant No.YSBR-024)
文摘High gain greater than 106 is crucial for the preamplifiers of joule-class high-energy lasers.In this work,we present a specially designed compact amplifier using 0.5%Nd,5%Gd:SrF_(2)and 0.5%Nd,5%Y:SrF_(2)crystals.The irregular crystal shape enhances the gain length of the laser beam and helps suppress parasitic oscillations.The amplified spontaneous emission(ASE)induced by the high gain is analyzed through ray tracing.The balance between gain and ASE is estimated via numerical simulation.The gain spectral characteristics of the two-stage two-pass amplifier are examined,demonstrating the advantages of using different crystals,with bandwidths up to 8 nm and gains over 106.In addition,the temperature and stress distributions in the Nd,Gd:SrF_(2)crystal are simulated.This work is expected to contribute to the development of high-peak-power(≥terawatt-class)high-energy(joule-class)laser devices.
基金the Science and Technology Facilities Council and the Engineering and Physical Sciences Research Council for their funding towards this project,and the continued support of research into QED laser–plasma physicsfunding fromthe Engineering and Physical Sciences Research Council[EP/S022430/1]。
文摘Ultraintense laser–plasma experiments generate a variety of high-energy radiations,including nonlinear inverse Compton scattered(NCS)X-rays,which are expected to be a key experimental observable as we transition into the quantum electrodynamic plasma regime.However,there is also a high bremsstrahlung X-ray background that reduces our ability to observe NCS X-rays.Previous numerical studies comparing NCS and bremsstrahlung emissions fail to capture the full temporal emission of both processes.We present for the first time two-dimensional particle-in-cell(PIC)and three-dimensional hybrid-PIC EPOCH simulations that capture up to 150 ps of the laser–plasma interaction and directly compare the NCS and bremsstrahlung emissions for a plastic target for intensities of 10^(20)-10^(23)W/cm^(2).We present angular distribution plots where the NCS emission is seen to dominate at intensities greater than 5×10^(21)W/cm^(2)and the target design is seen to successfully divert the bremsstrahlung signal away from the NCS lobe regions,making the experimental observation of nonlinear inverse Compton scattering at lower intensities more likely.
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supported by the National Natural Science Foundation of China(Grant Nos.62075056 and 61927815)the Natural Science Foundation of Hebei Province(Grant Nos.F2023202082 and F2022202035)。
文摘Based on a 4f system,a 0?reflector and a single laser diode side-pump amplifier,a new amplifier is designed to compensate the spherical aberration of the amplified laser generated by a single laser diode side-pump amplifier and enhance the power of the amplified laser.Furthermore,the role of the 4f system in the passive spherical aberration compensation and its effect on the amplified laser are discussed in detail.The results indicate that the amplification efficiency is enhanced by incorporating a 4f system in a double-pass amplifier and placing a 0?reflector only at the focal point of the single-pass amplified laser.This method also effectively uses the heat from the gain medium(neodymiumdoped yttrium aluminium garnet)of the amplifier to compensate the spherical aberration of the amplified laser.
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funding for the DAS Interrogator.Finally,Oliver Gerberding and Katharina-Sophie Isleif acknowledge support of the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)under Germany’s Excellence Strategy-EXC 2121‘Quantum Universe’-390833306.
文摘Measurements of the bunch arrival times at the European X-ray free-electron laser show noise contributions in the spectral range between 0.05 and 0.5 Hz with peak-to-peak jitter of up to 25 fs.Correlation with distributed acoustic sensing measurements confirms the seismic origin.The seismic noise in this frequency band is known to be oceangenerated microseism.Both primary and secondary ocean-generated microseisms were identified using seismometers and a numerical ocean wave model.Whereas secondary microseism has a strong impact on the bunch arrival time,primary microseism has no notable effect.Rayleigh waves cause the effect,while Love waves have minimal impact.In the presented cases,the noise originates from the North Atlantic and/or the North Sea.The amplitude of the noise depends on the local weather conditions and is much stronger in winter.Ocean-generated microseism is a significant bottleneck that must be addressed to achieve femtosecond bunch arrival time stability in the sub-Hz regime.
