We report on an experiment performed at the FLASH2 free-electron laser(FEL)aimed at producing warm dense matter via soft x-ray isochoric heating.In the experiment,we focus on study of the ions emitted during the soft ...We report on an experiment performed at the FLASH2 free-electron laser(FEL)aimed at producing warm dense matter via soft x-ray isochoric heating.In the experiment,we focus on study of the ions emitted during the soft x-ray ablation process using time-of-flight electron multipliers and a shifted Maxwell–Boltzmann velocity distribution model.We find that most emitted ions are thermal,but that some impurities chemisorbed on the target surface,such as protons,are accelerated by the electrostatic field created in the plasma by escaped electrons.The morphology of the complex crater structure indicates the presence of several ion groups with varying temperatures.We find that the ion sound velocity is controlled by the ion temperature and show how the ion yield depends on the FEL radiation attenuation length in different materials.展开更多
We present here experimental results on the optimization of the mega-electronvolt ion source from the target front surface by using relativistic(10^(18)W/cm^(2))interactions with ultra-short laser pulses(50 fs).The so...We present here experimental results on the optimization of the mega-electronvolt ion source from the target front surface by using relativistic(10^(18)W/cm^(2))interactions with ultra-short laser pulses(50 fs).The source perturbation in the accelerated proton/ion beam was primarily controlled by the addition of a pre-pulse to main pulse contrast ratio.The 2D particle-in-cell simulations agreed well with the observed experimental results for the ion source perturbation and mitigation.This work provides insights into ion source perturbations(temporal and spatial)and the need to control them in intense laser–plasma interactions.Our results may assist in the efficient guiding of proton/ion beams to the core of fusion fuel or of ions in cancer therapy.展开更多
A real-time ion spectrometer mainly based on a high-resolution Thomson parabola and a plastic scintillator is designed and developed.The spectrometer is calibrated by protons from an electrostatic accelerator.The feas...A real-time ion spectrometer mainly based on a high-resolution Thomson parabola and a plastic scintillator is designed and developed.The spectrometer is calibrated by protons from an electrostatic accelerator.The feasibility and reliability of the diagnostics are demonstrated in laser-driven ion acceleration experiments performed on the XL-II laser facility.The proton spectrum extrapolated from the scintillator data is in excellent agreement with the CR39 spectrum in terms of beam temperature and the cutoff energy.This real-time spectrometer allows an online measurement of the ion spectra in single shot,which enables efficient and statistical studies and applications in high-repetition-rate laser acceleration experiments.展开更多
X-ray absorption spectroscopy is a well-accepted diagnostic for experimental studies of warm dense matter.It requires a short-lived X-ray source of sufficiently high emissivity and without characteristic lines in the ...X-ray absorption spectroscopy is a well-accepted diagnostic for experimental studies of warm dense matter.It requires a short-lived X-ray source of sufficiently high emissivity and without characteristic lines in the spectral range of interest.In the present work,we discuss how to choose an optimum material and thickness to get a bright source in the wavelength range 2A–6A(∼2 keV to 6 keV)by considering relatively low-Z elements.We demonstrate that the highest emissivity of solid aluminum and silicon foil targets irradiated with a 1-ps high-contrast sub-kJ laser pulse is achieved when the target thickness is close to 10μm.An outer plastic layer can increase the emissivity even further.展开更多
In this paper we review the provision of the laser diagnostics that are installed on the Vulcan laser facility. We will present strategies for dealing with the energy of high energy systems and with ways of handling t...In this paper we review the provision of the laser diagnostics that are installed on the Vulcan laser facility. We will present strategies for dealing with the energy of high energy systems and with ways of handling the beam sizes of the lasers. We present data captured during typical experimental campaigns to demonstrate their reliability and variation in shot to shot values.展开更多
The design of ellipsoidal plasma mirrors(EPMs)for the PEARL laser facility is presented.The EPMs achieve a magnification of 0.32 in focal spot size,and the corresponding increase in focused intensity is expected to be...The design of ellipsoidal plasma mirrors(EPMs)for the PEARL laser facility is presented.The EPMs achieve a magnification of 0.32 in focal spot size,and the corresponding increase in focused intensity is expected to be about 8.Designing and implementing such focusing optics for short-pulse(<100 fs)systems paves the way for their use in future high-power facilities,where they can be used to achieve intensities beyond 1023W/cm^(2).A retro-imaging-based target alignment system is also described,which is used to align solid targets at the output of the ellispoidal mirrors(with a numerical aperture of 0.75 in this case).展开更多
This article describes the fabrication of a suite of laser targets by the Target Fabrication group in the Central Laser Facility(CLF), STFC Rutherford Appleton Laboratory for the first academic-access experiment on th...This article describes the fabrication of a suite of laser targets by the Target Fabrication group in the Central Laser Facility(CLF), STFC Rutherford Appleton Laboratory for the first academic-access experiment on the Orion laser facility(Hopps et al., Appl. Opt. 52, 3597–3601(2013)) at Atomic Weapons Establishment(AWE). This experiment, part of the POLAR project(Falize et al., Astrophys. Space Sci. 336, 81–85(2011); Busschaert et al., New J. Phys. 15, 035020(2013)),studied conditions relevant to the radiation-hydrodynamic processes occurring in a remarkable class of astrophysical star systems known as magnetic cataclysmic variables. A large number of complex fabrication technologies and research and development activities were required to field a total of 80 high-specification targets. Target design and fabrication procedures are described and initial alignment and characterization data are discussed.展开更多
The next generation of high-power lasers enables repetition of experiments at orders of magnitude higher frequency than what was possible using the prior generation.Facilities requiring human intervention between lase...The next generation of high-power lasers enables repetition of experiments at orders of magnitude higher frequency than what was possible using the prior generation.Facilities requiring human intervention between laser repetitions need to adapt in order to keep pace with the new laser technology.A distributed networked control system can enable laboratory-wide automation and feedback control loops.These higher-repetition-rate experiments will create enormous quantities of data.A consistent approach to managing data can increase data accessibility,reduce repetitive data-software development and mitigate poorly organized metadata.An opportunity arises to share knowledge of improvements to control and data infrastructure currently being undertaken.We compare platforms and approaches to state-of-the-art control systems and data management at high-power laser facilities,and we illustrate these topics with case studies from our community.展开更多
A machine learning model was created to predict the electron spectrum generated by a GeV-class laser wakefield accelerator.The model was constructed from variational convolutional neural networks,which mapped the resu...A machine learning model was created to predict the electron spectrum generated by a GeV-class laser wakefield accelerator.The model was constructed from variational convolutional neural networks,which mapped the results of secondary laser and plasma diagnostics to the generated electron spectrum.An ensemble of trained networks was used to predict the electron spectrum and to provide an estimation of the uncertainty of that prediction.It is anticipated that this approach will be useful for inferring the electron spectrum prior to undergoing any process that can alter or destroy the beam.In addition,the model provides insight into the scaling of electron beam properties due to stochastic fluctuations in the laser energy and plasma electron density.展开更多
We present the development and characterization of a high-stability,multi-material,multi-thickness tape-drive target for laser-driven acceleration at repetition rates of up to 100 Hz.The tape surface position was meas...We present the development and characterization of a high-stability,multi-material,multi-thickness tape-drive target for laser-driven acceleration at repetition rates of up to 100 Hz.The tape surface position was measured to be stable on the sub-micrometre scale,compatible with the high-numerical aperture focusing geometries required to achieve relativistic intensity interactions with the pulse energy available in current multi-Hz and near-future higher repetition-rate lasers(>kHz).Long-term drift was characterized at 100 Hz demonstrating suitability for operation over extended periods.The target was continuously operated at up to 5 Hz in a recent experiment for 70,000 shots without intervention by the experimental team,with the exception of tape replacement,producing the largest data-set of relativistically intense laser–solid foil measurements to date.This tape drive provides robust targetry for the generation and study of high-repetitionrate ion beams using next-generation high-power laser systems,also enabling wider applications of laser-driven proton sources.展开更多
The interaction of relativistically intense lasers with opaque targets represents a highly non-linear,multi-dimensional parameter space.This limits the utility of sequential 1D scanning of experimental parameters for ...The interaction of relativistically intense lasers with opaque targets represents a highly non-linear,multi-dimensional parameter space.This limits the utility of sequential 1D scanning of experimental parameters for the optimization of secondary radiation,although to-date this has been the accepted methodology due to low data acquisition rates.High repetition-rate(HRR)lasers augmented by machine learning present a valuable opportunity for efficient source optimization.Here,an automated,HRR-compatible system produced high-fidelity parameter scans,revealing the influence of laser intensity on target pre-heating and proton generation.A closed-loop Bayesian optimization of maximum proton energy,through control of the laser wavefront and target position,produced proton beams with equivalent maximum energy to manually optimized laser pulses but using only 60%of the laser energy.This demonstration of automated optimization of laser-driven proton beams is a crucial step towards deeper physical insight and the construction of future radiation sources.展开更多
In this paper we review the design and development of a 100 J, 10 Hz nanosecond pulsed laser, codenamed DiPOLE100 X,being built at the Central Laser Facility(CLF). This 1 kW average power diode-pumped solid-state lase...In this paper we review the design and development of a 100 J, 10 Hz nanosecond pulsed laser, codenamed DiPOLE100 X,being built at the Central Laser Facility(CLF). This 1 kW average power diode-pumped solid-state laser(DPSSL) is based on a master oscillator power amplifier(MOPA) design, which includes two cryogenic gas cooled amplifier stages based on DiPOLE multi-slab ceramic Yb:YAG amplifier technology developed at the CLF. The laser will produce pulses between 2 and 15 ns in duration with precise, arbitrarily selectable shapes, at pulse repetition rates up to 10 Hz, allowing real-time shape optimization for compression experiments. Once completed, the laser will be delivered to the European X-ray Free Electron Laser(XFEL) facility in Germany as a UK-funded contribution in kind, where it will be used to study extreme states of matter at the High Energy Density(HED) instrument.展开更多
We report on the successful demonstration of a 150 J nanosecond pulsed cryogenic gas cooled,diode-pumped multi-slab Yb:YAG laser operating at 1 Hz.To the best of our knowledge,this is the highest energy ever recorded ...We report on the successful demonstration of a 150 J nanosecond pulsed cryogenic gas cooled,diode-pumped multi-slab Yb:YAG laser operating at 1 Hz.To the best of our knowledge,this is the highest energy ever recorded for a diodepumped laser system.展开更多
A petawatt facility fully based on noncollinear optical parametric chirped pulse amplification(NOPCPA)technology,Vulcan OPPEL(Vulcan OPCPA PEtawatt Laser),is presented.This system will be coupled with the existing hyb...A petawatt facility fully based on noncollinear optical parametric chirped pulse amplification(NOPCPA)technology,Vulcan OPPEL(Vulcan OPCPA PEtawatt Laser),is presented.This system will be coupled with the existing hybridCPA/OPCPA VULCAN laser system(500 J,500 fs beamline;250 J,ns regime beamline)based on Nd:glass amplification.Its pulse duration(20 times shorter)combined with the system design will allow the auxiliary beamline and its secondary sources to be used as probe beams for longer pulses and their interactions with targets.The newly designed system will be mainly dedicated to electron beam generation,but could also be used to perform a variety of particle acceleration and optical radiation detection experimental campaigns.In this communication,we present the entire beamline design discussing the technology choices and the design supported by extensive simulations for each system section.Finally,we present experimental results and details of our commissioned NOPCPA picosecond front end,delivering 1.5 mJ,~180 nm(1/e^(2))of bandwidth compressed to sub-15 fs.展开更多
A multichannel calorimeter system is designed and constructed which is capable of delivering single-shot and broadband spectral measurement of terahertz(THz) radiation generated in intense laser–plasma interactions. ...A multichannel calorimeter system is designed and constructed which is capable of delivering single-shot and broadband spectral measurement of terahertz(THz) radiation generated in intense laser–plasma interactions. The generation mechanism of backward THz radiation(BTR) is studied by using the multichannel calorimeter system in an intense picosecond laser–solid interaction experiment. The dependence of the BTR energy and spectrum on laser energy, target thickness and pre-plasma scale length is obtained. These results indicate that coherent transition radiation is responsible for the low-frequency component(<1 THz) of BTR. It is also observed that a large-scale pre-plasma primarily enhances the high-frequency component(>3 THz) of BTR.展开更多
There are several petawatt-scale laser facilities around the world and the fidelity of the pulses to target is critical in achieving the highest focused intensities and the highest possible contrast. The United Kingdo...There are several petawatt-scale laser facilities around the world and the fidelity of the pulses to target is critical in achieving the highest focused intensities and the highest possible contrast. The United Kingdom has three such laser facilities which are currently open for access to the academic community: Orion at AWE, Aldermaston and Vulcan & Astra-Gemini at the Central Laser Facility(CLF), STFC(Science and Technology Facilities Council)Rutherford Appleton Laboratory(RAL). These facilities represent the two main classes of petawatt facilities: the mixed OPCPA/Nd:glass high-energy systems of Orion and Vulcan and the ultra-short-pulse Ti:Sapphire system of AstraGemini. Many of the techniques used to enhance and control the pulse generation and delivery to target have been pioneered on these facilities. In this paper, we present the system designs which make this possible and discuss the contrast enhancement schemes that have been implemented.展开更多
Giant electromagnetic pulses(EMP) generated during the interaction of high-power lasers with solid targets can seriously degrade electrical measurements and equipment. EMP emission is caused by the acceleration of hot...Giant electromagnetic pulses(EMP) generated during the interaction of high-power lasers with solid targets can seriously degrade electrical measurements and equipment. EMP emission is caused by the acceleration of hot electrons inside the target, which produce radiation across a wide band from DC to terahertz frequencies. Improved understanding and control of EMP is vital as we enter a new era of high repetition rate, high intensity lasers(e.g. the Extreme Light Infrastructure).We present recent data from the VULCAN laser facility that demonstrates how EMP can be readily and effectively reduced. Characterization of the EMP was achieved using B-dot and D-dot probes that took measurements for a range of different target and laser parameters. We demonstrate that target stalk geometry, material composition, geodesic path length and foil surface area can all play a significant role in the reduction of EMP. A combination of electromagnetic wave and 3 D particle-in-cell simulations is used to inform our conclusions about the effects of stalk geometry on EMP,providing an opportunity for comparison with existing charge separation models.展开更多
Filamentary structures can form within the beam of protons accelerated during the interaction of an intense laser pulse with an ultrathin foil target. Such behaviour is shown to be dependent upon the formation time of...Filamentary structures can form within the beam of protons accelerated during the interaction of an intense laser pulse with an ultrathin foil target. Such behaviour is shown to be dependent upon the formation time of quasi-static magnetic field structures throughout the target volume and the extent of the rear surface proton expansion over the same period.This is observed via both numerical and experimental investigations. By controlling the intensity profile of the laser drive,via the use of two temporally separated pulses, both the initial rear surface proton expansion and magnetic field formation time can be varied, resulting in modification to the degree of filamentary structure present within the laser-driven proton beam.展开更多
The first demonstration of laser action in ruby was made in 1960 by T.H.Maiman of Hughes Research Laboratories,USA.Many laboratories worldwide began the search for lasers using different materials,operating at differe...The first demonstration of laser action in ruby was made in 1960 by T.H.Maiman of Hughes Research Laboratories,USA.Many laboratories worldwide began the search for lasers using different materials,operating at different wavelengths.In the UK,academia,industry and the central laboratories took up the challenge from the earliest days to develop these systems for a broad range of applications.This historical review looks at the contribution the UK has made to the advancement of the technology,the development of systems and components and their exploitation over the last 60 years.展开更多
We report results and modelling of an experiment performed at the Target Area West Vulcan laser facility,aimed at investigating laser±plasma interaction in conditions that are of interest for the shock ignition s...We report results and modelling of an experiment performed at the Target Area West Vulcan laser facility,aimed at investigating laser±plasma interaction in conditions that are of interest for the shock ignition scheme in inertial confinement fusion(ICF),that is,laser intensity higher than 10^(16) W/cm^(2) impinging on a hot(T>1 keV),inhomogeneous and long scalelength pre-formed plasma.Measurements show a significant stimulated Raman scattering(SRS)backscattering(;%-20%of laser energy)driven at low plasma densities and no signatures of two-plasmon decay(TPD)/SRS driven at the quarter critical density region.Results are satisfactorily reproduced by an analytical model accounting for the convective SRS growth in independent laser speckles,in conditions where the reflectivity is dominated by the contribution from the most intense speckles,where SRS becomes saturated.Analytical and kinetic simulations well reproduce the onset of SRS at low plasma densities in a regime strongly affected by non-linear Landau damping and by filamentation of the most intense laser speckles.The absence of TPD/SRS at higher densities is explained by pump depletion and plasma smoothing driven by filamentation.The prevalence of laser coupling in the low-density profile justifies the low temperature measured for hot electrons(7-12 keV),which is well reproduced by numerical simulations.展开更多
文摘We report on an experiment performed at the FLASH2 free-electron laser(FEL)aimed at producing warm dense matter via soft x-ray isochoric heating.In the experiment,we focus on study of the ions emitted during the soft x-ray ablation process using time-of-flight electron multipliers and a shifted Maxwell–Boltzmann velocity distribution model.We find that most emitted ions are thermal,but that some impurities chemisorbed on the target surface,such as protons,are accelerated by the electrostatic field created in the plasma by escaped electrons.The morphology of the complex crater structure indicates the presence of several ion groups with varying temperatures.We find that the ion sound velocity is controlled by the ion temperature and show how the ion yield depends on the FEL radiation attenuation length in different materials.
基金support from the SERB Imprint Project No.IMP/2019/000275
文摘We present here experimental results on the optimization of the mega-electronvolt ion source from the target front surface by using relativistic(10^(18)W/cm^(2))interactions with ultra-short laser pulses(50 fs).The source perturbation in the accelerated proton/ion beam was primarily controlled by the addition of a pre-pulse to main pulse contrast ratio.The 2D particle-in-cell simulations agreed well with the observed experimental results for the ion source perturbation and mitigation.This work provides insights into ion source perturbations(temporal and spatial)and the need to control them in intense laser–plasma interactions.Our results may assist in the efficient guiding of proton/ion beams to the core of fusion fuel or of ions in cancer therapy.
基金by the National Natural Science Foundation of China under Grant Nos 10905092(Young Scientists Fund),10925421,10974250,and 10935002the National Basic Research Program of China under Grant No 2007CB815102the Fundamental Research Funds for the Central Universities.
文摘A real-time ion spectrometer mainly based on a high-resolution Thomson parabola and a plastic scintillator is designed and developed.The spectrometer is calibrated by protons from an electrostatic accelerator.The feasibility and reliability of the diagnostics are demonstrated in laser-driven ion acceleration experiments performed on the XL-II laser facility.The proton spectrum extrapolated from the scintillator data is in excellent agreement with the CR39 spectrum in terms of beam temperature and the cutoff energy.This real-time spectrometer allows an online measurement of the ion spectra in single shot,which enables efficient and statistical studies and applications in high-repetition-rate laser acceleration experiments.
基金The study was supported financially by the Russian Foundation for Basic Research(Grant No.20-02-00790)the Joint Institute for High Temperatures of the Russian Academy of Sciences(Topic Grant No.01201357846)The UK team received financial support from the Engineering and Physical Sciences Research Council(Grant Nos.EP/L01663X/1 and EP/H012605/1).
文摘X-ray absorption spectroscopy is a well-accepted diagnostic for experimental studies of warm dense matter.It requires a short-lived X-ray source of sufficiently high emissivity and without characteristic lines in the spectral range of interest.In the present work,we discuss how to choose an optimum material and thickness to get a bright source in the wavelength range 2A–6A(∼2 keV to 6 keV)by considering relatively low-Z elements.We demonstrate that the highest emissivity of solid aluminum and silicon foil targets irradiated with a 1-ps high-contrast sub-kJ laser pulse is achieved when the target thickness is close to 10μm.An outer plastic layer can increase the emissivity even further.
文摘In this paper we review the provision of the laser diagnostics that are installed on the Vulcan laser facility. We will present strategies for dealing with the energy of high energy systems and with ways of handling the beam sizes of the lasers. We present data captured during typical experimental campaigns to demonstrate their reliability and variation in shot to shot values.
基金The results of Project LQ1606 were obtained with the financial support of the Ministry of Education,Youths and Sports as part of targeted support from the National Programme of Sustainability II.This research was also sponsored by the Czech Science Foundation(Project No.18-09560S)by the project High Field Initiative(CZ.02.1.01/0.0/0.0/15_003/0000449)from the European Regional Development Fund(HIFI),by the project on Advanced Research Using High Intensity Laser Produced Photons and Particles(No.CZ.02.1.01/0.0/0.0/16019/0000789)from the European Regional Development Fund(ADONIS)+1 种基金by theMinistry of Education and Science of the Russian Federation under Contract No.14.Z50.31.0007.The work was also supported by the Ministry of Education and Science of the Russian Federation(FTP Grant#14.607.21.0196,Project ID:RFMEFI60717X0196)The work of JIHT RAS team on X-ray measurements and analysis was done with financial support fromthe Russian Science Foundation(Grant#14-50-00124).
文摘The design of ellipsoidal plasma mirrors(EPMs)for the PEARL laser facility is presented.The EPMs achieve a magnification of 0.32 in focal spot size,and the corresponding increase in focused intensity is expected to be about 8.Designing and implementing such focusing optics for short-pulse(<100 fs)systems paves the way for their use in future high-power facilities,where they can be used to achieve intensities beyond 1023W/cm^(2).A retro-imaging-based target alignment system is also described,which is used to align solid targets at the output of the ellispoidal mirrors(with a numerical aperture of 0.75 in this case).
文摘This article describes the fabrication of a suite of laser targets by the Target Fabrication group in the Central Laser Facility(CLF), STFC Rutherford Appleton Laboratory for the first academic-access experiment on the Orion laser facility(Hopps et al., Appl. Opt. 52, 3597–3601(2013)) at Atomic Weapons Establishment(AWE). This experiment, part of the POLAR project(Falize et al., Astrophys. Space Sci. 336, 81–85(2011); Busschaert et al., New J. Phys. 15, 035020(2013)),studied conditions relevant to the radiation-hydrodynamic processes occurring in a remarkable class of astrophysical star systems known as magnetic cataclysmic variables. A large number of complex fabrication technologies and research and development activities were required to field a total of 80 high-specification targets. Target design and fabrication procedures are described and initial alignment and characterization data are discussed.
基金A.J.acknowledges the support from DOE Grant#DESC0016804.
文摘The next generation of high-power lasers enables repetition of experiments at orders of magnitude higher frequency than what was possible using the prior generation.Facilities requiring human intervention between laser repetitions need to adapt in order to keep pace with the new laser technology.A distributed networked control system can enable laboratory-wide automation and feedback control loops.These higher-repetition-rate experiments will create enormous quantities of data.A consistent approach to managing data can increase data accessibility,reduce repetitive data-software development and mitigate poorly organized metadata.An opportunity arises to share knowledge of improvements to control and data infrastructure currently being undertaken.We compare platforms and approaches to state-of-the-art control systems and data management at high-power laser facilities,and we illustrate these topics with case studies from our community.
基金supported by UK STFC ST/V001639/1,UK EPSRC EP/V049577/1 and EP/V044397/1Horizon 2020 funding under European Research Council(ERC)Grant Agreement No.682399+1 种基金support from the Royal Society URF-R1221874support from US DOE grant DESC0016804
文摘A machine learning model was created to predict the electron spectrum generated by a GeV-class laser wakefield accelerator.The model was constructed from variational convolutional neural networks,which mapped the results of secondary laser and plasma diagnostics to the generated electron spectrum.An ensemble of trained networks was used to predict the electron spectrum and to provide an estimation of the uncertainty of that prediction.It is anticipated that this approach will be useful for inferring the electron spectrum prior to undergoing any process that can alter or destroy the beam.In addition,the model provides insight into the scaling of electron beam properties due to stochastic fluctuations in the laser energy and plasma electron density.
基金Special thanks go to the staff at the Central Laser Facility who provided laser operational support,mechanical and electrical support and computational and administrative support throughout the experiment.We acknowledge funding from UK STFC,Grant Nos.ST/P002021/1 and ST/V001639/1U.S.DOE Office of Science,Fusion Energy Sciences under FWP No.100182+2 种基金in part by the National Science Foundation under Grant No.1632708G.D.G.acknowledges support from the DOE NNSA SSGF program under DE-NA0003960This work has been partially supported by the project Advanced Research Using High-intensity Laser-produced Photons and Particles(CZ.02.1.01/0.0/0.0/16_019/0000789)from the European Regional Development Fund(ADONIS).
文摘We present the development and characterization of a high-stability,multi-material,multi-thickness tape-drive target for laser-driven acceleration at repetition rates of up to 100 Hz.The tape surface position was measured to be stable on the sub-micrometre scale,compatible with the high-numerical aperture focusing geometries required to achieve relativistic intensity interactions with the pulse energy available in current multi-Hz and near-future higher repetition-rate lasers(>kHz).Long-term drift was characterized at 100 Hz demonstrating suitability for operation over extended periods.The target was continuously operated at up to 5 Hz in a recent experiment for 70,000 shots without intervention by the experimental team,with the exception of tape replacement,producing the largest data-set of relativistically intense laser–solid foil measurements to date.This tape drive provides robust targetry for the generation and study of high-repetitionrate ion beams using next-generation high-power laser systems,also enabling wider applications of laser-driven proton sources.
基金support from the UK STFC grants ST/V001639/1 with the XFEL Physical Sciences Hub and ST/P002021/1the UK EPSRC grants EP/V049577/1 and EP/R006202/1+5 种基金as well as the U.S.DOE Office of Science,Fusion Energy Sciences under FWP No.100182in part by the National Science Foundation under Grant No.1632708 and Award No.PHY–1903414M.J.V.S.acknowledges support from the Royal Society URFR1221874support from the DOE NNSA SSGF program under DE-NA0003960support from the U.S.DOE grant DESC0016804support from the project‘Advanced research using high-intensity laser-produced photons and particles’(CZ.02.1.01/0.0/0.0/16_019/0000789)from the European Regional Development Fund(ADONIS)。
文摘The interaction of relativistically intense lasers with opaque targets represents a highly non-linear,multi-dimensional parameter space.This limits the utility of sequential 1D scanning of experimental parameters for the optimization of secondary radiation,although to-date this has been the accepted methodology due to low data acquisition rates.High repetition-rate(HRR)lasers augmented by machine learning present a valuable opportunity for efficient source optimization.Here,an automated,HRR-compatible system produced high-fidelity parameter scans,revealing the influence of laser intensity on target pre-heating and proton generation.A closed-loop Bayesian optimization of maximum proton energy,through control of the laser wavefront and target position,produced proton beams with equivalent maximum energy to manually optimized laser pulses but using only 60%of the laser energy.This demonstration of automated optimization of laser-driven proton beams is a crucial step towards deeper physical insight and the construction of future radiation sources.
基金funded by the NEWTON China–UK Joint Research Project on Laser-driven Ion Acceleration and Novel Terahertz Radiation
文摘In this paper we review the design and development of a 100 J, 10 Hz nanosecond pulsed laser, codenamed DiPOLE100 X,being built at the Central Laser Facility(CLF). This 1 kW average power diode-pumped solid-state laser(DPSSL) is based on a master oscillator power amplifier(MOPA) design, which includes two cryogenic gas cooled amplifier stages based on DiPOLE multi-slab ceramic Yb:YAG amplifier technology developed at the CLF. The laser will produce pulses between 2 and 15 ns in duration with precise, arbitrarily selectable shapes, at pulse repetition rates up to 10 Hz, allowing real-time shape optimization for compression experiments. Once completed, the laser will be delivered to the European X-ray Free Electron Laser(XFEL) facility in Germany as a UK-funded contribution in kind, where it will be used to study extreme states of matter at the High Energy Density(HED) instrument.
文摘We report on the successful demonstration of a 150 J nanosecond pulsed cryogenic gas cooled,diode-pumped multi-slab Yb:YAG laser operating at 1 Hz.To the best of our knowledge,this is the highest energy ever recorded for a diodepumped laser system.
基金financial support of the European Union’s Horizon 2020 research and innovation programme under grant agreement No.654148(Laserlab Europe)the Euratom research and training program 2014–2018 under grant agreement No.633053+1 种基金the Fundacao para a Ciencia e a Tecnologia(FCT,Lisboa)under grants No.PD/BD/114327/2016framework of the Advanced Program in Plasma Science and Engineering(APPLAuSE,sponsored by FCT under grant No.PD/00505/2012)at Instituto Superior Tecnico(IST)。
文摘A petawatt facility fully based on noncollinear optical parametric chirped pulse amplification(NOPCPA)technology,Vulcan OPPEL(Vulcan OPCPA PEtawatt Laser),is presented.This system will be coupled with the existing hybridCPA/OPCPA VULCAN laser system(500 J,500 fs beamline;250 J,ns regime beamline)based on Nd:glass amplification.Its pulse duration(20 times shorter)combined with the system design will allow the auxiliary beamline and its secondary sources to be used as probe beams for longer pulses and their interactions with targets.The newly designed system will be mainly dedicated to electron beam generation,but could also be used to perform a variety of particle acceleration and optical radiation detection experimental campaigns.In this communication,we present the entire beamline design discussing the technology choices and the design supported by extensive simulations for each system section.Finally,we present experimental results and details of our commissioned NOPCPA picosecond front end,delivering 1.5 mJ,~180 nm(1/e^(2))of bandwidth compressed to sub-15 fs.
基金supported by the Newton China–UK joint research grant on laser–ion acceleration and novel terahertz radiationEPSRC grant EP/K022415/1 on advanced laser–ion acceleration strategies toward next generation healthcare and EPSRC grant EP/R006202/1+2 种基金supported by the National NaturalScience Foundation of China(Nos.11520101003 and11861121001)the Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDB16010200 and XDB07030300)support from the National Postdoctoral Program for Innovative Talents(No.BX201600106)
文摘A multichannel calorimeter system is designed and constructed which is capable of delivering single-shot and broadband spectral measurement of terahertz(THz) radiation generated in intense laser–plasma interactions. The generation mechanism of backward THz radiation(BTR) is studied by using the multichannel calorimeter system in an intense picosecond laser–solid interaction experiment. The dependence of the BTR energy and spectrum on laser energy, target thickness and pre-plasma scale length is obtained. These results indicate that coherent transition radiation is responsible for the low-frequency component(<1 THz) of BTR. It is also observed that a large-scale pre-plasma primarily enhances the high-frequency component(>3 THz) of BTR.
文摘There are several petawatt-scale laser facilities around the world and the fidelity of the pulses to target is critical in achieving the highest focused intensities and the highest possible contrast. The United Kingdom has three such laser facilities which are currently open for access to the academic community: Orion at AWE, Aldermaston and Vulcan & Astra-Gemini at the Central Laser Facility(CLF), STFC(Science and Technology Facilities Council)Rutherford Appleton Laboratory(RAL). These facilities represent the two main classes of petawatt facilities: the mixed OPCPA/Nd:glass high-energy systems of Orion and Vulcan and the ultra-short-pulse Ti:Sapphire system of AstraGemini. Many of the techniques used to enhance and control the pulse generation and delivery to target have been pioneered on these facilities. In this paper, we present the system designs which make this possible and discuss the contrast enhancement schemes that have been implemented.
基金funding from EPSRC grants EP/L01663X/1 and EP/L000644/1the Newton UK grant+1 种基金the National Natural Science Foundation of China NSFC/11520101003the LLNL Academic Partnership in ICF
文摘Giant electromagnetic pulses(EMP) generated during the interaction of high-power lasers with solid targets can seriously degrade electrical measurements and equipment. EMP emission is caused by the acceleration of hot electrons inside the target, which produce radiation across a wide band from DC to terahertz frequencies. Improved understanding and control of EMP is vital as we enter a new era of high repetition rate, high intensity lasers(e.g. the Extreme Light Infrastructure).We present recent data from the VULCAN laser facility that demonstrates how EMP can be readily and effectively reduced. Characterization of the EMP was achieved using B-dot and D-dot probes that took measurements for a range of different target and laser parameters. We demonstrate that target stalk geometry, material composition, geodesic path length and foil surface area can all play a significant role in the reduction of EMP. A combination of electromagnetic wave and 3 D particle-in-cell simulations is used to inform our conclusions about the effects of stalk geometry on EMP,providing an opportunity for comparison with existing charge separation models.
基金supported by EPSRC(grants EP/J003832/1,EP/R006202/1,EP/P007082/1 and EP/K022415/1)the European Unions Horizon 2020 research and innovation program(grant agreement No.654148 Laserlab-Europe)EPSRC grant EP/G054940/1
文摘Filamentary structures can form within the beam of protons accelerated during the interaction of an intense laser pulse with an ultrathin foil target. Such behaviour is shown to be dependent upon the formation time of quasi-static magnetic field structures throughout the target volume and the extent of the rear surface proton expansion over the same period.This is observed via both numerical and experimental investigations. By controlling the intensity profile of the laser drive,via the use of two temporally separated pulses, both the initial rear surface proton expansion and magnetic field formation time can be varied, resulting in modification to the degree of filamentary structure present within the laser-driven proton beam.
文摘The first demonstration of laser action in ruby was made in 1960 by T.H.Maiman of Hughes Research Laboratories,USA.Many laboratories worldwide began the search for lasers using different materials,operating at different wavelengths.In the UK,academia,industry and the central laboratories took up the challenge from the earliest days to develop these systems for a broad range of applications.This historical review looks at the contribution the UK has made to the advancement of the technology,the development of systems and components and their exploitation over the last 60 years.
基金financial support from the LASERLAB-EUROPE Access to Research Infrastructure activity within the EC’s seventh Framework Program(Application No.18110033)carried out within the framework of the EUROfusion Enabling research projects AWP19-20-ENR-IFE19.CEA01 and AWP21-ENR-01-CEA-02+2 种基金funding from the Euratom research and training programme 20192020 and 2021-2025 under grant No.633053financial support from the CNR-funded Italian research Network ELI-Italy(D.M.No.63108.08.2016)the Czech Ministry of Education,Youth and Sports,project LTT17015。
文摘We report results and modelling of an experiment performed at the Target Area West Vulcan laser facility,aimed at investigating laser±plasma interaction in conditions that are of interest for the shock ignition scheme in inertial confinement fusion(ICF),that is,laser intensity higher than 10^(16) W/cm^(2) impinging on a hot(T>1 keV),inhomogeneous and long scalelength pre-formed plasma.Measurements show a significant stimulated Raman scattering(SRS)backscattering(;%-20%of laser energy)driven at low plasma densities and no signatures of two-plasmon decay(TPD)/SRS driven at the quarter critical density region.Results are satisfactorily reproduced by an analytical model accounting for the convective SRS growth in independent laser speckles,in conditions where the reflectivity is dominated by the contribution from the most intense speckles,where SRS becomes saturated.Analytical and kinetic simulations well reproduce the onset of SRS at low plasma densities in a regime strongly affected by non-linear Landau damping and by filamentation of the most intense laser speckles.The absence of TPD/SRS at higher densities is explained by pump depletion and plasma smoothing driven by filamentation.The prevalence of laser coupling in the low-density profile justifies the low temperature measured for hot electrons(7-12 keV),which is well reproduced by numerical simulations.