It has been said that,once a bomb casing has fractured, "detonation gases will then stream around the fragments or bypass them,and the acceleration process stops there." However,while apparently copious gas ...It has been said that,once a bomb casing has fractured, "detonation gases will then stream around the fragments or bypass them,and the acceleration process stops there." However,while apparently copious gas flow through casing fractures indicates some pressure release,it is also an indication of significant gas drive pressure,post casing fracture.This paper shows two approaches to the problem of calculating the actual loss of drive.One presents first-order analytical calculations,in cylindrical geometry,of pressure loss to the inside surface of a fractured casing.The second shows the modelling of a selected example in the CTH code.Both approaches reveal that gas escape,while occurring at its own soundspeed relative to the adjacent casing fragments,has to compete with rapid radial expansion of the casing.Together with some historic experiments now publicly available,our calculations indicate that post-fracture casing fragment acceleration is,for most systems,unlikely to be reduced significantly.展开更多
Three-dimensional(3D)hydrodynamic numerical simulations of laser driven thin-shell gas-filled microballoons have been carried out using the computer code MULTI-3D[Ramis et al.,Phys.Plasmas 21,082710(2014)].The studied...Three-dimensional(3D)hydrodynamic numerical simulations of laser driven thin-shell gas-filled microballoons have been carried out using the computer code MULTI-3D[Ramis et al.,Phys.Plasmas 21,082710(2014)].The studied configuration corresponds to experiments carried at the ORION laser facility[Hopps et al.,Plasma Phys.Controlled Fusion 57,064002(2015)].The MULTI-3D code solves single-temperature hydrodynamics,electron heat transport,and 3D ray tracing with inverse bremsstrahlung absorption on unstructured Lagrangian grids.Special emphasis has been placed on the genuine 3D effects that are inaccessible to calculations using simplified 1D or 2D geometries.These include the consequences of(i)a finite number of laser beams(10 in the experimental campaign),(ii)intensity irregularities in the beam crosssectional profiles,(iii)laser beam misalignments,and(iv)power imbalance between beams.The consequences of these imperfections have been quantified by post-processing the numerical results in terms of capsule nonuniformities(synthetic emission and absorption images)and implosion efficiency(convergence ratio and neutron yield).Statistical analysis of these outcomes allows determination of the laser tolerances that guarantee a given level of target performance.展开更多
On behalf of all at High Power Laser Science and Engineering we would like to congratulate the team at Lawrence Livermore National Laboratory(LLNL)on demonstrating fusion ignition at the National Ignition Facility.Thi...On behalf of all at High Power Laser Science and Engineering we would like to congratulate the team at Lawrence Livermore National Laboratory(LLNL)on demonstrating fusion ignition at the National Ignition Facility.This major scientific achievement was realized on the 5 December 2022 at the LLNL and announced at a press briefing on the 13 December 2022 by the United States Department of Energy’s National Nuclear Security Administration.This was a historic milestone and the culmination of decades of effort.展开更多
The recent achievement of fusion ignition with laser-driven technologies at the National Ignition Facility sets a historic accomplishment in fusion energy research.This accomplishment paves the way for using laser ine...The recent achievement of fusion ignition with laser-driven technologies at the National Ignition Facility sets a historic accomplishment in fusion energy research.This accomplishment paves the way for using laser inertial fusion as a viable approach for future energy production.Europe has a unique opportunity to empower research in this field internationally,and the scientific community is eager to engage in this journey.We propose establishing a European programme on inertial-fusion energy with the mission to demonstrate laser-driven ignition in the direct-drive scheme and to develop pathway technologies for the commercial fusion reactor.The proposed roadmap is based on four complementary axes:(ⅰ)the physics of laser-plasma interaction and burning plasmas;(ⅱ)high-energy high repetition rate laser technology;(ⅲ)fusion reactor technology and materials;and(ⅳ)reinforcement of the laser fusion community by international education and training programmes.We foresee collaboration with universities,research centres and industry and establishing joint activities with the private sector involved in laser fusion.This project aims to stimulate a broad range of high-profile industrial developments in laser,plasma and radiation technologies along with the expected high-level socio-economic impact.展开更多
The use of ultra-high intensity laser beams to achieve extreme material states in the laboratory has become almost routine with the development of the petawatt laser. Petawatt class lasers have been constructed for sp...The use of ultra-high intensity laser beams to achieve extreme material states in the laboratory has become almost routine with the development of the petawatt laser. Petawatt class lasers have been constructed for specific research activities,including particle acceleration, inertial confinement fusion and radiation therapy, and for secondary source generation(x-rays, electrons, protons, neutrons and ions). They are also now routinely coupled, and synchronized, to other large scale facilities including megajoule scale lasers, ion and electron accelerators, x-ray sources and z-pinches. The authors of this paper have tried to compile a comprehensive overview of the current status of petawatt class lasers worldwide.The definition of ‘petawatt class' in this context is a laser that delivers >200 TW.展开更多
As our understanding of the environmental impact of fossil fuel based energy production increases, it is becoming clear that the world needs a new energy solution to meet the challenges of the future. A transformation...As our understanding of the environmental impact of fossil fuel based energy production increases, it is becoming clear that the world needs a new energy solution to meet the challenges of the future. A transformation is required in the energy market to meet the need for low carbon, sustainable, affordable generation matched with security of supply. In the short term, an increasing contribution from renewable sources may provide a solution in some locations. In the longer term,low carbon, sustainable solutions must be developed to meet base load energy demand, if the world is to avoid an ever increasing energy gap and the attendant political instabilities. Laser-driven inertial fusion energy(IFE) may offer such a solution.展开更多
The Atomic Weapons Establishment(AWE) is tasked with supporting Continuous At Sea Deterrence(CASD) by certifying the performance and safety of the national deterrent in the Comprehensive Test Ban Treaty(CTBT) era. Thi...The Atomic Weapons Establishment(AWE) is tasked with supporting Continuous At Sea Deterrence(CASD) by certifying the performance and safety of the national deterrent in the Comprehensive Test Ban Treaty(CTBT) era. This means that recourse to further underground testing is not possible, and certification must be achieved by supplementing the historical data with the use of computer calculation. In order to facilitate this, AWE operates some of the largest supercomputers in the UK. To validate the computer codes, and indeed the designers who are using them, it is necessary to carry out further experiments in the right regimes. An excellent way to meet many of the requirements for material property data and to provide confidence in the validity of the algorithms is through experiments carried out on high power laser facilities.展开更多
The use of the Laser MegaJoule facility within the shock ignition scheme has been considered. In the first part of the study, one-dimensional hydrodynamic calculations were performed for an inertial confinement fusion...The use of the Laser MegaJoule facility within the shock ignition scheme has been considered. In the first part of the study, one-dimensional hydrodynamic calculations were performed for an inertial confinement fusion capsule in the context of the shock ignition scheme providing the energy gain and an estimation of the increase of the peak power due to the reduction of the photon penetration expected during the high-intensity spike pulse. In the second part, we considered a Laser MegaJoule configuration consisting of 176 laser beams that have been grouped providing two different irradiation schemes. In this configuration the maximum available energy and power are 1.3 MJ and 440 TW. Optimization of the laser–capsule parameters that minimize the irradiation non-uniformity during the first few ns of the foot pulse has been performed. The calculations take into account the specific elliptical laser intensity profile provided at the Laser MegaJoule and the expected beam uncertainties. A significant improvement of the illumination uniformity provided by the polar direct drive technique has been demonstrated. Three-dimensional hydrodynamic calculations have been performed in order to analyse the magnitude of the azimuthal component of the irradiation that is neglected in twodimensional hydrodynamic simulations.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
Supersonic flows with high Mach number are ubiquitous in astrophysics. High-powered lasers also have the ability to drive high Mach number, radiating shock waves in laboratory plasmas, and recent experiments along the...Supersonic flows with high Mach number are ubiquitous in astrophysics. High-powered lasers also have the ability to drive high Mach number, radiating shock waves in laboratory plasmas, and recent experiments along these lines have made it possible to recreate analogs of high Mach-number astrophysical flows under controlled conditions. Streak cameras such as the Rochester optical streak system(ROSS) are particularly helpful in diagnosing such experiments,because they acquire spatially resolved measurements of the radiating gas continuously over a large time interval,making it easy to observe how any shock waves and ablation fronts present in the system evolve with time. This paper summarizes new ROSS observations of a laboratory analog of the collision of a stellar wind with an ablating planetary atmosphere embedded within a magnetosphere. We find good agreement between the observed ROSS data and numerical models obtained with the FLASH code, but only when the effects of optical depth are properly taken into account.展开更多
A numerical method providing the optimal laser intensity profiles for a direct-drive inertial confinement fusion scheme has been developed. The method provides an alternative approach to phase-space optimization studi...A numerical method providing the optimal laser intensity profiles for a direct-drive inertial confinement fusion scheme has been developed. The method provides an alternative approach to phase-space optimization studies, which can prove computationally expensive. The method applies to a generic irradiation configuration characterized by an arbitrary number NBof laser beams provided that they irradiate the whole target surface, and thus goes beyond previous analyses limited to symmetric configurations. The calculated laser intensity profiles optimize the illumination of a spherical target.This paper focuses on description of the method, which uses two steps: first, the target irradiation is calculated for initial trial laser intensities, and then in a second step the optimal laser intensities are obtained by correcting the trial intensities using the calculated illumination. A limited number of example applications to direct drive on the Laser Mega Joule(LMJ) are described.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 on the design and first results from experiments looking at the formation of radiative shocks on the ShenguangII(SG-II)laser at the Shanghai Institute of Optics and Fine Mechanics in China.Laser-heating of a...We report on the design and first results from experiments looking at the formation of radiative shocks on the ShenguangII(SG-II)laser at the Shanghai Institute of Optics and Fine Mechanics in China.Laser-heating of a two-layer CH/CH–Br foil drives a∼40 km/s shock inside a gas cell filled with argon at an initial pressure of 1 bar.The use of gas-cell targets with large(several millimetres)lateral and axial extent allows the shock to propagate freely without any wall interactions,and permits a large field of view to image single and colliding counter-propagating shocks with time-resolved,pointprojection X-ray backlighting(∼20µm source size,4.3 keV photon energy).Single shocks were imaged up to 100 ns after the onset of the laser drive,allowing to probe the growth of spatial nonuniformities in the shock apex.These results are compared with experiments looking at counter-propagating shocks,showing a symmetric drive that leads to a collision and stagnation from∼40 ns onward.We present a preliminary comparison with numerical simulations with the radiation hydrodynamics code ARWEN,which provides expected plasma parameters for the design of future experiments in this facility.展开更多
Laser target components consist of multicomponent porous and nonporous materials that are adhesively bonded together.In order to assess the extent and quantity of adhesive wicking into porous foam, micro X-ray compute...Laser target components consist of multicomponent porous and nonporous materials that are adhesively bonded together.In order to assess the extent and quantity of adhesive wicking into porous foam, micro X-ray computed tomography(CT)and image processing software have been utilized. Two different laser target configurations have been assessed in situ and volume rendered images of the distribution and quantities of adhesive have been determined for each.展开更多
The Orion facility at the Atomic Weapons Establishment in the United Kingdom has the capability to operate one of its two 500 J, 500 fs short-pulse petawatt beams at the second harmonic, the principal reason being to ...The Orion facility at the Atomic Weapons Establishment in the United Kingdom has the capability to operate one of its two 500 J, 500 fs short-pulse petawatt beams at the second harmonic, the principal reason being to increase the temporal contrast of the pulse on target. This is achieved post-compression, using 3 mm thick type-1 potassium dihydrogen phosphate crystals. Since the beam diameter of the compressed pulse is ~600 mm, it is impractical to achieve this over the full aperture due to the unavailability of the large aperture crystals. Frequency doubling was originally achieved on Orion using a circular sub-aperture of 300 mm diameter. The reduction in aperture limited the output energy to 100 J.The second-harmonic capability has been upgraded by taking two square 300 mm × 300 mm sub-apertures from the beam and combining them at focus using a single paraboloidal mirror, thus creating a 200 J, 500 fs, i.e., 400 TW facility at the second harmonic.展开更多
The Orion laser facility at AWE provides multiple beams to target delivering synchronized pulses at both nanosecond and sub-picosecond duration.In the latter,the peak power approaches the petawatt level.This paper pre...The Orion laser facility at AWE provides multiple beams to target delivering synchronized pulses at both nanosecond and sub-picosecond duration.In the latter,the peak power approaches the petawatt level.This paper presents a conceptual design for potential development of these beamlines.This would deliver a significant enhancement of performance at the fundamental level.In addition,a new approach is described for the management of frequency conversion at high intensity,which may allow significantly enhanced performance at the second harmonic also.展开更多
In 2018 the journal High Power Laser Science and Engineering produced a Special Issue on Laboratory Astrophysics.The scope of the special issue was to span the latest research and reviews on the following topics relat...In 2018 the journal High Power Laser Science and Engineering produced a Special Issue on Laboratory Astrophysics.The scope of the special issue was to span the latest research and reviews on the following topics related to laboratory astrophysics and related phenomena.The topics invited for inclusion were:·collisionless shocks;·planetary formation dynamics and planetary interiors;·warm dense matter;·hydrodynamic and magnetohydrodynamic instabilities;·magnetic reconnection;·relativistic plasmas;·magnetic turbulence and magnetic amplification;·nuclear astrophysics;·radiative transfer and radiation hydrodynamics;·target design;·laser-based HED facilities.although this was not meant as an exhaustive list.As is usual with a special issue of this type Guest Editors were invited to lead in sourcing articles.展开更多
Fusion energy research is delivering impressive new results emerging from different infrastructures and industrial devices evolving rapidly from ideas to proof-of-principle demonstration and aiming at the conceptual d...Fusion energy research is delivering impressive new results emerging from different infrastructures and industrial devices evolving rapidly from ideas to proof-of-principle demonstration and aiming at the conceptual design of reactors for the production of electricity.A major milestone has recently been announced in laser fusion by the Lawrence Livermore National Laboratory and is giving new thrust to laser-fusion energy research worldwide.Here we discuss how these circumstances strongly suggest the need for a European intermediate-energy facility dedicated to the physics and technology of laser-fusion ignition,the physics of fusion materials and advanced technologies for high-repetitionrate,high-average-power broadband lasers.We believe that the participation of the broader scientific community and the increased engagement of industry,in partnership with research and academic institutions,make most timely the construction of this infrastructure of extreme scientific attractiveness.展开更多
Aerogel materials manufactured from metal oxides have been used as components in numerous high-energy density physics targets. These aerogels have been identified to be used as a future target material in the AWE fiel...Aerogel materials manufactured from metal oxides have been used as components in numerous high-energy density physics targets. These aerogels have been identified to be used as a future target material in the AWE fielded campaigns at the US National Ignition Facility. A wide variety of metal oxide aerogels are required for future campaigns and therefore a versatile manufacturing route is sought; as such, an epoxide-assisted sol–gel route was investigated. Under the European Union Registration, Evaluation, Authorization and Restriction of Chemicals legislation, the most commonly used epoxide, propylene oxide, is recognized as a substance of very high concern(SVHC). This work sought to investigate suitable alternative epoxides for use in target manufacture. The outcome was the identification of synthesis routes for stable metal oxide aerogel monoliths using epoxides not subject to the above restrictions.展开更多
基金sponsored by the NWIPT Department of the U.K.Ministry of Defence
文摘It has been said that,once a bomb casing has fractured, "detonation gases will then stream around the fragments or bypass them,and the acceleration process stops there." However,while apparently copious gas flow through casing fractures indicates some pressure release,it is also an indication of significant gas drive pressure,post casing fracture.This paper shows two approaches to the problem of calculating the actual loss of drive.One presents first-order analytical calculations,in cylindrical geometry,of pressure loss to the inside surface of a fractured casing.The second shows the modelling of a selected example in the CTH code.Both approaches reveal that gas escape,while occurring at its own soundspeed relative to the adjacent casing fragments,has to compete with rapid radial expansion of the casing.Together with some historic experiments now publicly available,our calculations indicate that post-fracture casing fragment acceleration is,for most systems,unlikely to be reduced significantly.
基金The research of R.R.was supported by the Spanish Ministerio de Econom´ıa y Competitividad,Project No.ENE2014-54960-R and by the EUROfusion Consortium under Project No.AWP15-ENR-01/CEA-02.M.T.is supported by CEA-ENS LRC-MESO Grant No.2018-011.
文摘Three-dimensional(3D)hydrodynamic numerical simulations of laser driven thin-shell gas-filled microballoons have been carried out using the computer code MULTI-3D[Ramis et al.,Phys.Plasmas 21,082710(2014)].The studied configuration corresponds to experiments carried at the ORION laser facility[Hopps et al.,Plasma Phys.Controlled Fusion 57,064002(2015)].The MULTI-3D code solves single-temperature hydrodynamics,electron heat transport,and 3D ray tracing with inverse bremsstrahlung absorption on unstructured Lagrangian grids.Special emphasis has been placed on the genuine 3D effects that are inaccessible to calculations using simplified 1D or 2D geometries.These include the consequences of(i)a finite number of laser beams(10 in the experimental campaign),(ii)intensity irregularities in the beam crosssectional profiles,(iii)laser beam misalignments,and(iv)power imbalance between beams.The consequences of these imperfections have been quantified by post-processing the numerical results in terms of capsule nonuniformities(synthetic emission and absorption images)and implosion efficiency(convergence ratio and neutron yield).Statistical analysis of these outcomes allows determination of the laser tolerances that guarantee a given level of target performance.
文摘On behalf of all at High Power Laser Science and Engineering we would like to congratulate the team at Lawrence Livermore National Laboratory(LLNL)on demonstrating fusion ignition at the National Ignition Facility.This major scientific achievement was realized on the 5 December 2022 at the LLNL and announced at a press briefing on the 13 December 2022 by the United States Department of Energy’s National Nuclear Security Administration.This was a historic milestone and the culmination of decades of effort.
文摘The recent achievement of fusion ignition with laser-driven technologies at the National Ignition Facility sets a historic accomplishment in fusion energy research.This accomplishment paves the way for using laser inertial fusion as a viable approach for future energy production.Europe has a unique opportunity to empower research in this field internationally,and the scientific community is eager to engage in this journey.We propose establishing a European programme on inertial-fusion energy with the mission to demonstrate laser-driven ignition in the direct-drive scheme and to develop pathway technologies for the commercial fusion reactor.The proposed roadmap is based on four complementary axes:(ⅰ)the physics of laser-plasma interaction and burning plasmas;(ⅱ)high-energy high repetition rate laser technology;(ⅲ)fusion reactor technology and materials;and(ⅳ)reinforcement of the laser fusion community by international education and training programmes.We foresee collaboration with universities,research centres and industry and establishing joint activities with the private sector involved in laser fusion.This project aims to stimulate a broad range of high-profile industrial developments in laser,plasma and radiation technologies along with the expected high-level socio-economic impact.
文摘The use of ultra-high intensity laser beams to achieve extreme material states in the laboratory has become almost routine with the development of the petawatt laser. Petawatt class lasers have been constructed for specific research activities,including particle acceleration, inertial confinement fusion and radiation therapy, and for secondary source generation(x-rays, electrons, protons, neutrons and ions). They are also now routinely coupled, and synchronized, to other large scale facilities including megajoule scale lasers, ion and electron accelerators, x-ray sources and z-pinches. The authors of this paper have tried to compile a comprehensive overview of the current status of petawatt class lasers worldwide.The definition of ‘petawatt class' in this context is a laser that delivers >200 TW.
基金The HiPER Preparatory Phase Project was supported by FP7-Infrastructures-2007-1 (Grant Agreement number 211737): ‘The European High Power laser Energy Research facility Preparatory Phase Study’the UK Science, Technology and Facilities Council the Ministry of Education, Youth and Sports of the Czech Republic and many ‘in-kind contributions’ from the HiPER partners and their sponsoring agencies
文摘As our understanding of the environmental impact of fossil fuel based energy production increases, it is becoming clear that the world needs a new energy solution to meet the challenges of the future. A transformation is required in the energy market to meet the need for low carbon, sustainable, affordable generation matched with security of supply. In the short term, an increasing contribution from renewable sources may provide a solution in some locations. In the longer term,low carbon, sustainable solutions must be developed to meet base load energy demand, if the world is to avoid an ever increasing energy gap and the attendant political instabilities. Laser-driven inertial fusion energy(IFE) may offer such a solution.
文摘The Atomic Weapons Establishment(AWE) is tasked with supporting Continuous At Sea Deterrence(CASD) by certifying the performance and safety of the national deterrent in the Comprehensive Test Ban Treaty(CTBT) era. This means that recourse to further underground testing is not possible, and certification must be achieved by supplementing the historical data with the use of computer calculation. In order to facilitate this, AWE operates some of the largest supercomputers in the UK. To validate the computer codes, and indeed the designers who are using them, it is necessary to carry out further experiments in the right regimes. An excellent way to meet many of the requirements for material property data and to provide confidence in the validity of the algorithms is through experiments carried out on high power laser facilities.
基金the support given to this work. R. R. was partially supported by the EURATOM/CIEMAT association in the framework of the ‘IFE Keep-in-Touch Activities’. S. W.acknowledges support from the Czech Science Foundation (Project No. CZ.1.07/2.3.00/20.0279) and from ELI (Project No. CZ.1.05/1.1.00/02.0061)
文摘The use of the Laser MegaJoule facility within the shock ignition scheme has been considered. In the first part of the study, one-dimensional hydrodynamic calculations were performed for an inertial confinement fusion capsule in the context of the shock ignition scheme providing the energy gain and an estimation of the increase of the peak power due to the reduction of the photon penetration expected during the high-intensity spike pulse. In the second part, we considered a Laser MegaJoule configuration consisting of 176 laser beams that have been grouped providing two different irradiation schemes. In this configuration the maximum available energy and power are 1.3 MJ and 440 TW. Optimization of the laser–capsule parameters that minimize the irradiation non-uniformity during the first few ns of the foot pulse has been performed. The calculations take into account the specific elliptical laser intensity profile provided at the Laser MegaJoule and the expected beam uncertainties. A significant improvement of the illumination uniformity provided by the polar direct drive technique has been demonstrated. Three-dimensional hydrodynamic calculations have been performed in order to analyse the magnitude of the azimuthal component of the irradiation that is neglected in twodimensional hydrodynamic simulations.
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the DOE NLUF program DE-FOA-0001568the Data Analysis and Visualization Cyber Infrastructure program OCI-0959097
文摘Supersonic flows with high Mach number are ubiquitous in astrophysics. High-powered lasers also have the ability to drive high Mach number, radiating shock waves in laboratory plasmas, and recent experiments along these lines have made it possible to recreate analogs of high Mach-number astrophysical flows under controlled conditions. Streak cameras such as the Rochester optical streak system(ROSS) are particularly helpful in diagnosing such experiments,because they acquire spatially resolved measurements of the radiating gas continuously over a large time interval,making it easy to observe how any shock waves and ablation fronts present in the system evolve with time. This paper summarizes new ROSS observations of a laboratory analog of the collision of a stellar wind with an ablating planetary atmosphere embedded within a magnetosphere. We find good agreement between the observed ROSS data and numerical models obtained with the FLASH code, but only when the effects of optical depth are properly taken into account.
基金partially supported by the EURATOM/CIEMAT association in the framework of the ‘IFE Keep-in-Touch Activities’
文摘A numerical method providing the optimal laser intensity profiles for a direct-drive inertial confinement fusion scheme has been developed. The method provides an alternative approach to phase-space optimization studies, which can prove computationally expensive. The method applies to a generic irradiation configuration characterized by an arbitrary number NBof laser beams provided that they irradiate the whole target surface, and thus goes beyond previous analyses limited to symmetric configurations. The calculated laser intensity profiles optimize the illumination of a spherical target.This paper focuses on description of the method, which uses two steps: first, the target irradiation is calculated for initial trial laser intensities, and then in a second step the optimal laser intensities are obtained by correcting the trial intensities using the calculated illumination. A limited number of example applications to direct drive on the Laser Mega Joule(LMJ) are described.
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the Royal Society(UK)through a University Research Fellowship(URF-R-180032)a Research Fellows Enhancement Award(RGF-EA-180240)+2 种基金an International Exchanges grant(IES-R3-170140)a Research Grant(RG2017-R2)The authors would like to thank the operation group of the SG-II laser facility.C.S.acknowledges support from the French INSU-PNPS programme.U.C.acknowledges support by the project Advanced Research(CZ.02.1.01/0.0/0.0/16_019/0000789)from European Regional Development Fund(ADONIS)。
文摘We report on the design and first results from experiments looking at the formation of radiative shocks on the ShenguangII(SG-II)laser at the Shanghai Institute of Optics and Fine Mechanics in China.Laser-heating of a two-layer CH/CH–Br foil drives a∼40 km/s shock inside a gas cell filled with argon at an initial pressure of 1 bar.The use of gas-cell targets with large(several millimetres)lateral and axial extent allows the shock to propagate freely without any wall interactions,and permits a large field of view to image single and colliding counter-propagating shocks with time-resolved,pointprojection X-ray backlighting(∼20µm source size,4.3 keV photon energy).Single shocks were imaged up to 100 ns after the onset of the laser drive,allowing to probe the growth of spatial nonuniformities in the shock apex.These results are compared with experiments looking at counter-propagating shocks,showing a symmetric drive that leads to a collision and stagnation from∼40 ns onward.We present a preliminary comparison with numerical simulations with the radiation hydrodynamics code ARWEN,which provides expected plasma parameters for the design of future experiments in this facility.
文摘Laser target components consist of multicomponent porous and nonporous materials that are adhesively bonded together.In order to assess the extent and quantity of adhesive wicking into porous foam, micro X-ray computed tomography(CT)and image processing software have been utilized. Two different laser target configurations have been assessed in situ and volume rendered images of the distribution and quantities of adhesive have been determined for each.
文摘The Orion facility at the Atomic Weapons Establishment in the United Kingdom has the capability to operate one of its two 500 J, 500 fs short-pulse petawatt beams at the second harmonic, the principal reason being to increase the temporal contrast of the pulse on target. This is achieved post-compression, using 3 mm thick type-1 potassium dihydrogen phosphate crystals. Since the beam diameter of the compressed pulse is ~600 mm, it is impractical to achieve this over the full aperture due to the unavailability of the large aperture crystals. Frequency doubling was originally achieved on Orion using a circular sub-aperture of 300 mm diameter. The reduction in aperture limited the output energy to 100 J.The second-harmonic capability has been upgraded by taking two square 300 mm × 300 mm sub-apertures from the beam and combining them at focus using a single paraboloidal mirror, thus creating a 200 J, 500 fs, i.e., 400 TW facility at the second harmonic.
文摘The Orion laser facility at AWE provides multiple beams to target delivering synchronized pulses at both nanosecond and sub-picosecond duration.In the latter,the peak power approaches the petawatt level.This paper presents a conceptual design for potential development of these beamlines.This would deliver a significant enhancement of performance at the fundamental level.In addition,a new approach is described for the management of frequency conversion at high intensity,which may allow significantly enhanced performance at the second harmonic also.
文摘In 2018 the journal High Power Laser Science and Engineering produced a Special Issue on Laboratory Astrophysics.The scope of the special issue was to span the latest research and reviews on the following topics related to laboratory astrophysics and related phenomena.The topics invited for inclusion were:·collisionless shocks;·planetary formation dynamics and planetary interiors;·warm dense matter;·hydrodynamic and magnetohydrodynamic instabilities;·magnetic reconnection;·relativistic plasmas;·magnetic turbulence and magnetic amplification;·nuclear astrophysics;·radiative transfer and radiation hydrodynamics;·target design;·laser-based HED facilities.although this was not meant as an exhaustive list.As is usual with a special issue of this type Guest Editors were invited to lead in sourcing articles.
文摘Fusion energy research is delivering impressive new results emerging from different infrastructures and industrial devices evolving rapidly from ideas to proof-of-principle demonstration and aiming at the conceptual design of reactors for the production of electricity.A major milestone has recently been announced in laser fusion by the Lawrence Livermore National Laboratory and is giving new thrust to laser-fusion energy research worldwide.Here we discuss how these circumstances strongly suggest the need for a European intermediate-energy facility dedicated to the physics and technology of laser-fusion ignition,the physics of fusion materials and advanced technologies for high-repetitionrate,high-average-power broadband lasers.We believe that the participation of the broader scientific community and the increased engagement of industry,in partnership with research and academic institutions,make most timely the construction of this infrastructure of extreme scientific attractiveness.
基金funded by AWE,Aldermaston,Reading,Berkshire,RG7 4PR,UK
文摘Aerogel materials manufactured from metal oxides have been used as components in numerous high-energy density physics targets. These aerogels have been identified to be used as a future target material in the AWE fielded campaigns at the US National Ignition Facility. A wide variety of metal oxide aerogels are required for future campaigns and therefore a versatile manufacturing route is sought; as such, an epoxide-assisted sol–gel route was investigated. Under the European Union Registration, Evaluation, Authorization and Restriction of Chemicals legislation, the most commonly used epoxide, propylene oxide, is recognized as a substance of very high concern(SVHC). This work sought to investigate suitable alternative epoxides for use in target manufacture. The outcome was the identification of synthesis routes for stable metal oxide aerogel monoliths using epoxides not subject to the above restrictions.