Obtaining inertial fusion energy requires higher gain in laser indirect drive inertial confinement fusion(ICF),but traditional cylindrical hohlraums face two persistent challenges:low energy coupling efficiency from t...Obtaining inertial fusion energy requires higher gain in laser indirect drive inertial confinement fusion(ICF),but traditional cylindrical hohlraums face two persistent challenges:low energy coupling efficiency from the hohlraum to the capsule and severe inner beam interception by outer gold bubbles,both needing optimization for improved ICF performance.In this paper,a new domed-rugby hohlraum design is proposed.The novel and optimized hohlraum configuration increases the energy coupling efficiency by reducing the wall surface and energy loss with a rugby-shaped geometry,thereby enhancing the radiation source temperature.Simultaneously,through a special toroidal dome structure,the interaction between the outer bubble plasma and inner laser beams is mitigated,allowing the inner laser beams to reach the waist of the hohlraum.As a result,more spherical implosions are obtained and the quality of the radiation source is improved.It has been simulated that on the 100 kJ class laser facility,there is a 20%higher neutron yield.The integrated implosion performance is expected to be significantly advanced in such a novel configuration,providing a new concept for hohlraum configuration designs with a high-temperature and high-quality radiation source.展开更多
Computational simulations on structurally different detonation generator are carried out to study the phenomena,the mechanism and the gas dynamics characteristics of flame implosion and shock wave focusing.Two-dimensi...Computational simulations on structurally different detonation generator are carried out to study the phenomena,the mechanism and the gas dynamics characteristics of flame implosion and shock wave focusing.Two-dimensional axisymmetric and unsteady Navier-Stokes equations are numerically solved and detailed chemical reaction kinetics of hydrogen/air mixture is used.The simulation results show that the laminar flame generated by low energy spark in the jet flame burner is accelerated under the narrow channel,the jet flame impinging on the axis strengthens shock wave and the shock wave enhances flame acceleration.Under the function of multiple shock waves and flame,a number of hot spots appear between the wave and the surface.The spots enlarge rapidly,thus forming an over-drive detonation with high pressure,and then declining to stable detonation.Through calculation and analysis,the length of detonation initiation and stable detonation are obtained,thus providing the useful information for further experimental investigations.展开更多
-By using gas-liquid two-phase flow theory, a modified mathematical model based on the computational fluid dynamics method SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) is introduced to investigate implo...-By using gas-liquid two-phase flow theory, a modified mathematical model based on the computational fluid dynamics method SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) is introduced to investigate implosion phenomena in high pressure chambers systematically. A theoretical simulation-prediction method, which is independent of experimental data, is developed in the paper and great improvement has been made on the topic. In the paper, various implosion situations have been simulated and predicted. Effects of a series of factors influencing implosion results and methods of reducing implosion danger have been analysed. The analysis results are of importance to underwater engineering practice.展开更多
A Lagrangian compatible radiation hydrodynamic algorithm and the nuclear dynamics computing module are developed and implemented in the LARED Integration code, which is a radiation hydrodynamic code based on the 2-D c...A Lagrangian compatible radiation hydrodynamic algorithm and the nuclear dynamics computing module are developed and implemented in the LARED Integration code, which is a radiation hydrodynamic code based on the 2-D cylindrical coordinates for the numerical simulation of the indirect-drive Inertial Confined Fusion. A number of 1-D and 2-D ignition implosion numerical simulations by using the improved LARED Integration code (ILARED) are presented which show that the 1-D numerical results are consistent with those computed by the 1-D radiation hydrodynamic code RDMG, while the simulation results of the 2-D low-mode radiative asymmetry and hydrodynamic instability growth,according to the physical analysis and anticipation, are satisfactory. The capsules driven by the sources from SGII experiments are also simulated by ILARED, and the fuel shapes agree well with the experimental results. The numerical simulations demonstrate that ILARED can be used in the simulation of the 1-D and 2-D ignition capsule implosion using the multi-group diffusion model for radiation.展开更多
The thin aluminum liners with an aspect ratio R/?r 1 have been imploded on the primary test stand(PTS) facility,where R is the outer radius of the liner and ?r is the thickness. The x-ray self-emission images present ...The thin aluminum liners with an aspect ratio R/?r 1 have been imploded on the primary test stand(PTS) facility,where R is the outer radius of the liner and ?r is the thickness. The x-ray self-emission images present azimuthally correlated perturbations in the liner implosions. The experiments show that at-10 ns before the stagnation, the wavelengths of perturbation are about 0.93 mm and 1.67 mm for the small-radius and large-radius liners, respectively. We have utilized the resistive magnetohydrodynamic code PLUTO to study the development of magneto-Rayleigh–Taylor(MRT) instabilities under experimental conditions. The calculated perturbation amplitudes are consistent with the experimental observations very well. We have found that both mode coupling and long implosion distance are responsible for the more developed instabilities in the large-radius liner implosions.展开更多
The low-mode shell asymmetry and high-mode hot spot mixing appear to be the main reasons for the performance degradation of the National Ignition Facility(NIF)implosion experiments.The effects of the mode coupling bet...The low-mode shell asymmetry and high-mode hot spot mixing appear to be the main reasons for the performance degradation of the National Ignition Facility(NIF)implosion experiments.The effects of the mode coupling between low-mode P2 radiation flux asymmetry and intermediate-mode L=24 capsule roughness on the implosion performance of ignition capsule are investigated by two-dimensional radiation hydrodynamic simulations.It is shown that the amplitudes of new modes generated by the mode coupling are in good agreement with the second-order mode coupling equation during the acceleration phase.The later flow field not only shows large areal density P2 asymmetry in the main fuel,but also generates large-amplitude spikes and bubbles.In the deceleration phase,the increasing mode coupling generates more new modes,and the perturbation spectrum on the hot spot boundary is mainly from the strong mode interactions rather than the initial perturbation conditions.The combination of the low-mode and high-mode perturbations breaks up the capsule shell,resulting in a significant reduction of the hot spot temperature and implosion performance.展开更多
Implosion asymmetry is a crucial problem quenching ignition in the field of inertial confinement fusion.A forward-calculation method based on 1D and 2D hydrodynamic simulations has been developed to generate and study...Implosion asymmetry is a crucial problem quenching ignition in the field of inertial confinement fusion.A forward-calculation method based on 1D and 2D hydrodynamic simulations has been developed to generate and study the x-ray images of hot-spot self-emission,indicating asymmetry integrated over the entire drive pulse.It is shown that the x-ray imaging photon energy should be higher to avoid the influence of the remaining shell.The contour level(percentage of the maximum emission intensity)and spatial resolution should be as low as possible,optimally less than 20%and 3μm,for characterization of higher-mode signatures such as Ps-P12 by x-ray self-emission images.On the contrary,signatures of lower-mode such as P2 remain clear at all contour levels and spatial resolutions.These key results can help determine the optimal diagnostics,laser,and target parameters for implosion experiments.Recent typical hot-spot asymmetry measurements and applications on the Shenguang 100 kJ class laser facility are also reported.展开更多
We investigated the radiation characteristics and implosion dynamics of low-wire-number cylindrical tungsten wire array Z-pinches on the YANG accelerator with a peak current 0.8-1.1 MA and a rising time ～ 90 ns.The a...We investigated the radiation characteristics and implosion dynamics of low-wire-number cylindrical tungsten wire array Z-pinches on the YANG accelerator with a peak current 0.8-1.1 MA and a rising time ～ 90 ns.The arrays are made up of（8-32）×5 μm wires 6/10 mm in diameter and 15 mm in height.The highest X-ray power obtained in the experiments was about 0.37 TW with the total radiation energy ～ 13 kJ and the energy conversion efficiency ～ 9%（24×5 μm wires,6 mm in diameter）.Most of the X-ray emissions from tungsten Z-pinch plasmas were distributed in the spectral band of 100-600 eV,peaked at 250 and 375 eV.The dominant wavelengths of the wire ablation and the magneto-Rayleigh-Taylor instability were found and analyzed through measuring the time-gated self-emission and laser interferometric images.Through analyzing the implosion trajectories obtained by an optical streak camera,the run-in velocities of the Z-pinch plasmas at the end of the implosion phase were determined to be about（1.3-2.1）×10 7 cm/s.展开更多
Purpose: The purpose of this study is to introduce a new concept and term into the scientometric discourse and research—scientometric implosion—and test the idea on the example of the Armenian journals. The article ...Purpose: The purpose of this study is to introduce a new concept and term into the scientometric discourse and research—scientometric implosion—and test the idea on the example of the Armenian journals. The article argues that the existence of a compressed scientific area in the country makes pressure on the journals and after some time this pressure makes one or several journals explode—break the limited national scientific area and move to the international arena. As soon as one of the local journals breaks through this compressed space and appears at an international level, further explosion happens, which makes the other journals follow the same path.Design/methodology/approach: Our research is based on three international scientific databases—WoS, Scopus, and RISC CC, from where we have retrieved information about the Armenian journals indexed there and citations received by those journals and one national database—the Armenian Science Citation Index. Armenian Journal Impact Factor(ArmJIF) was calculated for the local Armenian journals based on the general impact factor formula. Journals were classified according to Gl?nzel and Schubert(2003). Findings: Our results show that the science policy developed by the scientific authorities of Armenia and the introduction of ArmJIF have made the Armenian journals comply with international standards and resulted in some local journals to break the national scientific territory and be indexed in international scientific databases of RISC, Scopus, and WoS. Apart from complying with technical requirements, the journals start publishing articles also in foreign languages. Although nearly half of the local journals are in the fields of social sciences and humanities, only one journal from that field is indexed in international scientific databases. Research limitation: One of the limitations of the study is that it was performed on the example of only one state and the second one is that more time passage is needed to firmly evaluate the results. However, the introduction of the concept can inspire other similar case study. Practical implications: The new term and relevant model offered in the article can practically be used for the development of national journals.Originality/value: The article proposes a new term and a concept in scientometrics.展开更多
A magnetohydrodynamic (MHD) formulation is derived to investigate and compare the mitigation effects of both the sheared axial flow and finite Larmor radius (FLR) on the Rayleigh-Taylor (RT) instability in Z-pinch imp...A magnetohydrodynamic (MHD) formulation is derived to investigate and compare the mitigation effects of both the sheared axial flow and finite Larmor radius (FLR) on the Rayleigh-Taylor (RT) instability in Z-pinch implosions. The sheared axial flow is introduced into MHD equations in a conventional way and the FLR effect into the equations via /t → -i(w+ik⊥2pi2Ωi,), as proposed in our previous paper [Chin. Phys. Lett. 2002, 19:217] , where k⊥2 pi2 is referred to FLR effect from the general kinetic theory of magnetized plasma. Therefore the linearized continuity and momentum equations for the perturbed mass-density and velocity include both the sheared axial flow and the FLR effect. It is found that the effect of sheared axial flow with a lower peak velocity can mitigate RT instability in the whole wavenumber region and the effect of sheared axial flow with a higher one can mitigate RT instability only in the large wavenumber region (for normalized wavenumber k】2.4); The effect of FLR can mitigate RT instability in the whole wavenumber region and the mitigation effect is stronger than that of the sheared axial flow with a lower peak velocity in the almost whole wavenumber region.展开更多
The neutron Doppler broadening in inertial confinement fusion has been acquired from the time of flight for the neutron, from which the fuel ion temperature can be derived. An ultrafast-quenched plastic scintillation ...The neutron Doppler broadening in inertial confinement fusion has been acquired from the time of flight for the neutron, from which the fuel ion temperature can be derived. An ultrafast-quenched plastic scintillation detector was used to measure the time of flight for the neutron at a low-imploded DT neutron yield (5×107-1×108) in the experiment performed on the Shenguang Ⅱ laser facility. The typical temperatures of ablating targets for indirect drive were around 2.8 keV and the uncertainties were ±30 % - ±40%. The detection efficiency of the detector for DT neutrons was calibrated at a K-400 accelerator. The time response function of the detection system was calibrated by imploded neutrons from a DT-filled capsule, which can be regarded as a S function pulsed neutron source due to its much narrower pulse width than that of the measured neutron time-of-flight spectrum.展开更多
This paper generalizes the single-shell Kidder＇s self-similar solution to the double-shell one with a discontinuity in density across the interface. An isentropic implosion model is constructed to study the Rayleigh-...This paper generalizes the single-shell Kidder＇s self-similar solution to the double-shell one with a discontinuity in density across the interface. An isentropic implosion model is constructed to study the Rayleigh-Taylor instability for the implosion compression. A Godunov-type method in the Lagrangian coordinates is used to compute the one-dimensional Euler equation with the initial and boundary conditions for the double-shell Kidder＇s self-similar solution in spherical geometry. Numerical results are obtained to validate the double-shell implosion model. By programming and using the linear perturbation codes, a linear stability analysis on the Rayleigh-Taylor instability for the double-shell isentropic implosion model is performed. It is found that, when the initial perturbation is concentrated much closer to the interface of the two shells, or when the spherical wave number becomes much smaller, the modal radius of the interface grows much faster, i.e., more unstable. In addition, from the spatial point of view for the compressibility effect on the perturbation evolution, the compressibility of the outer shell has a destabilization effect on the Rayleigh-Taylor instability, while the compressibility of the inner shell has a stabilization effect.展开更多
Chimney implosion is the strategic planning of explosives and accessories materials and timings of its detonation so that chimney collapses on itself, minimising the physical damage to its immediate surroundings. Buil...Chimney implosion is the strategic planning of explosives and accessories materials and timings of its detonation so that chimney collapses on itself, minimising the physical damage to its immediate surroundings. Built in 1885, the brick chimney at kankanee colliery, Sijua area, BCCL （Bharat Collieries Company Limited） was demolished by felling method using the commercial explosives by adopting single-folding and toppling method. The chimney was 31.5 m in height and suffered structural weaknesses due to progressive deterioration over age, weathering and non maintenance. The chimney was posing potential threat to the safety of the nearby dwellings and surface structures, viz. main mechanical ventilator of Kankanee colliery, 11 KV electrical substation supplying power to Sijua area, BCCL, high tension cable line and busy Katras-Sijua-Dhanbad Dobari Road all failing within a radius of 30 m. About 75.22 kg of commercial explosive, 100 m of detonating fuse along with 0 and 25 ms delay detonators were used for controlled demolition of chimney. The chimney got demolished by vertically cascading on its own base without causing any damage to the nearby dwellings and surface structures.展开更多
Due to sophistications in experimental studies,the implosions in chain reaction,also named as sympathetic implosions,demand numerical models to understand the phenomena caused by various impacts to the primary sphere....Due to sophistications in experimental studies,the implosions in chain reaction,also named as sympathetic implosions,demand numerical models to understand the phenomena caused by various impacts to the primary sphere.We developed a 3D air-solid-water model considering the influence of brittle sphere failures of two alumina spheres to simulate the outbreak of the sympathetic implosion in the seawater of 114 MPa.According to the triggering mode,two cases of simultaneous implosions and five cases of sympathetic implosions of a double-sphere were numerically studied.We found that the induced fracture of the secondary sphere happened before the outbreak of the positive pressure wave,i.e.,the induced fracture is caused by the uneven pressure around the sphere lower than the hydrostatic pressure.To our knowledge,the present paper is the first report on the early fracture of the secondary solid sphere in sympathetic implosions.With various triggering modes of the primary sphere,the secondary fractures are all induced at the proximal side and extend to the other side.The formed ring-shaped implosion cores are caused by individual fracture mode.The shifting of the two implosion cores eventually affects the pressure pulses at a position.A higher or similar values of the secondary pulse are found closely related to the double sphere’s fracture modes,i.e.,related to the triggering modes of the local impacts.This work help to estimate the damage of the sympathetic implosion to the surroundings,and prevent further implosions by understanding spatial superposition of a series of pulses.展开更多
The double-cone ignition scheme is a promising novel ignition method,which is expected to greatly save the driver energy and enhance the robustness of the implosion process.In this paper,ablation of the inner surface ...The double-cone ignition scheme is a promising novel ignition method,which is expected to greatly save the driver energy and enhance the robustness of the implosion process.In this paper,ablation of the inner surface of the cone by the hard X-ray from coronal Au plasma is studied via radiation hydrodynamics simulations.It is found that the X-ray ablation of the inner wall will form strong pre-plasma,which will significantly affect the implosion process and cause the Au plasma to mix with the fuel,leading to ignition failure.The radiation and pre-ablation intensities in the system are estimated,and the evolutions of areal density,ion temperature and the distribution of Au ions are analysed.In addition,the mixing of Au in CH at collision is quantified.Then,a scheme to reduce the X-ray pre-ablation by replacing the gold cone with a tungsten cone is proposed,showing that it is effective in reducing high-Z mixing and improving collision results.展开更多
The effect of drive laser wavelength on the growth of ablative Rayleigh–Taylor instability(ARTI)in inertial confinemen fusion(ICF)is studied with two-dimensional numerical simulations.The results show that in the pla...The effect of drive laser wavelength on the growth of ablative Rayleigh–Taylor instability(ARTI)in inertial confinemen fusion(ICF)is studied with two-dimensional numerical simulations.The results show that in the plasma acceleration phase,shorter wavelengths lead to more efficien coupling between the laser and the kinetic energy of the implosion fluid Under the condition that the laser energy coupled to the implosion flui is constant,the ARTI growth rate decreases as the laser wavelength moves toward the extreme ultraviolet band,reaching its minimum value near λ=65 nm,and when the laser wavelength continuously moves toward the X-ray band,the ARTI growth rate increases rapidly.It is found that the results deviate from the theoretical ARTI growth rate.As the laser intensity benchmark increases,the position of the minimum ARTI growth rate shifts toward shorter wavelengths.As the initial sinusoidal perturbation wavenumber decreases,the position of the minimum ARTI growth rate shifts toward longer wavelengths.We believe that the conclusions drawn from the present simulations and analysis will help provide a better understanding of the ICF process and improve the theory of ARTI growth.展开更多
Pressure hulls play an important role in deep-sea underwater vehicles.However,in the ultra-high pressure environment,a highly destructive phenomenon could occur to them which is called implosion.To study the character...Pressure hulls play an important role in deep-sea underwater vehicles.However,in the ultra-high pressure environment,a highly destructive phenomenon could occur to them which is called implosion.To study the characteristics of the flow field of the underwater implosion of hollow ceramic pressure hulls,the compressible multiphase flow theory,direct numerical simulation,and adaptive mesh refinement are used to numerically simulate the underwater implosion of a single ceramic pressure hull and multiple linearly arranged ceramic pressure hulls.Firstly,the feasibility of the numerical simulation method is verified.Then,the results of the flow field of the underwater implosion of hollow ceramic pressure hulls in 11000 m depth is analyzed.There are the compression-rebound processes of the internal air cavity in the implosion.In the rebound stage,a shock wave that is several times the ambient pressure is generated outside the pressure hull,and the propagation speed is close to the speed of sound.The pressure peak of the shock wave has a negative exponential power function relationship with the distance to the center of the sphere.Finally,it is found that the obvious superimposed effect between spheres exists in the chain-reaction implosion which enhances the implosion shock wave.展开更多
Inertial fusion energy （IFE） has been considered a promising, nearly inexhaustible source of sustainable carbon-free power for the world＇s energy future. It has long been recognized that the control of hydrodynamic...Inertial fusion energy （IFE） has been considered a promising, nearly inexhaustible source of sustainable carbon-free power for the world＇s energy future. It has long been recognized that the control of hydrodynamic instabilities is of critical importance for ignition and high-gain in the inertial-confinement fusion （ICF） hot-spot ignition scheme. In this mini-review, we summarize the progress of theoretical and simulation research of hydrodynamic instabilities in the ICF central hot-spot implosion in our group over the past decade. In order to obtain sufficient understanding of the growth of hydrodynamic instabilities in ICF, we first decompose the problem into different stages according to the implosion physics processes. The decomposed essential physics pro- cesses that are associated with ICF implosions, such as Rayleigh-Taylor instability （RTI）, Richtmyer-Meshkov instability （RMI）, Kelvin-Helmholtz instability （KHI）, convergent geometry effects, as well as perturbation feed-through are reviewed. Analyti- cal models in planar, cylindrical, and spherical geometries have been established to study different physical aspects, including density-gradient, interface-coupling, geometry, and convergent effects. The influence of ablation in the presence of preheating on the RTI has been extensively studied by numerical simulations. The KHI considering the ablation effect has been discussed in detail for the first time. A series of single-mode ablative RTI experiments has been performed on the Shenguang-II laser facility. The theoretical and simulation research provides us the physical insights of linear and weakly nonlinear growths, and nonlinear evolutions of the hydrodynamic instabilities in ICF implosions, which has directly supported the research of ICF ignition target design. The ICF hot-spot ignition implosion design that uses several controlling features, based on our current understanding of hydrodynamic instabilities, to address shell implosion stability, has been briefly described, several of which are novel.展开更多
Microtube implosions are a novel scheme to generate ultrahigh magnetic fields of the megatesla order.These implosions are driven by ultraintense and ultrashort laser pulses.Using two-and three-dimensional particle sim...Microtube implosions are a novel scheme to generate ultrahigh magnetic fields of the megatesla order.These implosions are driven by ultraintense and ultrashort laser pulses.Using two-and three-dimensional particle simulations where megatesla-order magnetic fields can be achieved,we demonstrate scaling and criteria in terms of laser parameters,such as laser intensity and laser energy,to facilitate practical experiments toward the realization of extreme physical conditions,which have yet to be realized in laboratories.Microtube implosions should provide a new platform for studies in fundamental and applied physics relevant to ultrahigh magnetic fields.展开更多
In this review paper on heavy ion inertial fusion(HIF),the state-of-the-art scientific results are presented and discussed on the HIF physics,including physics of the heavy ion beam(HIB)transport in a fusion reactor,t...In this review paper on heavy ion inertial fusion(HIF),the state-of-the-art scientific results are presented and discussed on the HIF physics,including physics of the heavy ion beam(HIB)transport in a fusion reactor,the HIBs-ion illumination on a direct-drive fuel target,the fuel target physics,the uniformity of the HIF target implosion,the smoothing mechanisms of the target implosion non-uniformity and the robust target implosion.The HIB has remarkable preferable features to release the fusion energy in inertial fusion:in particle accelerators HIBs are generated with a high driver efficiency of~30%-40%,and the HIB ions deposit their energy inside of materials.Therefore,a requirement for the fusion target energy gain is relatively low,that would be~50-70 to operate a HIF fusion reactor with the standard energy output of 1 GWof electricity.The HIF reactor operation frequency would be~10-15 Hz or so.Several-MJ HIBs illuminate a fusion fuel target,and the fuel target is imploded to about a thousand times of the solid density.Then the DT fuel is ignited and burned.The HIB ion deposition range is defined by the HIB ions stopping length,which would be~1 mm or so depending on the material.Therefore,a relatively large density-scale length appears in the fuel target material.One of the critical issues in inertial fusion would be a spherically uniform target compression,which would be degraded by a non-uniform implosion.The implosion non-uniformity would be introduced by the Rayleigh-Taylor(R-T)instability,and the large densitygradient-scale length helps to reduce the R-T growth rate.On the other hand,the large scale length of the HIB ions stopping range suggests that the temperature at the energy deposition layer in a HIF target does not reach a very-high temperature:normally about 300 eV or so is realized in the energy absorption region,and that a direct-drive target would be appropriate in HIF.In addition,the HIB accelerators are operated repetitively and stably.The precise control of the HIB axis manipulation is also realized in the HIF accelerator,and the HIB wobbling motion may give another tool to smooth the HIB illumination non-uniformity.The key issues in HIF physics are also discussed and presented in the paper.展开更多
基金supported by National Natural Science Foundation of China(Nos.12105269,12075218 and 12175210)。
文摘Obtaining inertial fusion energy requires higher gain in laser indirect drive inertial confinement fusion(ICF),but traditional cylindrical hohlraums face two persistent challenges:low energy coupling efficiency from the hohlraum to the capsule and severe inner beam interception by outer gold bubbles,both needing optimization for improved ICF performance.In this paper,a new domed-rugby hohlraum design is proposed.The novel and optimized hohlraum configuration increases the energy coupling efficiency by reducing the wall surface and energy loss with a rugby-shaped geometry,thereby enhancing the radiation source temperature.Simultaneously,through a special toroidal dome structure,the interaction between the outer bubble plasma and inner laser beams is mitigated,allowing the inner laser beams to reach the waist of the hohlraum.As a result,more spherical implosions are obtained and the quality of the radiation source is improved.It has been simulated that on the 100 kJ class laser facility,there is a 20%higher neutron yield.The integrated implosion performance is expected to be significantly advanced in such a novel configuration,providing a new concept for hohlraum configuration designs with a high-temperature and high-quality radiation source.
文摘Computational simulations on structurally different detonation generator are carried out to study the phenomena,the mechanism and the gas dynamics characteristics of flame implosion and shock wave focusing.Two-dimensional axisymmetric and unsteady Navier-Stokes equations are numerically solved and detailed chemical reaction kinetics of hydrogen/air mixture is used.The simulation results show that the laminar flame generated by low energy spark in the jet flame burner is accelerated under the narrow channel,the jet flame impinging on the axis strengthens shock wave and the shock wave enhances flame acceleration.Under the function of multiple shock waves and flame,a number of hot spots appear between the wave and the surface.The spots enlarge rapidly,thus forming an over-drive detonation with high pressure,and then declining to stable detonation.Through calculation and analysis,the length of detonation initiation and stable detonation are obtained,thus providing the useful information for further experimental investigations.
文摘-By using gas-liquid two-phase flow theory, a modified mathematical model based on the computational fluid dynamics method SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) is introduced to investigate implosion phenomena in high pressure chambers systematically. A theoretical simulation-prediction method, which is independent of experimental data, is developed in the paper and great improvement has been made on the topic. In the paper, various implosion situations have been simulated and predicted. Effects of a series of factors influencing implosion results and methods of reducing implosion danger have been analysed. The analysis results are of importance to underwater engineering practice.
基金Supported by the National Natural Science Foundation of China under Grant Nos.10901021,91130002,11126134and11105013the China Academy of Engineering Physics Project under Grant No.2012A0202010+1 种基金the National High Technology Research and Development Program of China under Grant No.2012AA01A303the National Hi-Tech Inertial Confinement Fusion Committee of China
文摘A Lagrangian compatible radiation hydrodynamic algorithm and the nuclear dynamics computing module are developed and implemented in the LARED Integration code, which is a radiation hydrodynamic code based on the 2-D cylindrical coordinates for the numerical simulation of the indirect-drive Inertial Confined Fusion. A number of 1-D and 2-D ignition implosion numerical simulations by using the improved LARED Integration code (ILARED) are presented which show that the 1-D numerical results are consistent with those computed by the 1-D radiation hydrodynamic code RDMG, while the simulation results of the 2-D low-mode radiative asymmetry and hydrodynamic instability growth,according to the physical analysis and anticipation, are satisfactory. The capsules driven by the sources from SGII experiments are also simulated by ILARED, and the fuel shapes agree well with the experimental results. The numerical simulations demonstrate that ILARED can be used in the simulation of the 1-D and 2-D ignition capsule implosion using the multi-group diffusion model for radiation.
基金supported by the National Natural Science Foundation of China(Grant Nos.11605013,11775032,11805019,and 11705013)
文摘The thin aluminum liners with an aspect ratio R/?r 1 have been imploded on the primary test stand(PTS) facility,where R is the outer radius of the liner and ?r is the thickness. The x-ray self-emission images present azimuthally correlated perturbations in the liner implosions. The experiments show that at-10 ns before the stagnation, the wavelengths of perturbation are about 0.93 mm and 1.67 mm for the small-radius and large-radius liners, respectively. We have utilized the resistive magnetohydrodynamic code PLUTO to study the development of magneto-Rayleigh–Taylor(MRT) instabilities under experimental conditions. The calculated perturbation amplitudes are consistent with the experimental observations very well. We have found that both mode coupling and long implosion distance are responsible for the more developed instabilities in the large-radius liner implosions.
基金This work is supported by the National Natural Science Foundation of China under Grant Nos.11575034,11275031,11401033,and 91330205.
文摘The low-mode shell asymmetry and high-mode hot spot mixing appear to be the main reasons for the performance degradation of the National Ignition Facility(NIF)implosion experiments.The effects of the mode coupling between low-mode P2 radiation flux asymmetry and intermediate-mode L=24 capsule roughness on the implosion performance of ignition capsule are investigated by two-dimensional radiation hydrodynamic simulations.It is shown that the amplitudes of new modes generated by the mode coupling are in good agreement with the second-order mode coupling equation during the acceleration phase.The later flow field not only shows large areal density P2 asymmetry in the main fuel,but also generates large-amplitude spikes and bubbles.In the deceleration phase,the increasing mode coupling generates more new modes,and the perturbation spectrum on the hot spot boundary is mainly from the strong mode interactions rather than the initial perturbation conditions.The combination of the low-mode and high-mode perturbations breaks up the capsule shell,resulting in a significant reduction of the hot spot temperature and implosion performance.
基金National Key R&D Program(No.2017YFA0403204)Laser Fusion Research Funds for Young Talents(No.RCFPD1-2017-1)。
文摘Implosion asymmetry is a crucial problem quenching ignition in the field of inertial confinement fusion.A forward-calculation method based on 1D and 2D hydrodynamic simulations has been developed to generate and study the x-ray images of hot-spot self-emission,indicating asymmetry integrated over the entire drive pulse.It is shown that the x-ray imaging photon energy should be higher to avoid the influence of the remaining shell.The contour level(percentage of the maximum emission intensity)and spatial resolution should be as low as possible,optimally less than 20%and 3μm,for characterization of higher-mode signatures such as Ps-P12 by x-ray self-emission images.On the contrary,signatures of lower-mode such as P2 remain clear at all contour levels and spatial resolutions.These key results can help determine the optimal diagnostics,laser,and target parameters for implosion experiments.Recent typical hot-spot asymmetry measurements and applications on the Shenguang 100 kJ class laser facility are also reported.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10635050)
文摘We investigated the radiation characteristics and implosion dynamics of low-wire-number cylindrical tungsten wire array Z-pinches on the YANG accelerator with a peak current 0.8-1.1 MA and a rising time ～ 90 ns.The arrays are made up of（8-32）×5 μm wires 6/10 mm in diameter and 15 mm in height.The highest X-ray power obtained in the experiments was about 0.37 TW with the total radiation energy ～ 13 kJ and the energy conversion efficiency ～ 9%（24×5 μm wires,6 mm in diameter）.Most of the X-ray emissions from tungsten Z-pinch plasmas were distributed in the spectral band of 100-600 eV,peaked at 250 and 375 eV.The dominant wavelengths of the wire ablation and the magneto-Rayleigh-Taylor instability were found and analyzed through measuring the time-gated self-emission and laser interferometric images.Through analyzing the implosion trajectories obtained by an optical streak camera,the run-in velocities of the Z-pinch plasmas at the end of the implosion phase were determined to be about（1.3-2.1）×10 7 cm/s.
文摘Purpose: The purpose of this study is to introduce a new concept and term into the scientometric discourse and research—scientometric implosion—and test the idea on the example of the Armenian journals. The article argues that the existence of a compressed scientific area in the country makes pressure on the journals and after some time this pressure makes one or several journals explode—break the limited national scientific area and move to the international arena. As soon as one of the local journals breaks through this compressed space and appears at an international level, further explosion happens, which makes the other journals follow the same path.Design/methodology/approach: Our research is based on three international scientific databases—WoS, Scopus, and RISC CC, from where we have retrieved information about the Armenian journals indexed there and citations received by those journals and one national database—the Armenian Science Citation Index. Armenian Journal Impact Factor(ArmJIF) was calculated for the local Armenian journals based on the general impact factor formula. Journals were classified according to Gl?nzel and Schubert(2003). Findings: Our results show that the science policy developed by the scientific authorities of Armenia and the introduction of ArmJIF have made the Armenian journals comply with international standards and resulted in some local journals to break the national scientific territory and be indexed in international scientific databases of RISC, Scopus, and WoS. Apart from complying with technical requirements, the journals start publishing articles also in foreign languages. Although nearly half of the local journals are in the fields of social sciences and humanities, only one journal from that field is indexed in international scientific databases. Research limitation: One of the limitations of the study is that it was performed on the example of only one state and the second one is that more time passage is needed to firmly evaluate the results. However, the introduction of the concept can inspire other similar case study. Practical implications: The new term and relevant model offered in the article can practically be used for the development of national journals.Originality/value: The article proposes a new term and a concept in scientometrics.
基金This work was supported by the National Natural Science Foundation of China No.10035020.
文摘A magnetohydrodynamic (MHD) formulation is derived to investigate and compare the mitigation effects of both the sheared axial flow and finite Larmor radius (FLR) on the Rayleigh-Taylor (RT) instability in Z-pinch implosions. The sheared axial flow is introduced into MHD equations in a conventional way and the FLR effect into the equations via /t → -i(w+ik⊥2pi2Ωi,), as proposed in our previous paper [Chin. Phys. Lett. 2002, 19:217] , where k⊥2 pi2 is referred to FLR effect from the general kinetic theory of magnetized plasma. Therefore the linearized continuity and momentum equations for the perturbed mass-density and velocity include both the sheared axial flow and the FLR effect. It is found that the effect of sheared axial flow with a lower peak velocity can mitigate RT instability in the whole wavenumber region and the effect of sheared axial flow with a higher one can mitigate RT instability only in the large wavenumber region (for normalized wavenumber k】2.4); The effect of FLR can mitigate RT instability in the whole wavenumber region and the mitigation effect is stronger than that of the sheared axial flow with a lower peak velocity in the almost whole wavenumber region.
基金The project supported by the National High Technology Development Program of China (No. 863-804-3)
文摘The neutron Doppler broadening in inertial confinement fusion has been acquired from the time of flight for the neutron, from which the fuel ion temperature can be derived. An ultrafast-quenched plastic scintillation detector was used to measure the time of flight for the neutron at a low-imploded DT neutron yield (5×107-1×108) in the experiment performed on the Shenguang Ⅱ laser facility. The typical temperatures of ablating targets for indirect drive were around 2.8 keV and the uncertainties were ±30 % - ±40%. The detection efficiency of the detector for DT neutrons was calibrated at a K-400 accelerator. The time response function of the detection system was calibrated by imploded neutrons from a DT-filled capsule, which can be regarded as a S function pulsed neutron source due to its much narrower pulse width than that of the measured neutron time-of-flight spectrum.
基金Project supported by the NSAF Joint Fund set up by the National Natural Science Foundation of China and the Chinese Academy of Engineering Physics (CAEP)(Nos. 10676005, 10676004, and10676120)the National Natural Science Foundation of China (No. 10702011)+1 种基金the Natural Science Foundation of CAEP (No. 2007B09001)the Scientific Research Foundation for Returned Overseas Chinese Scholars of Ministry of Education of China
文摘This paper generalizes the single-shell Kidder＇s self-similar solution to the double-shell one with a discontinuity in density across the interface. An isentropic implosion model is constructed to study the Rayleigh-Taylor instability for the implosion compression. A Godunov-type method in the Lagrangian coordinates is used to compute the one-dimensional Euler equation with the initial and boundary conditions for the double-shell Kidder＇s self-similar solution in spherical geometry. Numerical results are obtained to validate the double-shell implosion model. By programming and using the linear perturbation codes, a linear stability analysis on the Rayleigh-Taylor instability for the double-shell isentropic implosion model is performed. It is found that, when the initial perturbation is concentrated much closer to the interface of the two shells, or when the spherical wave number becomes much smaller, the modal radius of the interface grows much faster, i.e., more unstable. In addition, from the spatial point of view for the compressibility effect on the perturbation evolution, the compressibility of the outer shell has a destabilization effect on the Rayleigh-Taylor instability, while the compressibility of the inner shell has a stabilization effect.
文摘Chimney implosion is the strategic planning of explosives and accessories materials and timings of its detonation so that chimney collapses on itself, minimising the physical damage to its immediate surroundings. Built in 1885, the brick chimney at kankanee colliery, Sijua area, BCCL （Bharat Collieries Company Limited） was demolished by felling method using the commercial explosives by adopting single-folding and toppling method. The chimney was 31.5 m in height and suffered structural weaknesses due to progressive deterioration over age, weathering and non maintenance. The chimney was posing potential threat to the safety of the nearby dwellings and surface structures, viz. main mechanical ventilator of Kankanee colliery, 11 KV electrical substation supplying power to Sijua area, BCCL, high tension cable line and busy Katras-Sijua-Dhanbad Dobari Road all failing within a radius of 30 m. About 75.22 kg of commercial explosive, 100 m of detonating fuse along with 0 and 25 ms delay detonators were used for controlled demolition of chimney. The chimney got demolished by vertically cascading on its own base without causing any damage to the nearby dwellings and surface structures.
基金support from the National Natural Sciences Foundation of China(U2067220,51779139)the Young Talent Project of China National Nuclear Corporation,and Project of Top Young Talents of Ten Thousand Talents Plan.
文摘Due to sophistications in experimental studies,the implosions in chain reaction,also named as sympathetic implosions,demand numerical models to understand the phenomena caused by various impacts to the primary sphere.We developed a 3D air-solid-water model considering the influence of brittle sphere failures of two alumina spheres to simulate the outbreak of the sympathetic implosion in the seawater of 114 MPa.According to the triggering mode,two cases of simultaneous implosions and five cases of sympathetic implosions of a double-sphere were numerically studied.We found that the induced fracture of the secondary sphere happened before the outbreak of the positive pressure wave,i.e.,the induced fracture is caused by the uneven pressure around the sphere lower than the hydrostatic pressure.To our knowledge,the present paper is the first report on the early fracture of the secondary solid sphere in sympathetic implosions.With various triggering modes of the primary sphere,the secondary fractures are all induced at the proximal side and extend to the other side.The formed ring-shaped implosion cores are caused by individual fracture mode.The shifting of the two implosion cores eventually affects the pressure pulses at a position.A higher or similar values of the secondary pulse are found closely related to the double sphere’s fracture modes,i.e.,related to the triggering modes of the local impacts.This work help to estimate the damage of the sympathetic implosion to the surroundings,and prevent further implosions by understanding spatial superposition of a series of pulses.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDA25050200 and XDA25010100)the National Natural Science Foundation of China(Grant Nos.12175309,12475252,12275356 and 12075317)the Defense Industrial Technology Development Program(Grant No.CKYS2023212807).
文摘The double-cone ignition scheme is a promising novel ignition method,which is expected to greatly save the driver energy and enhance the robustness of the implosion process.In this paper,ablation of the inner surface of the cone by the hard X-ray from coronal Au plasma is studied via radiation hydrodynamics simulations.It is found that the X-ray ablation of the inner wall will form strong pre-plasma,which will significantly affect the implosion process and cause the Au plasma to mix with the fuel,leading to ignition failure.The radiation and pre-ablation intensities in the system are estimated,and the evolutions of areal density,ion temperature and the distribution of Au ions are analysed.In addition,the mixing of Au in CH at collision is quantified.Then,a scheme to reduce the X-ray pre-ablation by replacing the gold cone with a tungsten cone is proposed,showing that it is effective in reducing high-Z mixing and improving collision results.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant Nos.12074399,12204500,and 12004403)the Key Projects of the Intergovernmental International Scientifi and Technological Innovation Cooperation(Grant No.2021YFE0116700)+1 种基金the Shanghai Natural Science Foundation(Grant No.20ZR1464400)the Shanghai Sailing Program(Grant No.22YF1455300)。
文摘The effect of drive laser wavelength on the growth of ablative Rayleigh–Taylor instability(ARTI)in inertial confinemen fusion(ICF)is studied with two-dimensional numerical simulations.The results show that in the plasma acceleration phase,shorter wavelengths lead to more efficien coupling between the laser and the kinetic energy of the implosion fluid Under the condition that the laser energy coupled to the implosion flui is constant,the ARTI growth rate decreases as the laser wavelength moves toward the extreme ultraviolet band,reaching its minimum value near λ=65 nm,and when the laser wavelength continuously moves toward the X-ray band,the ARTI growth rate increases rapidly.It is found that the results deviate from the theoretical ARTI growth rate.As the laser intensity benchmark increases,the position of the minimum ARTI growth rate shifts toward shorter wavelengths.As the initial sinusoidal perturbation wavenumber decreases,the position of the minimum ARTI growth rate shifts toward longer wavelengths.We believe that the conclusions drawn from the present simulations and analysis will help provide a better understanding of the ICF process and improve the theory of ARTI growth.
基金the support from the National Natural Sciences Foundation of China(51779139,U2067220)the National Key Research and Development Program of China(Grant No.2016YFC0300700)+1 种基金Shanghai Talent Development Funding(2018029)the Young Talent Project of China National Nuclear Corporation.
文摘Pressure hulls play an important role in deep-sea underwater vehicles.However,in the ultra-high pressure environment,a highly destructive phenomenon could occur to them which is called implosion.To study the characteristics of the flow field of the underwater implosion of hollow ceramic pressure hulls,the compressible multiphase flow theory,direct numerical simulation,and adaptive mesh refinement are used to numerically simulate the underwater implosion of a single ceramic pressure hull and multiple linearly arranged ceramic pressure hulls.Firstly,the feasibility of the numerical simulation method is verified.Then,the results of the flow field of the underwater implosion of hollow ceramic pressure hulls in 11000 m depth is analyzed.There are the compression-rebound processes of the internal air cavity in the implosion.In the rebound stage,a shock wave that is several times the ambient pressure is generated outside the pressure hull,and the propagation speed is close to the speed of sound.The pressure peak of the shock wave has a negative exponential power function relationship with the distance to the center of the sphere.Finally,it is found that the obvious superimposed effect between spheres exists in the chain-reaction implosion which enhances the implosion shock wave.
基金supported by the National Natural Science Foundation of China(Grant Nos.11275031,11675026,11475032,11475034,11575033,and 11274026)the Foundation of President of Chinese Academy of Engineering Physics(Grant No.2014-1-040)the National Basic Research Program of China(Grant No.2013CB834100)
文摘Inertial fusion energy （IFE） has been considered a promising, nearly inexhaustible source of sustainable carbon-free power for the world＇s energy future. It has long been recognized that the control of hydrodynamic instabilities is of critical importance for ignition and high-gain in the inertial-confinement fusion （ICF） hot-spot ignition scheme. In this mini-review, we summarize the progress of theoretical and simulation research of hydrodynamic instabilities in the ICF central hot-spot implosion in our group over the past decade. In order to obtain sufficient understanding of the growth of hydrodynamic instabilities in ICF, we first decompose the problem into different stages according to the implosion physics processes. The decomposed essential physics pro- cesses that are associated with ICF implosions, such as Rayleigh-Taylor instability （RTI）, Richtmyer-Meshkov instability （RMI）, Kelvin-Helmholtz instability （KHI）, convergent geometry effects, as well as perturbation feed-through are reviewed. Analyti- cal models in planar, cylindrical, and spherical geometries have been established to study different physical aspects, including density-gradient, interface-coupling, geometry, and convergent effects. The influence of ablation in the presence of preheating on the RTI has been extensively studied by numerical simulations. The KHI considering the ablation effect has been discussed in detail for the first time. A series of single-mode ablative RTI experiments has been performed on the Shenguang-II laser facility. The theoretical and simulation research provides us the physical insights of linear and weakly nonlinear growths, and nonlinear evolutions of the hydrodynamic instabilities in ICF implosions, which has directly supported the research of ICF ignition target design. The ICF hot-spot ignition implosion design that uses several controlling features, based on our current understanding of hydrodynamic instabilities, to address shell implosion stability, has been briefly described, several of which are novel.
基金supported by the Japan Society for the Promotion of Science(JSPS)。
文摘Microtube implosions are a novel scheme to generate ultrahigh magnetic fields of the megatesla order.These implosions are driven by ultraintense and ultrashort laser pulses.Using two-and three-dimensional particle simulations where megatesla-order magnetic fields can be achieved,we demonstrate scaling and criteria in terms of laser parameters,such as laser intensity and laser energy,to facilitate practical experiments toward the realization of extreme physical conditions,which have yet to be realized in laboratories.Microtube implosions should provide a new platform for studies in fundamental and applied physics relevant to ultrahigh magnetic fields.
基金supported by JSPS,MEXT,CORE(Center for Optical Research and Education,Utsunomiya University),ASHULA,ILE/Osaka University,and CDI(Cre-ative Department for Innovation,Utsunomiya University).
文摘In this review paper on heavy ion inertial fusion(HIF),the state-of-the-art scientific results are presented and discussed on the HIF physics,including physics of the heavy ion beam(HIB)transport in a fusion reactor,the HIBs-ion illumination on a direct-drive fuel target,the fuel target physics,the uniformity of the HIF target implosion,the smoothing mechanisms of the target implosion non-uniformity and the robust target implosion.The HIB has remarkable preferable features to release the fusion energy in inertial fusion:in particle accelerators HIBs are generated with a high driver efficiency of~30%-40%,and the HIB ions deposit their energy inside of materials.Therefore,a requirement for the fusion target energy gain is relatively low,that would be~50-70 to operate a HIF fusion reactor with the standard energy output of 1 GWof electricity.The HIF reactor operation frequency would be~10-15 Hz or so.Several-MJ HIBs illuminate a fusion fuel target,and the fuel target is imploded to about a thousand times of the solid density.Then the DT fuel is ignited and burned.The HIB ion deposition range is defined by the HIB ions stopping length,which would be~1 mm or so depending on the material.Therefore,a relatively large density-scale length appears in the fuel target material.One of the critical issues in inertial fusion would be a spherically uniform target compression,which would be degraded by a non-uniform implosion.The implosion non-uniformity would be introduced by the Rayleigh-Taylor(R-T)instability,and the large densitygradient-scale length helps to reduce the R-T growth rate.On the other hand,the large scale length of the HIB ions stopping range suggests that the temperature at the energy deposition layer in a HIF target does not reach a very-high temperature:normally about 300 eV or so is realized in the energy absorption region,and that a direct-drive target would be appropriate in HIF.In addition,the HIB accelerators are operated repetitively and stably.The precise control of the HIB axis manipulation is also realized in the HIF accelerator,and the HIB wobbling motion may give another tool to smooth the HIB illumination non-uniformity.The key issues in HIF physics are also discussed and presented in the paper.
