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
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
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
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
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
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
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
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
Rayleigh-Taylor instability of three fluid layers with two interfaces in cylindrical geometry is investigated analytically. The growth rates and the amplitudes of perturbation on the two interfaces are obtained. The f...Rayleigh-Taylor instability of three fluid layers with two interfaces in cylindrical geometry is investigated analytically. The growth rates and the amplitudes of perturbation on the two interfaces are obtained. The feedback factor from outer to inner interface is larger than that from inner to outer interface under the same conditions. The growth rate on the initially unstable interface is larger than the corresponding result in planar geometry for low mode perturbation. The two interfaces are decoupled for a larger mode number perturbation. The dependencies of the amplitudes of perturbation on different initial conditions are analyzed. The negative feedback effect from initially stable interface to another unstable interface is observed. In the limit of infinity inner radius and finite shell thickness, the results in planar geometry are recovered.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
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 assembling stabilizing effect of the finite Larmor radius (FLR) and the sheared axial flow (SAF) on the Rayleigh-Taylor instability in Z-pinch implosions is studied by means of the incompressible finite Larmor rad...The assembling stabilizing effect of the finite Larmor radius (FLR) and the sheared axial flow (SAF) on the Rayleigh-Taylor instability in Z-pinch implosions is studied by means of the incompressible finite Larmor radius magnetohydrodynamic (MHD) equations. The finite Larmor radius effects are introduced in the momentum equation with the sheared axial flow through an anisotropic ion stress tensor. In this paper a linear mode equation is derived that is valid for arbitrary kL, where k is the wave number and L is the plasma shell thickness. Numerical solutions are presented. The results indicate that the short-wavelength modes of the Rayleigh-Taylor instability are easily stabilized by the individual effect of the finite Larmor radius or the sheared axial flow. The assembling effects of the finite Larmor radius and sheared axial flow can heavily mitigate the Rayleigh-Taylor instability, and the unstable region can be compressed considerably.展开更多
X-ray drive asymmetry is one of the main seeds of low-mode implosion asymmetry that blocks further improvement of the nuclear per-formance of“high-foot”experiments on the National Ignition Facility[Miller et al.,Nuc...X-ray drive asymmetry is one of the main seeds of low-mode implosion asymmetry that blocks further improvement of the nuclear per-formance of“high-foot”experiments on the National Ignition Facility[Miller et al.,Nucl.Fusion 44,S228(2004)].More particularly,the P2 asymmetry of Au's M-band flux can also severely influence the implosion performance of ignition capsules[Li et al.,Phys.Plasmas 23,072705(2016)].Here we study the smoothing effect of mid-and/or high-Z dopants in ablator on Au's M-band flux asymmetries,by modeling and comparing the implosion processes of a Ge-doped ignition capsule and a Si-doped one driven by X-ray sources with P2 M-band flux asymmetry.As the results,(1)mid-or high-Z dopants absorb hard X-rays(M-band flux)and re-emit isotropically,which helps to smooth the asymmetric M-band flux arriving at the ablation front,therefore reducing the P2 asymmetries of the imploding shell and hot spot;(2)the smoothing effect of Ge-dopant is more remarkable than Si-dopant because its opacity in Au's M-band is higher than the latter's;and(3)placing the doped layer at a larger radius in ablator is more efficient.Applying this effect may not be a main measure to reduce the low-mode implosion asymmetry,but might be of significance in some critical situations such as inertial confinement fusion(ICF)experiments very near the performance cliffs of asymmetric X-ray drives.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
The primary DD proton spectrum is used for diagnosing the fuel-shell areal density pR of imploded capsules on Shenguang Ⅲ （SG-Ⅲ） prototype laser facility for the first time. A charged particle spectrometer （CPS）...The primary DD proton spectrum is used for diagnosing the fuel-shell areal density pR of imploded capsules on Shenguang Ⅲ （SG-Ⅲ） prototype laser facility for the first time. A charged particle spectrometer （CPS） with a CR39 nuclear track detector is used to measure the DD proton spectrum. The proton spectrum is determined from both the proton track and its size. A typical proton energy peak shift from 3.02 MeV to 2.6 MeV is observed in our experiment, which yields a maximum pR larger than 6 mg/cm2.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
The basic concept of fast Z-pinch,and late progress in fast Z-pinch plasma research as HEDP and ICF research,especially as an approach for high yield low-cost fusion energy research,are summarized in this paper.The po...The basic concept of fast Z-pinch,and late progress in fast Z-pinch plasma research as HEDP and ICF research,especially as an approach for high yield low-cost fusion energy research,are summarized in this paper.The possible technical challenges of fast Z-pinch-driven ICF as fusion energy and it application prospect are discussed.展开更多
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 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 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.
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.
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.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11275031,11475034,11575033,and 11274026)the National Basic Research Program of China(Grant No.2013CB834100)
文摘Rayleigh-Taylor instability of three fluid layers with two interfaces in cylindrical geometry is investigated analytically. The growth rates and the amplitudes of perturbation on the two interfaces are obtained. The feedback factor from outer to inner interface is larger than that from inner to outer interface under the same conditions. The growth rate on the initially unstable interface is larger than the corresponding result in planar geometry for low mode perturbation. The two interfaces are decoupled for a larger mode number perturbation. The dependencies of the amplitudes of perturbation on different initial conditions are analyzed. The negative feedback effect from initially stable interface to another unstable interface is observed. In the limit of infinity inner radius and finite shell thickness, the results in planar geometry are recovered.
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.
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The project supported by the National Natural Science Foundation of China (Nos. 10035020 and 40390150)
文摘The assembling stabilizing effect of the finite Larmor radius (FLR) and the sheared axial flow (SAF) on the Rayleigh-Taylor instability in Z-pinch implosions is studied by means of the incompressible finite Larmor radius magnetohydrodynamic (MHD) equations. The finite Larmor radius effects are introduced in the momentum equation with the sheared axial flow through an anisotropic ion stress tensor. In this paper a linear mode equation is derived that is valid for arbitrary kL, where k is the wave number and L is the plasma shell thickness. Numerical solutions are presented. The results indicate that the short-wavelength modes of the Rayleigh-Taylor instability are easily stabilized by the individual effect of the finite Larmor radius or the sheared axial flow. The assembling effects of the finite Larmor radius and sheared axial flow can heavily mitigate the Rayleigh-Taylor instability, and the unstable region can be compressed considerably.
基金This work is partly supported by the National Natural Science Foundation of China under Grant Nos.11575034,11275031,11475033the Fundamental Research Program of CAEP(Contract No.2013A0102002).
文摘X-ray drive asymmetry is one of the main seeds of low-mode implosion asymmetry that blocks further improvement of the nuclear per-formance of“high-foot”experiments on the National Ignition Facility[Miller et al.,Nucl.Fusion 44,S228(2004)].More particularly,the P2 asymmetry of Au's M-band flux can also severely influence the implosion performance of ignition capsules[Li et al.,Phys.Plasmas 23,072705(2016)].Here we study the smoothing effect of mid-and/or high-Z dopants in ablator on Au's M-band flux asymmetries,by modeling and comparing the implosion processes of a Ge-doped ignition capsule and a Si-doped one driven by X-ray sources with P2 M-band flux asymmetry.As the results,(1)mid-or high-Z dopants absorb hard X-rays(M-band flux)and re-emit isotropically,which helps to smooth the asymmetric M-band flux arriving at the ablation front,therefore reducing the P2 asymmetries of the imploding shell and hot spot;(2)the smoothing effect of Ge-dopant is more remarkable than Si-dopant because its opacity in Au's M-band is higher than the latter's;and(3)placing the doped layer at a larger radius in ablator is more efficient.Applying this effect may not be a main measure to reduce the low-mode implosion asymmetry,but might be of significance in some critical situations such as inertial confinement fusion(ICF)experiments very near the performance cliffs of asymmetric X-ray drives.
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supported by the Foundation of Science and Technology on Plasma Physics Laboratory,China(Grant No.9140C680302130C68243)
文摘The primary DD proton spectrum is used for diagnosing the fuel-shell areal density pR of imploded capsules on Shenguang Ⅲ （SG-Ⅲ） prototype laser facility for the first time. A charged particle spectrometer （CPS） with a CR39 nuclear track detector is used to measure the DD proton spectrum. The proton spectrum is determined from both the proton track and its size. A typical proton energy peak shift from 3.02 MeV to 2.6 MeV is observed in our experiment, which yields a maximum pR larger than 6 mg/cm2.
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National Natural Science Foundation Project(10375010)
文摘The basic concept of fast Z-pinch,and late progress in fast Z-pinch plasma research as HEDP and ICF research,especially as an approach for high yield low-cost fusion energy research,are summarized in this paper.The possible technical challenges of fast Z-pinch-driven ICF as fusion energy and it application prospect are discussed.
