For investigating efficiently the stagnation kinetic-process of Z-pinch,we develop a novel modified electrostatic implicit particle-in-cell algorithm in radial one-dimension for Z-pinch simulation in which a small-ang...For investigating efficiently the stagnation kinetic-process of Z-pinch,we develop a novel modified electrostatic implicit particle-in-cell algorithm in radial one-dimension for Z-pinch simulation in which a small-angle cumulative binary collision algorithm is used.In our algorithm,the electric field in z-direction is solved by a parallel electrode-plate model,the azimuthal magnetic field is obtained by Ampere’s law,and the term for charged particle gyromotion is approximated by the cross product of the averaged velocity and magnetic field.In simulation results of 2 MA deuterium plasma shell Zpinch,the mass-center implosion trajectory agrees generally with that obtained by one-dimensional MHD simulation,and the plasma current also closely aligns with the external current.The phase space diagrams and radial-velocity probability distributions of ions and electrons are obtained.The main kinetic characteristic of electron motion is thermal equilibrium and oscillation,which should be oscillated around the ions,while that of ion motion is implosion inwards.In the region of stagnation radius,the radial-velocity probability distribution of ions transits from the non-equilibrium to equilibrium state with the current increasing,while of electrons is basically the equilibrium state.When the initial ion density and current peak are not high enough,the ions may not reach their thermal equilibrium state through collisions even in its stagnation phase.展开更多
Z-pinch experiments with two arrays consisting, respectively, of 32 4-μm- and 6-μm-diameter tungsten wires have been carried out on QiangGuang-1 facility with a current rising up to 1.5 MA in 80 ns. At early time of...Z-pinch experiments with two arrays consisting, respectively, of 32 4-μm- and 6-μm-diameter tungsten wires have been carried out on QiangGuang-1 facility with a current rising up to 1.5 MA in 80 ns. At early time of implosion, x-ray framing images show that the initial emission comes from the central part of arrays, and double clear emission rings, drifting to the anode and the cathode at 5×10^6 cm/s and 2.4×10^7 cm/s respectively, are often produced near the electrodes. Later, in a 4-μm-diameter tungsten wire array, filamentation caused by ohmic heating is prominent, and more than ten filaments have been observed. A radial inward shift of arrays starts at about 30 ns earlier than the occurrence of the x-ray peak power for both kinds of arrays, and the shrinkage rate of emission region is as high as 1.7×107 cm/s in a 4-μm-diameter tungsten wire array, which is two times higher than that in a 6-μm one. Emission from precursor plasmas is observed in implosion of 6-μm-diameter tungsten wire arrays, but not in implosion of a 4- μm-diameter tungsten wire array. Whereas, in a 4-μm-diameter tungsten wire array, the soft x-ray emission shows the growth of m=l instability in the plasma column, which is caused by current. The reasons for the discrepancy between implosions of 4-μm- and 6-μm-diameter tungsten wire arrays are explained.展开更多
Dense Z-pinch plasmas are powerful and energy-efficient laboratory sources of X-rays,and show the possibility to drive inertial confinement fusion(ICF).Recent advances in wire-array Z-pinch and Z-pinch dynamic hohlrau...Dense Z-pinch plasmas are powerful and energy-efficient laboratory sources of X-rays,and show the possibility to drive inertial confinement fusion(ICF).Recent advances in wire-array Z-pinch and Z-pinch dynamic hohlraum(ZPDH)researches at the Institute of Applied Physics and Computational Mathematics are presented in this paper.Models are setup to study different physical processes.A full circuit model(FCM)was used to study the coupling between Z-pinch implosion and generator discharge.A mass injection model with azimuthal modulation was setup to simulate the wire-array plasma initiation,and the two-dimensional MHD code MARED was developed to investigate the Z-pinch implosion,MRT instability,stagnation and radiation.Implosions of nested and quasi-spherical wire arrays were also investigated theoretically and numerically.Key processes of ZPDH,such as the arrayefoam interaction,formation of the hohlraum radiation,as well as the following capsule ablation and implosion,were analyzed with different radiation magneto-hydrodynamics(RMHD)codes.An integrated 2D RMHD simulation of dynamic hohlraum driven capsule implosion provides us the physical insights of wire-array plasma acceleration,shock generation and propagation,hohlraum formation,radiation ablation,and fuel compression.展开更多
Two curved crystal spectrometers are set up on the ＂QiangGuang-1＂ generator to measure the z-pinch plasma spectra emitted from planar aluminum wire array loads. Kodak Biomax-MS film and an IRD AXUVHS5# array are emp...Two curved crystal spectrometers are set up on the ＂QiangGuang-1＂ generator to measure the z-pinch plasma spectra emitted from planar aluminum wire array loads. Kodak Biomax-MS film and an IRD AXUVHS5# array are employed to record time-integrated and time-resolved free-bound radiation, respectively. The photon energy recorded by each detector is ascertained by using the L-shell lines of molybdenum plasma. Based on the exponential relation between the continuum power and photon energies, the aluminum plasma electron temperatures are measured. For the time-integrated diagnosis, several ＂bright spots＂ indicate electron temperatures between （450 eV- 520 eV） ± 35%. And for the time-resolved ones, the result shows that the electron temperature reaches about 800 eV±30% at peak power. The system satisfies the demand of z-pinch plasma electron temperature diagnosis on a - 1 MA facility.展开更多
基金the graduated students Zhixing Feng,Xiaoqiang Zhang,and Deli Fang for their excellent works to develop the PIC simulation codes of Z-pinch.This research was partly supported by the National Natural Science Foundation of China(Grant Nos.11675025 and 11135007)the Innovation Project of China Academy of Engineering Physics(Grant No.CX2019030).
文摘For investigating efficiently the stagnation kinetic-process of Z-pinch,we develop a novel modified electrostatic implicit particle-in-cell algorithm in radial one-dimension for Z-pinch simulation in which a small-angle cumulative binary collision algorithm is used.In our algorithm,the electric field in z-direction is solved by a parallel electrode-plate model,the azimuthal magnetic field is obtained by Ampere’s law,and the term for charged particle gyromotion is approximated by the cross product of the averaged velocity and magnetic field.In simulation results of 2 MA deuterium plasma shell Zpinch,the mass-center implosion trajectory agrees generally with that obtained by one-dimensional MHD simulation,and the plasma current also closely aligns with the external current.The phase space diagrams and radial-velocity probability distributions of ions and electrons are obtained.The main kinetic characteristic of electron motion is thermal equilibrium and oscillation,which should be oscillated around the ions,while that of ion motion is implosion inwards.In the region of stagnation radius,the radial-velocity probability distribution of ions transits from the non-equilibrium to equilibrium state with the current increasing,while of electrons is basically the equilibrium state.When the initial ion density and current peak are not high enough,the ions may not reach their thermal equilibrium state through collisions even in its stagnation phase.
基金Project supported by the National Natural Science Foundation of China （Grant No 10035030）.
文摘Z-pinch experiments with two arrays consisting, respectively, of 32 4-μm- and 6-μm-diameter tungsten wires have been carried out on QiangGuang-1 facility with a current rising up to 1.5 MA in 80 ns. At early time of implosion, x-ray framing images show that the initial emission comes from the central part of arrays, and double clear emission rings, drifting to the anode and the cathode at 5×10^6 cm/s and 2.4×10^7 cm/s respectively, are often produced near the electrodes. Later, in a 4-μm-diameter tungsten wire array, filamentation caused by ohmic heating is prominent, and more than ten filaments have been observed. A radial inward shift of arrays starts at about 30 ns earlier than the occurrence of the x-ray peak power for both kinds of arrays, and the shrinkage rate of emission region is as high as 1.7×107 cm/s in a 4-μm-diameter tungsten wire array, which is two times higher than that in a 6-μm one. Emission from precursor plasmas is observed in implosion of 6-μm-diameter tungsten wire arrays, but not in implosion of a 4- μm-diameter tungsten wire array. Whereas, in a 4-μm-diameter tungsten wire array, the soft x-ray emission shows the growth of m=l instability in the plasma column, which is caused by current. The reasons for the discrepancy between implosions of 4-μm- and 6-μm-diameter tungsten wire arrays are explained.
基金supported by the National Natural Science Fund of China(Nos.11405012,10975022,11275030,11105017,11135007,11471047,91330107)the Foundation of President of China Academy of Engineering Physics(No.2014-1-042)the Defense Industrial Technology Development Program(B1520133015).
文摘Dense Z-pinch plasmas are powerful and energy-efficient laboratory sources of X-rays,and show the possibility to drive inertial confinement fusion(ICF).Recent advances in wire-array Z-pinch and Z-pinch dynamic hohlraum(ZPDH)researches at the Institute of Applied Physics and Computational Mathematics are presented in this paper.Models are setup to study different physical processes.A full circuit model(FCM)was used to study the coupling between Z-pinch implosion and generator discharge.A mass injection model with azimuthal modulation was setup to simulate the wire-array plasma initiation,and the two-dimensional MHD code MARED was developed to investigate the Z-pinch implosion,MRT instability,stagnation and radiation.Implosions of nested and quasi-spherical wire arrays were also investigated theoretically and numerically.Key processes of ZPDH,such as the arrayefoam interaction,formation of the hohlraum radiation,as well as the following capsule ablation and implosion,were analyzed with different radiation magneto-hydrodynamics(RMHD)codes.An integrated 2D RMHD simulation of dynamic hohlraum driven capsule implosion provides us the physical insights of wire-array plasma acceleration,shock generation and propagation,hohlraum formation,radiation ablation,and fuel compression.
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.10905047)
文摘Two curved crystal spectrometers are set up on the ＂QiangGuang-1＂ generator to measure the z-pinch plasma spectra emitted from planar aluminum wire array loads. Kodak Biomax-MS film and an IRD AXUVHS5# array are employed to record time-integrated and time-resolved free-bound radiation, respectively. The photon energy recorded by each detector is ascertained by using the L-shell lines of molybdenum plasma. Based on the exponential relation between the continuum power and photon energies, the aluminum plasma electron temperatures are measured. For the time-integrated diagnosis, several ＂bright spots＂ indicate electron temperatures between （450 eV- 520 eV） ± 35%. And for the time-resolved ones, the result shows that the electron temperature reaches about 800 eV±30% at peak power. The system satisfies the demand of z-pinch plasma electron temperature diagnosis on a - 1 MA facility.
