Recent experiments on the implosions of 15-mm long and 2-μm thick aluminum liners having a diameter of 12.8 mm have been performed on the primary test stand(PTS) facility. The stratified structures are observed as al...Recent experiments on the implosions of 15-mm long and 2-μm thick aluminum liners having a diameter of 12.8 mm have been performed on the primary test stand(PTS) facility. The stratified structures are observed as alternating dark and light transverse stripes in the laser shadowgraph images. These striations perpendicular to the current flow are formed early in the implosion, i.e., at the stage when the bulk of the material mass was almost at rest. A two-dimensional(2 D)magnetohydrodynamics(MHD) code is employed to simulate the behavior of liner dynamics in the early phases. It is found that the striations may be produced by the electrothermal instability(ETI) that results from non-uniform Joule heating due to the characteristic relation between the resistivity and the temperature. In 2 D simulations, the stratified structures can be seen obviously in both density and temperature contours as the liner expands rapidly. By analyzing instability spectrum, the dominant wavelengths of the perturbations are 8.33 μm–20.0 μm, which agree qualitatively with the theoretical predictions.It is also interesting to show that ETI provides a significant seed to the subsequent magneto Rayleigh–Taylor(MRT)instability.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
In fast Z-pinches,rise time of drive current plays an important role in development of magneto-Rayleigh–Taylor(MRT)instabilities.It is essential for applications of Z-pinch dynamic hohlraum(ZPDH),which could be used ...In fast Z-pinches,rise time of drive current plays an important role in development of magneto-Rayleigh–Taylor(MRT)instabilities.It is essential for applications of Z-pinch dynamic hohlraum(ZPDH),which could be used for driving inertial confinement fusion(ICF),to understand the scaling of rise time on MRTs.Therefore,a theoretical model for nonlinear development of MRTs is developed according to the numerical analysis.It is found from the model that the implosion distance L=r_(0)-r_(mc)determines the development of MRTs,where r_(0)is the initial radius and rmc is the position of the accelerating shell.The current rise timeτwould affect the MRT development because of its strong coupling with the r;.The amplitude of MRTs would increase with the rise time linearly if an implosion velocity is specified.The effects of the rise time on MRT,in addition,are studied by numerical simulation.The results are consistent with those of the theoretical model very well.Finally,the scaling of the rise time on amplitude of MRTs is obtained for a specified implosion velocity by the theoretical model and numerical simulations.展开更多
We apply the reductive perturbation method to the simple electrostatic ion-temperature-gradient mode in an advanced fluid description. The fluid resonance turns out to play a major role for the excitation of zonal flo...We apply the reductive perturbation method to the simple electrostatic ion-temperature-gradient mode in an advanced fluid description. The fluid resonance turns out to play a major role for the excitation of zonal flows. This is the mechanism recently found to lead to the low-to-high （L-H） mode transition and to the nonlinear Dimits upshift in transport code simulations. It is important that we have taken the nonlinear temperature dynamics from the Reynolds stress as the convected diamagnetic flow. This has turned out to be the most relevant effect as found in transport simulations of the L-H transition, internal transport barriers and Dimits shift. This is the first time that an analytical method is applied to a system which numerically has been found to give the right experimental dynamics.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11805019,11775032,11605013,and 11705013)
文摘Recent experiments on the implosions of 15-mm long and 2-μm thick aluminum liners having a diameter of 12.8 mm have been performed on the primary test stand(PTS) facility. The stratified structures are observed as alternating dark and light transverse stripes in the laser shadowgraph images. These striations perpendicular to the current flow are formed early in the implosion, i.e., at the stage when the bulk of the material mass was almost at rest. A two-dimensional(2 D)magnetohydrodynamics(MHD) code is employed to simulate the behavior of liner dynamics in the early phases. It is found that the striations may be produced by the electrothermal instability(ETI) that results from non-uniform Joule heating due to the characteristic relation between the resistivity and the temperature. In 2 D simulations, the stratified structures can be seen obviously in both density and temperature contours as the liner expands rapidly. By analyzing instability spectrum, the dominant wavelengths of the perturbations are 8.33 μm–20.0 μm, which agree qualitatively with the theoretical predictions.It is also interesting to show that ETI provides a significant seed to the subsequent magneto Rayleigh–Taylor(MRT)instability.
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supported by the National Natural Science Foundation of China(Grant Nos.11975057,11605013,11775023,and 11705013)。
文摘In fast Z-pinches,rise time of drive current plays an important role in development of magneto-Rayleigh–Taylor(MRT)instabilities.It is essential for applications of Z-pinch dynamic hohlraum(ZPDH),which could be used for driving inertial confinement fusion(ICF),to understand the scaling of rise time on MRTs.Therefore,a theoretical model for nonlinear development of MRTs is developed according to the numerical analysis.It is found from the model that the implosion distance L=r_(0)-r_(mc)determines the development of MRTs,where r_(0)is the initial radius and rmc is the position of the accelerating shell.The current rise timeτwould affect the MRT development because of its strong coupling with the r;.The amplitude of MRTs would increase with the rise time linearly if an implosion velocity is specified.The effects of the rise time on MRT,in addition,are studied by numerical simulation.The results are consistent with those of the theoretical model very well.Finally,the scaling of the rise time on amplitude of MRTs is obtained for a specified implosion velocity by the theoretical model and numerical simulations.
基金Supported by the JSPS-NRF-NSFC A3 Foresight Program in the Field of Plasma Physics under Grant Nos 11261140328 and 2012K2A2A6000443the ’Thirteenth Five-Year’ Strategic Planning of Chinathe Funds of the Chinese Academy of Sciences and ASIPP
文摘We apply the reductive perturbation method to the simple electrostatic ion-temperature-gradient mode in an advanced fluid description. The fluid resonance turns out to play a major role for the excitation of zonal flows. This is the mechanism recently found to lead to the low-to-high （L-H） mode transition and to the nonlinear Dimits upshift in transport code simulations. It is important that we have taken the nonlinear temperature dynamics from the Reynolds stress as the convected diamagnetic flow. This has turned out to be the most relevant effect as found in transport simulations of the L-H transition, internal transport barriers and Dimits shift. This is the first time that an analytical method is applied to a system which numerically has been found to give the right experimental dynamics.
