Experimental investigation of the compression and heating of an MHD-driven jet impacting a target cloud
Experimental investigation of the compression and heating of an MHD-driven jet impacting a target cloud
复制标题
MHD 驱动射流撞击目标云的压缩和加热实验研究
作者：
B. Seo;P. Bellan
通过 MHD 驱动的等离子体射流撞击气体目标云来研究绝热压缩。观察了撞击时射流的压缩和加热情况，并与理论预测进行了比较。全面测量的诊断包括汤姆逊散射系统、快速电影摄影机、可平移光纤耦合干涉仪、单色仪、可见光光电二极管和磁探针阵列。使用这些诊断进行的测量提供了与时间相关的电子密度、电子温度、连续发射、线发射和磁场分布。在压缩过程中观察到密度和磁场增加以及射流速度降低。电子温度具有复杂的时间依赖性，首先升高，然后在不到 1 μs 的时间内迅速下降，这小于总压缩时间。分析表明，这种突然的温度下降是高密度压缩等离子体中三体重组自发产生的氢原子辐射损失的结果。不仅针对加州理工学院的实验，而且还针对聚变级机制，讨论了压缩速度必须有多快才能超过辐射损失的标准。此外，还在冲击的背景下分析了结果，并将冲击的影响与绝热压缩进行了比较。通过使 MHD 驱动的等离子体射流撞击气体目标云来研究绝热压缩。观察了撞击时射流的压缩和加热情况，并与理论预测进行了比较。全面测量的诊断包括汤姆逊散射系统、快速电影摄影机、可平移光纤耦合干涉仪、单色仪、可见光光电二极管和磁探针阵列。使用这些诊断进行的测量提供了与时间相关的电子密度、电子温度、连续发射、线发射和磁场分布。在压缩过程中观察到密度和磁场增加以及射流速度降低。电子温度具有复杂的时间依赖性，首先升高，然后在不到 1 μs 的时间内迅速下降，这小于总压缩时间。分析表明，这种突然的温度下降是通过三层自发产生的氢原子辐射损失的结果……
Adiabatic compression has been investigated by having an MHD-driven plasma jet impact a gas target cloud. Compression and heating of the jet upon impact were observed and compared to theoretical predictions. Diagnostics for comprehensive measurements included a Thomson scattering system, a fast movie camera, a translatable fiber-coupled interferometer, a monochromator, a visible-light photodiode, and a magnetic probe array. Measurements using these diagnostics provided the time-dependent electron density, electron temperature, continuum emission, line emission, and magnetic field profile. Increases in density and magnetic field and a decrease in jet velocity were observed during the compression. The electron temperature had a complicated time dependence, increasing at first, but then rapidly declining in less than 1 μs which is less than the total compression time. Analysis indicates that this sudden temperature drop is a consequence of radiative loss from hydrogen atoms spontaneously generated via three-body recombination in the high-density compressed plasma. A criterion for how fast compression must be to outrun radiative loss is discussed not only for the Caltech experiment but also for fusion-grade regimes. In addition, the results are analyzed in the context of shocks the effects of which are compared to adiabatic compression.Adiabatic compression has been investigated by having an MHD-driven plasma jet impact a gas target cloud. Compression and heating of the jet upon impact were observed and compared to theoretical predictions. Diagnostics for comprehensive measurements included a Thomson scattering system, a fast movie camera, a translatable fiber-coupled interferometer, a monochromator, a visible-light photodiode, and a magnetic probe array. Measurements using these diagnostics provided the time-dependent electron density, electron temperature, continuum emission, line emission, and magnetic field profile. Increases in density and magnetic field and a decrease in jet velocity were observed during the compression. The electron temperature had a complicated time dependence, increasing at first, but then rapidly declining in less than 1 μs which is less than the total compression time. Analysis indicates that this sudden temperature drop is a consequence of radiative loss from hydrogen atoms spontaneously generated via three-...