Anisotropy-driven collisional separation of impurities in magnetized compressing and expanding cylindrical plasmas
Anisotropy-driven collisional separation of impurities in magnetized compressing and expanding cylindrical plasmas
复制标题
磁化压缩和膨胀圆柱形等离子体中各向异性驱动的杂质碰撞分离
作者：
I. Ochs;N. Fisch
当圆柱对称磁化等离子体压缩或膨胀时，由于平行于和垂直于磁场的绝热守恒定律不同，自然产生速度空间各向异性。当压缩时间尺度与碰撞时间尺度相当，并且两者都比回转周期长得多时，这种压力各向异性可能变得显著。我们表明，这种自然产生的各向异性可以显着影响的压缩等离子体中的杂质的运输，即使在没有标量的温度或密度梯度，通过修改引起径向粒子运输的方位角摩擦。虽然杂质输运方向只取决于压力各向异性的符号，但各向异性本身取决于磁场的节距大小和径向速度的符号。因此，压力各向异性效应可驱使杂质朝向或远离等离子体核心。这些各向异性相关的条款代表了一种新的效果，影响运输，特别是在稀疏的边缘区域的动态压缩螺旋箍缩等离子体。当圆柱对称磁化等离子体压缩或膨胀时，由于平行于和垂直于磁场方向的绝热守恒定律不同，自然会产生速度空间各向异性。当压缩时间尺度与碰撞时间尺度相当，并且两者都比回转周期长得多时，这种压力各向异性可能变得显著。我们表明，这种自然产生的各向异性可以显着影响的压缩等离子体中的杂质的运输，即使在没有标量的温度或密度梯度，通过修改引起径向粒子运输的方位角摩擦。虽然杂质输运方向只取决于压力各向异性的符号，但各向异性本身取决于磁场的节距大小和径向速度的符号。因此，压力各向异性效应可驱使杂质朝向或远离等离子体核心。这些各向异性依赖项表示。
When a cylindrically symmetric magnetized plasma compresses or expands, velocity-space anisotropy is naturally generated as a result of the different adiabatic conservation laws parallel and perpendicular to the magnetic field. When the compression timescale is comparable to the collision timescale, and both are much longer than the gyroperiod, this pressure anisotropy can become significant. We show that this naturally generated anisotropy can dramatically affect the transport of impurities in the compressing plasma, even in the absence of scalar temperature or density gradients, by modifying the azimuthal frictions that give rise to radial particle transport. Although the impurity transport direction depends only on the sign of the pressure anisotropy, the anisotropy itself depends on the pitch magnitude of the magnetic field and the sign of the radial velocity. Thus, pressure anisotropy effects can drive impurities either towards or away from the plasma core. These anisotropy-dependent terms represent a qualitatively new effect, influencing transport particularly in the sparse edge regions of dynamically compressing screw pinch plasmas. Such plasmas are used for both X-ray generation and magneto-inertial fusion, applications which are sensitive to impurity concentrations.When a cylindrically symmetric magnetized plasma compresses or expands, velocity-space anisotropy is naturally generated as a result of the different adiabatic conservation laws parallel and perpendicular to the magnetic field. When the compression timescale is comparable to the collision timescale, and both are much longer than the gyroperiod, this pressure anisotropy can become significant. We show that this naturally generated anisotropy can dramatically affect the transport of impurities in the compressing plasma, even in the absence of scalar temperature or density gradients, by modifying the azimuthal frictions that give rise to radial particle transport. Although the impurity transport direction depends only on the sign of the pressure anisotropy, the anisotropy itself depends on the pitch magnitude of the magnetic field and the sign of the radial velocity. Thus, pressure anisotropy effects can drive impurities either towards or away from the plasma core. These anisotropy-dependent terms represent ...