Anomalous pinch flux in tokamaks driven by the longitudinal adiabatic invariant
Anomalous pinch flux in tokamaks driven by the longitudinal adiabatic invariant
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DOI：
10.1063/1.871186
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发表时间：
1995-08
影响因子：
2.2
通讯作者：
J. Nycander;V. Yankov
中科院分区：
文献类型：
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作者：
J. Nycander;V. Yankov
托卡马克中的湍流粒子通量有一个向内的分量，即箍缩通量，它与密度梯度无关。有人提出，这个通量代表的趋势的颗粒分布接近湍流均分，这意味着相空间密度是恒定的超曲面定义的不变量，不被破坏的湍流。对于托卡马克，两个第一绝热不变量给出了被俘获粒子的峰值密度分布n = 1/q。预测偏滤器等离子体的分界线附近的尖锐梯度。箍缩的物理机制如下。当一团被捕获的粒子被湍流涨落向内移动时，它们的平行速度必须增加，以保持纵向不变量J恒定。这相当于绝热压缩，并增加了密度。湍流被认为是由热驱动的静电模式。
The turbulent particle flux in tokamaks has an inward component, the pinch flux, which is independent of the density gradient. It is proposed that this flux represents a tendency of the particle distribution to approach turbulent equipartition, which means that the phase space density is constant on hypersurfaces defined by those invariants that are not destroyed by the turbulence. For tokamaks the two first adiabatic invariants give the peaked density profile n∼1/q of trapped particles. Sharp gradients are predicted near the separatrix of divertor plasmas. The physical mechanism of the pinch is as follows. When a parcel of trapped particles is displaced inward by the turbulent fluctuations, their parallel velocity must increase in order to keep the longitudinal invariant J constant. This is equivalent to adiabatic compression, and increases the density. The turbulence is assumed to be caused by thermally driven electrostatic modes.