Escande D F, Paccagnella R, Cappello S, Marchetto C, D'Angelo F
Consorzio RFX, Corso Stati Uniti 4, 35127 Padova, Italy.
Phys Rev Lett. 2000 Oct 9;85(15):3169-72. doi: 10.1103/PhysRevLett.85.3169.
The resilience to chaotic perturbations of one-parameter one-degree-of-freedom Hamiltonian dynamics is shown to increase when its corresponding separatrix vanishes due to a saddle-node bifurcation. This is first highlighted for the magnetic chaos related to quasisingle helicity (QSH) states of the reversed field pinch. It provides a rationale for the confinement improvement of helical structures experimentally found for QSH plasmas; such a feature would not be expected from the classical resonance overlap picture as the separatrix disappearance occurs when the amplitude of the dominant mode increases.
当单参数单自由度哈密顿动力学的相应分界线由于鞍结分岔而消失时，其对混沌微扰的弹性会增强。这首先在与反向场箍缩的准单螺旋度（QSH）状态相关的磁混沌中得到凸显。它为实验中发现的QSH等离子体螺旋结构的约束改善提供了一个理论依据；由于当主导模式的振幅增加时分界线消失，所以从经典的共振重叠图景中无法预期到这样的特征。
