Experimental and theoretical investigations of lower hybrid (LH) turbulence in the W7-AS stellarator are presented. The turbulence is excited by an ion beam, which is generated by a weak neutral hydrogen beam injected transversely to the confining magnetic field. The instability is detected by collective Thomson scattering of powerful gyrotron radiation. From the measured density dependence of the frequency it was identified as an LH type of instability. The spectrum is characterized by a narrow bandwidth in spite of the inherently poor radial resolution of the backscattering geometry. The theoretical model of an LH instability driven by a transverse fast ion component under the double resonance condition (coincidence of the LH frequency with a high cyclotron harmonic of the fast ions) is developed. The instability growth rate is derived. The stabilizing effect of high bulk ion temperatures was observed experimentally, in accordance with theoretical modelling. An instability saturation mechanism similar to the well known stochastic ion heating is proposed.
W7-AS恒星器中低混杂（LH）湍流的实验和理论研究被呈现。该湍流由离子束激发，离子束通过注入垂直于约束磁场的弱中性束产生。该不稳定性通过强回旋辐射的集体汤姆逊散射被探测。根据频率对密度的依赖关系，它被识别为LH型不稳定性。尽管背散射几何结构的径向分辨率固有地较差，但谱以窄带宽为特征。在双共振条件（LH频率与快离子的高回旋谐波重合）下，由横向快离子分量驱动的LH不稳定性的理论模型被建立。不稳定性增长率被推导。实验上观察到高体离子温度的稳定化效应，与理论建模一致。提出了一种类似于众所周知的随机离子加热的不稳定性饱和机制。