Transient and Turbulent Fields in Plasmas

目前正在进行有关电流和热脉冲在磁化等离子体中传输的瞬时效应的实验研究，以及关于波动磁场中相干结构的湍流研究。这些过程涉及基本的等离子体性质，这些性质对于理解等离子体中的输运是必不可少的，它们对惯性和磁聚变、脉冲功率以及空间等离子体中的主动实验具有广泛的兴趣。拟议的工作将在具有出色诊断能力的大型受控实验室等离子体中进行。脉冲电流由电极、粒子束施加，并由磁性天线感应。这些电流的传输将通过电磁波，如动力学Alfven波、哨声和束流模式进行研究。热脉冲是利用磁天线的脉冲、强射频场产生的。近无碰撞等离子体中的热输运不能用经典扩散模型来描述，而可能涉及双层和非麦克斯韦分布。使用定向速度分析器、发射电场探头和三维可移动的矢量磁场探头，可以得到场和粒子的详细图像。我们将研究从热水平到环境磁场的磁场湍流。它是由回旋谐频下形成相干射频结构的粒子束中的电流涨落或高β等离子体中的不稳定性(如产生光束的哨声和较低的混合湍流)激发的。利用条件平均这一使用数字示波器的特殊统计技术，可以在湍流场中分辨出相干的磁结构。这些“岛屿”中的场和粒子将被绘制成地图，以便在微观尺度上研究传输过程。将开发完善的等离子体诊断工具和技术。这样详细的实验有望提高对等离子体基本性质的认识，对等离子体的各种用途有应用，并培训学生现代实验等离子体物理。

Experimental research is being pursued on transient effects dealing with the transport of current and heat pulses in magnetized plasmas and turbulence studies dealing with coherent structures in fluctuating magnetic fields. These processes address fundamental plasma properties which are essential for understanding transport in plasmas, and they are of broad interest in inertial and magnetic fusion, pulsed power, and for active experiments in space plasmas. The proposed work will be performed in a large, controlled laboratory plasma with excellent diagnostic capabilities. Pulsed currents are imposed with electrodes, particle beams and induced by magnetic antennas. The transport of these currents by electromagnetic waves such as kinetic Alfven waves, whistlers and beam modes will be studied. Heat pulses are generated with pulsed, intense rf fields of magnetic antennas. The heat transport in nearly collisionless plasmas cannot be described by classical diffusion models but may involve double layers and non- Maxwellian distributions. Using directional velocity analyzers, emissive electric field probes and vector magnetic field probes moveable in 3 dimensions will yield a detailed picture of fields and particles. Magnetic turbulence will be investigated from the thermal level to that of the ambient field. It is excited by current fluctuations in particle beams forming coherent rf structures at cyclotron harmonic frequencies or by instabilities such as beam-generating whistlers and lower hybrid turbulence in high-beta plasmas. Using conditional averaging, a special statistical technique employing digital oscilloscopes, coherent magnetic structure can be resolved in a turbulent field. Fields and particles in such "islands" will be mapped so as to study transport processes on a microscopic scale. Refined plasma diagnostic tools and techniques will be developed. Such detailed experiments are expected to advance the knowledge of basic plasma properties, have i mplications to the various uses of plasmas, and train students in modern experimental plasma physics.