Study of the strong electrostatic fields leaved after an interaction between an intense electron beam and plasma

朗缪尔波在大振幅时变得不稳定，并可能产生大量局域的朗缪尔波波包，称为空穴。在强朗缪尔湍流理论中，对其非线性特性进行了深入的研究。一般来说，电场的测量是困难的，理论预测的空穴的三维结构也不能很好地揭示出来。本研究的目的就是利用电子束探测技术来研究这种湍流场。众所周知，这种诊断是一种根据探测光束轨迹的偏转测量未知电场的方法。通常使用聚焦良好的平行光束来实现这一目的，我们在以前的实验中使用了这种类型的光束。我们的研究显示了这种方法的困难，因为观测到的偏转不能仅仅归因于空穴场，而是其他机制。在那里留下了大量的模棱两可的东西。首先，技术问题，即Deg…更多的数据质量问题，都得到了解决。它使探测密度低得多的探测光束成为可能，提高了测量的可靠性，并提供了另一种可能性。其次，尝试了一种使用电子束的阴影技术。这是首次将该技术应用于诊断的报道。大直径探测梁的使用使探测挠度的特殊分布成为可能。在束流图形图像中发现了许多气泡。很明显，我们的等离子体中存在一个复杂的场，就像湍流理论所预期的那样。平均大小随等离子体密度的变化而变化，实验中估计的平均大小约为德拜长度的20倍。另一方面，理论研究指出，偏转角只有在空穴崩塌的最后阶段才变得突出。可以解释为什么在实验中观察到了小的空洞，尽管湍流理论说，大小的空穴的数量预计会更高。较少

Langmuir wave becomes unstable at the large amplitude, and possibly produces a number of localized wave packets of Langmuir wave, which is called a caviton. The nonlinear properties are investigated strongly in the theory of the strong Langmuir turbulent. Generally, measurements of the electric field is difficult, and the 3-dimensional structure of the caviton which is predicted from the theory is not revealed well. The purpose of this research is to study such turbulence field using electron-beam probing-technique. The diagnosis is well known as a method to measure un-known electric field from deflection of the trajectory of a probing beam. Usually a well-focused parallel beam is used for this purpose, and we employed this type of beam for previous experiments. Our study showed difficulties of the method, because the observed deflections could not be attributed only to the caviton fields but other mechanisms. Large ambiguities were left there.At first, the technical problems, that deg … More rade the quality of the data, are solved. It makes possible to detect a probing beam that has much lower density, and raise the reliability of the measurement, and give another possibility. Second, a shadowgraph technique using an electron beam is tried. This is first report to apply the technique for diagnostic. An employment of a large diameter probing-beam makes it possible to detect the special distribution of the deflection. Many bubbles were found in the beam pattern images. It is apparent that a sophisticated field, which is like the one expected from the turbulent theory, exists in our plasma. The averaged size of babbles is change by the plasma density and is estimated about 20 times of the Debye-length in the experiment. On the other side, a theoretical investigation pointed out the fact that the deflection angle becomes prominent only when the cavitons are at final stage of the collapse. It is possible to explain why the small babbles are observed in the experiment, though the turbulent theory says the population of the caviton with larger size is expected to be higher. Less