Research on collapse of double layers and turbulent-heating phenomena

1.利用红宝石激光汤姆逊散射测量了线性湍流加热装置中产生的双层(DL)从形成到崩塌过程中电子温度T的时间演化。在DL的形成过程中观察到一个电子空穴。T的增加也伴随着电子空穴的衰变，而电子空穴的衰变反过来又导致离子声波的激发，从而导致DL.2的形成。考察了可能影响DL寿命的参数。研究发现，电极间距和中性粒子的分压对DL的寿命有很大影响，而与所用材料和壁厚的关系不大。在边界条件与实验条件接近的情况下进行了计算机模拟。实验结果与数值模拟结果在定性上符合得很好。在上述实验和模拟结果的基础上，提出了一个理论模型来解释线性湍流加热装置中导致DL崩塌的物理过程。该模型考虑了由离子输运引起的阴阳极侧等离子体密度的不平衡。由此产生的压力不平衡将DL推向阳极。然后，当到达阳极时，DL消失。在适当的条件下对所提出的模型进行了进一步的实验和仿真，得到了合理的结果。本研究中得到的关于下垂的物理图像与下垂的内部结构的变化有关，而不是由于外部环路而引起的常规机制的改变，并且可以应用于其他的下沉，如极光中的下沉。

1. Temporal evolution of electron temperature T. was measured during the period from formation to collapse of double layers (DL) produced in a linear turbulent-heating device, by making use of Ruby laser Thomson scattering. An electron hole was observed berofe the formation of DL. An increase in T. was also observed concomitant with decay of the electron hole,which, in turn, resulted in excitation of ion acoustic waves leading to formation of DL.2. Parameters which may have effect on the life time of DL were examined. It was found that the life time of DL depends strongly on the distance between two electrodes and partial pressure of neutral particles but less on materials used and size of the wall.3. Computer simulation were carried out with boundary conditions close to the experimental ones. Qualitatively good agreement was obtained between experimental and simulation results for the formation process of DLs.4. Based on the experimental and simulation results decribed above, a theortical model was proposed to understand physical process leading to collapse of DL in the linear turbulent=heating device. The model takes into account the inbalance of plasma densities in the anode and cathode sides seen from the DL, which may be brought forth by "the ion transport" through the DL. The pressure inbalance so produced pushes the DL toward the anode. Then the DL vanishes when it reaches the anode.5. Additional experiments and simulations were carried out under the condition appropriate to verify the proposed model, and reasonable results were obtained.6. The physical picture obtained in the present research as to the collapse of DL is related to change in internal structure of DL, as opposed to conventional mechanism due to external cicuit, and may be applied to other DLs such as those in aurora.