Caviton Induced Double Layr-Like Potential Structures in Plasmas

在高功率微波-等离子体系统中，实验研究了在强局域电子等离子体振荡产生的密度腔--空穴--处产生双层势结构的新机制.空穴子是被俘获在密度空腔内的局部化电子等离子体波，其由与局部化波本身相关联的有质动力产生。人们已经知道，空穴在处于强朗缪尔束缚态的等离子体中起着重要的作用.利用短脉冲微波（f=3GHz，峰值功率= 60 kW，脉宽~ 1 μ s）的共振吸收，在非均匀等离子体中产生了空穴子。已经发现，在共振层r（n-10^ cm^）处，可以产生与空穴的形成相关联的双层状势结构<11><-3>。当空穴形成时，在空穴的位置处出现负势阱。研究发现，这种势阱排斥背景电子，导致低电位区的膨胀，发展成双层状的势阱结构.离子分布函数的测量表明，在上述过程中产生的离子相空间空穴。数据表明，离子相空间孔的位置附近的空穴产生的空穴，并在约离子声速移动。这种离子相空间空穴的作用将在我们未来的实验中进一步研究。在注入微波束后，空穴诱导双层势结构的高低势区之间的电势差在-0.5 μ s处达到饱和，其值与入射微波脉冲的峰值功率成正比.一维粒子模拟的结果与我们的实验结果是一致的。进一步的模拟工作正在进行中。

A new mechanism for generating double layr-like potential structures at the location of a density cavity created by intense, localized electron plasma oscillation--caviton-- is experimentally investigated in a high-power microwave-plasma system.1. Cavitons are localized electron plasma waves trapped inside density cavities which are generated by the ponderomotive forces associated with the localized waves themselves. It has been known that cavitons play an important role in plasmas which are in the state of strong Langmuir turbulence.2. In this investigation, cavitons are created in an inhomogeneous plasma by utilizing the resonance absorption of a short microwave pulse (f=3GHz, peak power=60kW,pulse duration-1 mus). It has been found that a double layr-like potential structure can be generated associated with the formation of a caviton at the resonance layr (n-10^<11>cm^<-3>).3. As the caviton is formed, a negative potential well appears at the location of the caviton. It has been found that this potential dip repels background electrons, causing the expansion of the low potential region to develop into a double layr-like potential structure.4. The measurements of the ion distribution function suggest that an ion phase-space hole is generated during the above process. Data indicate that the ion phase-space hole is created near the location of the caviton and moves at approximately the ion acoustic speed. The role of this ion phase-space hole will be examined further in our future experiments.5. The potential difference between the high and low potential regions of the caviton induced double layr-like potential structure saturates at-0.5 mus after the injection of the microwave beam, and it's value is proportional to the peak power of the incident microwave pulse.6. The results of one-dimensional particle-in-cell computer simulations are consistent with our experimental results. Further simulation work is under way.