An experiment in a linear device, the Large Plasma Device, is used to study sheaths caused by an actively powered radio frequency (rf) antenna. The rf antenna used in the experiment consists of a single current strap recessed inside a copper box enclosure without a Faraday screen. A large increase in the plasma potential was observed along magnetic field lines that connect to the antenna limiter. The electric field from the spatial variation of the rectified plasma potential generated $\overrightarrow{\mathit{E}}\times {\overrightarrow{\mathit{B}}}_0$ flows, often referred to as convective cells. The presence of the flows generated by these potentials is confirmed by Mach probes. The observed convective cell flows are seen to cause the plasma in front of the antenna to flow away and cause a density modification near the antenna edge. These can cause hot spots and damage to the antenna and can result in a decrease in the ion cyclotron range of frequencies antenna coupling.

中文翻译：

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大型等离子设备中快速波天线对流细胞形成的实验观察

线性设备大型等离子体设备中的一项实验用于研究由有源供电的射频（rf）天线引起的护套。实验中使用的RF天线由一个单电流带组成，该单电流带凹入在没有法拉第屏蔽的铜箱外壳内。沿着连接到天线限制器的磁场线观察到等离子体电势大大增加。电场是由整流等离子体势的空间变化产生的$\overrightarrow{\mathit{E}}\times {\overrightarrow{\mathit{乙}}}_0$流，通常称为对流池。由马赫探针证实了由这些电势产生的流动的存在。观察到的对流单元流动可导致天线前面的等离子体流走，并在天线边缘附近引起密度变化。这些会引起热点并损坏天线，并会导致天线耦合的离子回旋加速器频率范围减小。