In this paper, we propose an efficient diagnostic technique for determining spatially resolved measurements of the ion density ratio in a magnetized two-ion species plasma. Shear Alfvén waves were injected into a mixed helium–neon plasma using a magnetic loop antenna, for frequencies spanning the ion cyclotron regime. Two distinct propagation bands are observed, bounded by $\omega < \varOmega _\textrm {Ne}$ and $\omega _{ii} < \omega < \varOmega _\textrm {He}$ , where $\omega _{ii}$ is the ion–ion hybrid cutoff frequency and $\varOmega _\textrm {He}$ and $\varOmega _\textrm {Ne}$ are the helium and neon cyclotron frequencies, respectively. A theoretical analysis of the cutoff frequency was performed and shows it to be largely unaffected by kinetic electron effects and collisionality, although it can deviate significantly from $\omega _{{ii}}$ in the presence of warm ions due to ion finite Larmor radius effects. A new diagnostic technique and accompanying algorithm was developed in which the measured parallel wavenumber $k_\parallel$ is numerically fit to the predicted inertial Alfvén wave dispersion in order to resolve the local ion density ratio. A major advantage of this algorithm is that it only requires a measurement of $k_\parallel$ and the background magnetic field in order to be employed. This diagnostic was tested on the Large Plasma Device at UCLA and was successful in yielding radially localized measurements of the ion density ratio.

中文翻译：

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剪切 Alfvén 波在二离子等离子体中的传播及其作为离子密度比诊断的应用

在本文中，我们提出了一种有效的诊断技术，用于确定磁化二离子物种等离子体中离子密度比的空间分辨测量值。使用磁环天线将剪切 Alfvén 波注入到混合氦-氖等离子体中，用于跨越离子回旋加速器的频率。观察到两个不同的传播带，以 $\omega < \varOmega _\textrm {Ne}$ 和 $\omega _{ii} < \omega < \varOmega _\textrm {He}$ ， 在哪里 $\omega _{ii}$ 是离子-离子混合截止频率和 $\varOmega _\textrm {他}$ 和 $\varOmega _\textrm {Ne}$ 分别是氦和氖回旋加速器的频率。对截止频率进行了理论分析，结果表明它在很大程度上不受动力学电子效应和碰撞性的影响，尽管它可能会显着偏离 $\omega _{{ii}}$ 由于离子有限拉莫尔半径效应，在存在暖离子的情况下。开发了一种新的诊断技术和伴随算法，其中测量的平行波数 $k_\平行$ 在数值上拟合预测的惯性 Alfvén 波色散，以解决局部离子密度比。该算法的一个主要优点是它只需要测量 $k_\平行$ 和背景磁场，以便被采用。这种诊断在加州大学洛杉矶分校的大型等离子设备上进行了测试，并成功地产生了离子密度比的径向局部测量。