The dense plasma focus is a plasma discharge powered by a capacitor bank. Standard diagnostics include the measurement of the time derivative of the current through and the voltage across its connections with the capacitor bank. Interpretation of this diagnostic data often involves some assumptions regarding the representation of the dense plasma focus as a time varying inductance. One of the characteristic features of the current derivative waveform is a relatively sharp dip and an associated sharp voltage spike. This has often been interpreted as a result of a rapid rise in the time varying inductance of the plasma. Sometimes, an anomalous plasma impedance is invoked. This Letter discusses instances where such interpretation creates conceptual difficulties. A first principles approach to the representation of the dense plasma focus as a circuit element reveals some fundamental problems with the traditional representation of plasma focus as a time varying inductance. The anomalous impedance is shown to be necessary to account for the difference in the motional impedance implied by a time-varying inductance in the circuit element representation and a first principles description based on Poynting's theorem. Dynamo effects that convert post-stagnation local motion of plasma into three-dimensional magnetic fields are shown to contribute to the effective inductance of the plasma focus and resolve the observed conceptual difficulties.

中文翻译：

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关于密集等离子体焦点作为电路元件的表示

密集的等离子体焦点是由电容器组提供动力的等离子体放电。标准诊断包括测量通过的电流的时间导数以及其与电容器组的连接两端的电压。对该诊断数据的解释通常涉及一些关于将密集的等离子体焦点表示为随时间变化的电感的假设。电流导数波形的特征之一是相对急剧的下降和相关的急剧的电压尖峰。这通常被解释为是等离子体随时间变化的电感快速上升的结果。有时会引起异常的等离子体阻抗。这封信讨论了这种解释在概念上造成困难的例子。将密集等离子体焦点表示为电路元件的第一原理方法揭示了传统等离子体焦点表示为时变电感的一些基本问题。示出了异常阻抗对于解决由电路元件表示中的时变电感和基于波因廷定理的第一原理描述所隐含的运动阻抗中的差异是必要的。示出了将等离子体的停滞后局部运动转换成三维磁场的发电机效应有助于等离子体聚焦的有效电感并解决了观察到的概念上的困难。示出了异常阻抗对于解决由电路元件表示中的时变电感和基于波因廷定理的第一原理描述所隐含的运动阻抗中的差异是必要的。示出了将等离子体的停滞后局部运动转换成三维磁场的发电机效应有助于等离子体聚焦的有效电感并解决了观察到的概念上的困难。示出了异常阻抗对于解决由电路元件表示中的时变电感和基于波因廷定理的第一原理描述所隐含的运动阻抗中的差异是必要的。示出了将等离子体的停滞后局部运动转换成三维磁场的发电机效应有助于等离子体聚焦的有效电感并解决了观察到的概念上的困难。