A terrella developed for the undergraduate Advanced Laboratory course in the University of Wisconsin-Madison Physics Department is described. Our terrella consists of a permanent magnet, mounted on a pedestal in a vacuum chamber, surrounded by electrodes that may be biased in various ways. The system can confine a plasma, which may, in some ways, be considered as a toy model of the plasma confined in the Earth's magnetosphere. Our axisymmetric plasma forms in a region where the magnitude of the magnetic field B is 14 G ≤ B ≤ 550 G; for typical operation, the neutral gas pressure is p ∼ 10 − 4 Torr. The plasma is created by thermionic emission from a hot filament. Available diagnostics are a swept Langmuir probe, a spectroscopic fiber and visible-wavelength spectrometer, and visible imaging. In two four-hour laboratory sessions, students are guided through vacuum pumpdown, connection of electrical circuits, establishment of plasma, acquisition of data, analysis of data, and critique of data. In this paper, we present student measurements of radial profiles of electron temperature Te and density ne as well as imaging of mirror trapping and ∇ B drift and curvature drift. We conclude by outlining some opportunities for additional terrella-based student experiments.

中文翻译：

---

Terrella 高级本科实验室

描述了为威斯康星大学麦迪逊分校物理系本科高级实验室课程开发的 terrella。我们的 terrella 由永久磁铁组成，安装在真空室的基座上，周围环绕着可能以各种方式偏置的电极。该系统可以限制等离子体，在某些方面，它可以被视为限制在地球磁层中的等离子体的玩具模型。我们的轴对称等离子体形成于磁场 B 的大小为 14 G ≤ B ≤ 550 G 的区域；对于典型操作，中性气体压力为 p ∼ 10 − 4 Torr。等离子体是由热灯丝的热电子发射产生的。可用的诊断包括扫描朗缪尔探头、光谱光纤和可见光波长光谱仪以及可见光成像。在两个四小时的实验室课程中，引导学生完成真空抽真空、电路连接、等离子体建立、数据采集、数据分析和数据评论。在本文中，我们展示了学生对电子温度 Te 和密度 ne 的径向分布的测量以及反射镜俘获和 ∇ B 漂移和曲率漂移的成像。最后，我们概述了一些额外的基于 terrella 的学生实验的机会。