A DC discharge plasma experiment for undergraduate laboratories

TL;DR

This paper describes the design and implementation of a DC glow-discharge plasma chamber for undergraduate labs, enabling hands-on exploration of plasma phenomena like breakdown, electron temperature, and magnetic focusing.

Contribution

It introduces a versatile, student-built plasma chamber with comprehensive diagnostics, facilitating fundamental plasma experiments in undergraduate education.

Findings

Characterized Paschen breakdown relation

Mapped electron temperature and density distributions

Demonstrated magnetic focusing of electrons

Abstract

Plasma physics offers a wide range of fundamental phenomena, making it an excellent subject for undergraduate laboratory instruction. In this work, we present the design, construction, and characterization of a DC glow-discharge plasma chamber developed for the junior-level curriculum, a project carried out by two undergraduate students. The apparatus consists of a 1-meter-long quartz tube with a movable electrode, enabling systematic exploration of plasma behavior under varying pressure, voltage, and geometry. Using this platform, we characterized the Paschen breakdown relation and the voltage-current characteristics of the plasma. We then developed Langmuir probes to map spatial distributions of electron temperature and density, and used Boltzmann plot spectroscopy to measure excitation temperatures across different plasma regions. Finally, with custom Helmholtz coils, we demonstrated magnetic focusing of electrons. We performed Runge-Kutta simulations of particle trajectories and analyzed the electron drift velocity by comparing the focal lengths. Overall, this plasma chamber provides a versatile platform for investigating fundamental plasma phenomena and offers potential for future studies, including microwave-plasma interactions and other student-driven investigations.