Introduction to Plasma Physics

Gerard Belmont, Laurence Rezeau, Caterina Riconda, Arnaud Zaslavsky

• Publisher: ISTE Press - Elsevier
• Year: 2019
• Print ISBN: 9781785483066
• eBook ISBN: 9780128189788
• Topic: Physical Sciences
• Subtopic: Meteorology & Climatology

Introduction to Plasma Physics presents the latest on plasma physics. Although plasmas are not very present in our immediate environment, there are still universal phenomena that we encounter, i.e., electric shocks and galactic jets. This book presents, in parallel, the basics of plasma theory and a number of applications to laboratory plasmas or natural plasmas. It provides a fresh look at concepts already addressed in other disciplines, such as pressure and temperature. In addition, the information provided helps us understand the links between fluid theories, such as MHD and the kinetic theory of these media, especially in wave propagation. - Presents the different phenomena that make up plasma physics - Explains the basics of plasma theory - Helps readers comprehend the various concepts related to plasmas

1

What Is Plasma?

Abstract

The plasmas, which will be presented in this chapter, resemble gases, but because they are constituted of free charged particles, the physics that govern their dynamics is radically different. First, the charged particles' motion is determined by electromagnetic fields, and second, the fields are created by charge and current densities caused by these particles. This coupling will be illustrated in a simple example, called "plasma oscillation". In this fundamental example, we will see how all field fluctuations are accompanied by matter movements and, vice versa, how every matter movement is accompanied by a field fluctuation.

Keywords

Coupled system resolution; Electric discharges; Electron response time; Nuclear fusion; Plasma oscillation; Plasma physics; Quantum effects; Radiation absorption; Velocity distribution function

The plasmas, which will be presented in this chapter, resemble gases, but because they are constituted of free charged particles, the physics that govern their dynamics is radically different. First, the charged particles’ motion is determined by electromagnetic fields, and second, the fields are created by charge and current densities caused by these particles. This coupling will be illustrated in a simple example, called “plasma oscillation”. In this fundamental example, we will see how all field fluctuations are accompanied by matter movements and, vice versa, how every matter movement is accompanied by a field fluctuation.

1.1 Under what conditions is matter in the plasma state?

The term “plasma” was introduced for the first time by I. Langmuir in 1928 when he studied the ionized gas behavior in discharge tubes because the ion oscillations observed in these tubes were reminiscent of the oscillations observed in a gelatinous environment (plasma means gelatinous matter, or matter that can be modeled, in Greek). Plasma then appears as a “fourth” state of matter, a gaseous and ionized medium in which particle dynamics is dominated by electromagnetic forces: other forces, such as gravity, are often negligible in this kind of system. Neutral media are, in fact, also made up of electrons and protons, which are charged particles; however, in this type of medium, they are bound within globally neutral atoms and molecules. What distinguishes plasma from neutral media is the presence of “free” charged particles, that is, particles that can move independently (in opposite directions according to the sign of their charge), thus creating currents and deviations from neutrality. The term “plasma” may in fact be extended to all media (equivalents of gases, as well as liquids and solids) in which there are such free charged particles. We will limit ourselves in this book essentially to plasmas, which are the equivalents of gases and which must be named, more precisely, “weakly correlated plasmas“. We will therefore consider media that are sufficiently tenuous.

The development of plasma physics followed these first discoveries, in conjunction with research on radio-communications. As early as 1901, G. Marconi observed the reflection of the waves on what he thought was the atmosphere, but it was in fact the ionosphere. The idea that our atmosphere is ionized from a certain altitude was brought up by E. Appleton in 1925; he thus launched the study of natural plasmas, which has gradually become that of astrophysical plasmas. In the laboratory, studies have continued beyond discharges, particularly with research on electron beams as sources of coherent radiation (klystrons), and they have progressed to a much more intensive stage with the initiation of research on controlled nuclear fusion, circa 1955. More recently, work has been undertaken to study the interactions between plasmas and surfaces, leading to surface treatments in mechanics or microelectronics thanks to plasmas. It has also been shown that laser-created plasmas can behave as sources of rapid particles or radiation, that is, as miniature accelerators, which offer an alternative to traditional accelerators. Plasma research is therefore very active in the fields of astrophysics, fusion and industrial applications.

Under the “normal” temperature and pressure conditions in which we live, particles are naturally bound in the form of neutral atoms and molecules (although, in the rest of the universe, this “fourth” state of matter is the normal state). To create plasma from such a neutral gas, it is necessary to provide energy to remove one or more electrons from each atom. It is therefore necessary that sufficient energy be provided to the atoms so that they are partially, or even totally, ionized. This energy can be p...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Introduction
• 1: What Is Plasma?
• 2: Individual Trajectories in an Electromagnetic Field
• 3: Kinetic Theory of Plasma
• 4: Plasma Fluid Modeling and MHD Limit
• 5: Waves in Plasmas in the Fluid Approximation
• 6: Kinetic Effects: Landau Damping
• 7: Shockwaves and Discontinuities
• References
• Index