Tang Introduction to Plasmas and Plasma Dynamics

With Reviews of Applications in Space Propulsion, Magnetic Fusion and Space Physics
1. Auflage 2015
ISBN: 978-0-12-801800-2
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 362 Seiten

Introduction to Plasmas and Plasma Dynamics provides an accessible introduction to the understanding of high temperature, ionized gases necessary to conduct research and develop applications related to plasmas. While standard presentations of introductory material emphasize physics and the theoretical basis of the topics, this text acquaints the reader with the context of the basic information and presents the fundamental knowledge required for advanced work or study. The book relates theory to relevant devices and mechanisms, presenting a clear outline of analysis and mathematical detail; it highlights the significance of the concepts with reviews of recent applications and trends in plasma engineering, including topics of plasma formation and magnetic fusion, plasma thrusters and space propulsion. - Presents the essential principles of plasma dynamics needed for effective research and development work in plasma applications - Emphasizes physical understanding and supporting theoretical foundation with reference to their utilization in devices, mechanisms and phenomena - Covers a range of applications, including energy conversion, space propulsion, magnetic fusion, and space physics

Dr. Hai-Bin Tang is Professor of Aerospace Science and Technology, and Vice Dean of the School of Astronautics at Beihang University, China. His research interests include plasma and fluid physics, electric propulsion and space propulsion systems, numerical modeling, and experimental measurement.

Autoren/Hrsg.

Tang, Hai-Bin

Leseproben

Chapter 1

The Plasma Medium and Plasma Devices

Abstract

This chapter provides an introduction to the existence of ionized gases and plasma in nature and in devices that are in common use and new devices that are being developed. With the exception of our near-Earth environment, ionized gases are common in the universe. The electrical properties of plasma allow utilization in energy transfer and in force applications in unique ways. Plasmas in nature are generally of low pressure and high temperature. Laboratory devices can generate plasmas with low and high pressures and low and high temperatures. Existing devices that utilize plasmas are identified, and some applications that promise future revolutionary developments are discussed.

Keywords

Electric discharges; Fusion; Ionized gases; Magnetosphere; Solar plasma; Space propulsion

Introduction

The world in which we function is consistent with our physical characteristics defined by mass, volume, and energy. Our natural environment is benign—a gaseous atmosphere of nitrogen and oxygen at pressures of 105N/m2, temperatures of 0–40°C, and particle densities of 1025 m-3. We are continuously receiving radiant energy from the Sun at a rate of about 300W/m2, in a 24-h cyclical pattern due to the Earth's rotation, which is modified by the annual cycle of the Earth's orbital motion around the Sun.

In the course of history, we have observed in our local environment exceptional natural displays of energy that demonstrate the existence of forces and energies well beyond our control. The Sun itself is clearly of a very high temperature and is capable of transient, powerful eruptions. Storms in the atmosphere display enormous wind power; electrical lightning strikes generating shock waves and creating local temperatures that can ignite combustion. Polar latitudes evidence dynamic geophysical scale displays of light that inspire awe and require understanding. All these natural events demonstrate and testify to the high-energy excitation of our gaseous atmosphere in response to geophysical electric and magnetic field-based mechanisms. In fact, in the total physical world, with the exception of the near-Earth environment, the medium we exist in is composed of high-energy particles with electric charges, and they are in incessant motion, sometimes directed and sometimes random. In short, the physical universe is largely composed of plasma.

This work is an introduction to the properties and behavior of that electrically active medium and of some of the devices that have been developed to utilize the characteristics of energy and force transfer with the plasma. Plasma is a medium that includes species of charged particles, and plasma dynamics is the description and analysis of force generation and energy transfer with that medium. The important characteristic of gaseous plasmas is their physical makeup, which allows reaction to electric and magnetic fields, particularly and including the conduction of current. There is a conceptual similarity of plasmas with solid electrical conductors whereby flowing electrons and electromagnetic waves move through static ions in response to electric and magnetic fields. The charged plasma particles develop organized (collective) behavior due to interaction with large numbers of nearby charged particles. Due to the energy equilibrium but mass differences of plasma component species, there is the occurrence of local electric field generation, which is the beginning of a complex interplay of particle motion and electric and magnetic fields. These behaviors are the ingredients that allow unique device performance using plasmas.

With our relatively recent discovery (and still developing knowledge) of atomic structure, electrical charges and currents, electric and magnetic fields, and electromagnetic radiation, we have begun the process of defining and controlling particle behavior to develop new devices to serve our needs. Particularly in the last 50years, we have seen the application of such knowledge to create devices with enhanced capability in light and power generation, communications, scientific diagnostics in the physical and biological sciences, and space exploration (National Research Council, 1995). This work introduces the student and researcher to the basic mechanics of the particle interactions inherent in devices that utilize charged particles and presents the framework for understanding their further application in new devices.

Plasmas in Nature

General Description

A general representation of plasmas that are observed in nature is presented in Figure 1.1.

The plasma regions are identified by their properties of particle density and particle temperature.

The Solar Plasma

It can be identified that gases in the solar system occur over the range of 1033p/m3 and 107K in the solar core to 109p/m3 and 105K in the Earth's aurora (Kivelson and Russell, 1993). Both these extremes in properties represent plasmas that have important physical characteristics and if produced in the laboratory can be utilized in practical devices. It can be seen that lightning, which occurs at atmospheric pressure conditions, is typified by temperatures of 10,000K or more.

Figure 1.1 Property domains of plasmas occurring in space and natural environment. Adapted from web site: http://www.cpepphysics.org/fusion_chart_view.html, Contemporary Physics Educ. Project (2010), with permission.

As the solar plasma and its energies are so significant in our environment, it is useful to identify as a reference the orders of magnitude of a set of specific properties and parameters relative to the Earth. The plasma in the interplanetary system originates from the Sun. The Sun has a mass of 2×1030kg, diameter of 1.4×106km, and a composition of 75% hydrogen and 25% helium. The thermonuclear fusion of hydrogen to helium produces a core temperature of 1.6×107K and a corona temperature of 5×106K. This plasma of the Sun escapes in all directions and expands into all regions of the solar system. At the Earth radius from the Sun the particle proton and electron densities are about 10 cm-3, with proton temperature of 4×104K and electron temperature of 1.5×105K, and most importantly a solar wind flow speed of about 400m/s. The interaction of this flowing plasma with the Earth's magnetic field produces the hypersonic flow field of the asymmetric magnetosphere (Bothmer, 1999), as shown in Figure 1.2.

Plasmas in Laboratory/Device Applications

General Description

Because of the potential for application in new revolutionary devices that can extend our capabilities in a number of technologies (Charles, 2009), the behavior of ionized gas plasmas has been explored over a broad range of densities and temperatures, steady state and transient conditions, small and large size scales, power levels and sources, and geometries. Laboratory devices have been constructed for basic scientific research studies (McCracken and Stott, 2005) and as test beds for product development (Cappitelli and Gorse, 1992). As with any new technology, the identification of operating principle is basic and the definition of scalability of the principle is critical to expand the operating range. A schematic display of some of the general types of plasma devices that have been developed are presented in Figure 1.3. General indications of plasma length scales are shown with respect to plasma charge separation (upper left), particle mean free path (?), and geophysical size (lower right).

Figure 1.2 Schematic of the solar plasma and the Earth's magnetosphere structure. Adapted from European Space Agency, ESA (2006) with permission.

Figure 1.3 Schematic of plasma density and temperature in various types of plasma devices. Adapted from Sheffield (1975). Plasma Scattering of Electromagnetic Radiation. Academic, New York.

Categories of Device Plasmas

There are a number of ways to classify the different types of devices that generate and utilize the unique characteristics of plasmas. Historically, devices for generating light were most basic, and fluorescent discharge tubes have been in use for over 100years. Gas discharge vacuum tubes (Cobine, 1957) for voltage and signal modification in communication devices enabled advances that changed society. However, perhaps the most effective criteria for classifying devices are that shown in Figure 1.3: the density and temperature...