Introduction

Abstract

The three states of matter, solid, liquid and gas, are well-known to us. As the temperature is elevated, solid is liquefied and liquid is evaporated to form a gaseous state. If we further increase the temperature, the molecules constituting the gas are decomposed into atoms and the atoms are then decomposed into electrons and positively charged ions. The degree of ionization increases as the temperature rises. For the case of hydrogen gas at normal pressure, the ionization becomes almost complete at about (2 ~ 3) × 10⁴K. The ionized gas formed in this way is called high-temperature plasma. It consists of a large number of negatively charged light electrons and positively charged heavy ions, both electrons and ions moving with high speed corresponding to high temperature. The net negative charge of the electrons cancels the net positive charge of the ions in the plasma. This is called the overall charge neutrality of the plasma.