Introduction

A fully ionized plasma is a collection of a large number of negatively charged electrons and positively charged ions with an insignificant amount of neutral atoms. Plasmas by nature are hot. A suitable container is the first and the foremost need of a plasma-based process. Clearly no material vessel can hold, say, a million degree plasma. We have learnt in chapter one that the cosmos abounds in such hot and even hotter plasmas. The nature holds plasmas predominantly by the force of gravity and by the force of magnetism. In rare circumstances plasmas could also be trapped by the force of the electromagnetic radiation. In this chapter we shall discuss different methods of plasma confinement.

The Grip of Gravity

It is a common experience that in order to rotate a stone tied to one end of a string, one has to pull the other end of the string toward oneself for if one does not, the stone with the string would fly off. The necessary inward pull is called the centripetal force, i.e., it acts toward the center around which the object is rotating. The opposite of the centripetal force is the centrifugal force due to which a rotating object has a tendency to fly off if not pulled in sufficiently. The Earth revolves around the sun, the sun pulls it toward itself. The centripetal force, here, is the gravitational pull of the sun that keeps the Earth in its orbit.