The fuel has to be millions of degrees centigrade for fusion to occur. As we know, hot material expands and cools, so the atoms in the fuel become so far apart that the probability of interaction is tiny.


The Sun

For fusion to work as an energy source one must confine the plasma. The sun uses its own mass to confine itself via its gravitational field. No vessel could contain such material without either:

  1. turning into plasma or
  2. cooling down the fuel to point where fusion no longer occurs.

The two major concepts currently being studied are:

  1. To confine the plasma with magnetic and electric fields so that there is no contact with vessel walls. This works on the principle of confining the plasma for long enough periods that the particles will interact with each other. This is known as magnetic confinement fusion. An international facility called ITER, to be built in France, is expected to demonstrate this.
  2. To confine the plasma using inertia of the fuel. This involves compressing a tiny pellet of Deuterium-Tritium fuel (with lasers or radiation) to high density for a short period of time. Raising the fuel to high densities forces more particles to interact with each other that at solid density. This method is known as inertial confinement fusion. HiPER is expected to demonstrate this principle.