Nuclear fusion will be the only energy source soon. On its development depends the future of our children. Will they live in world of wars for oil or in world of surplus of cheap energy?

Fusion reactors

Fusion reaction of two deuterons into helium-3 and neutron

How to construct fusion reactor is the problem number one of nuclear fusion. Initiation of fusion is easy. You can start your own little fusion at home. You would need only electric transformer, candle (as source of ionized gas) and a glass of water. Place glass and candle's flame between electrodes connected to transformer. Fusion begins. However fusion proceeds, it can't generate meaningful amount of energy, because only low percentage of ionized atoms hit hydrogen in water required speed.

This is why we have to look for more complicated ways to start nuclear fusion and build complex systems like tokamaks. Tokamaks are most common system to make fusion get started.

Tokamak's function

The inside of tokamak
Look into tokamak reactor
Credit: EFDA-JET

Tokamak is toroidal vacuum chamber with plasma ring in its centre. Chamber forms field coil and conductive fully ionized plasma short circuit. Alternating current in coil induces in plasma high current at low voltage, thereby temperature rises. The lowest temperature we need to initiate fusion is a few tens (sometimes up to hundreds) million centigrades, thus is necessary to encage plasma in magnetic field of coil. There is no material in the world that could sustain this incredible temperature. Now we know how to gain energy from fusion. But what we have to do with it?

From energy to electricity

How to transform energy to electricity? Is possible to use common way via steam turbines connected to generator. Heat from fusion reactor vaporizes water and steam actuates turbine, thereby generator. This way is common but not much efficient (totally about 20 %). So we are trying to find another. There were experiments that shown is possible to direct convert energy of charged particles into electricity. Conversion efficiency should be up to 80 % but construction of converter would be more complex and expensive. We don't know how will the first fusion power plant gain electricity (I guess via steam turbine). We have enough time to thinking, because construction of first power plant is planned to 2045.

Today's and near future's fusion tokamaks

International fusion reactor will be done soonest in late 2016 and full performance reach in 2022. It will be the most perspective and advanced reactor in near future.
Joint European Torus - Record tokamak, produced fusion power of 16 MW, ratio of energy gained to energy consumed was 0.7.
Japanese Tokamak
Experimental Advanced Superconducting Tokamak in Hefei, China, start is planned for July/August 2006
Mega Ampere Spherical Tokamak - Successor of START, Culham, United Kingdom, special construction tokamak
Alcator C-Mod
Tokamak in MIT, Cambridge, USA

For more information see references