heavier forms of hydrogen, known as deuterium (with one proton and one neutron) and tritium (one proton plus two neutrons) are fused.

engineers need to build the reactor to withstand temperatures at least ten times that of the Sun – which means hundreds of millions of degrees.

physicists have designed a doughnut-shaped reaction chamber, called a tokamak.

okamak deploys a powerful magnetic field to suspend and compress the hydrogen plasma

the fusion reaction is not self perpetuating.

he reaction far safer.

one of the hydrogen isotopes used, tritium, is radioactive

moderately seismically active

he site won't be ready for the first experiments until 2020.

deuterium (a hydrogen isotope abundant in sea water) and tritium (which will be made from lithium), won't take place until 2028.

The plan is to use 50 megawatts (in heating the plasma and cooling the reactor), and get 500 MW out.

1997, achieved a 16 MW output with a 25 MW input.

If Iter is successful in its proof of principle mission, the first demonstration fusion plants will be built,

the technology remains unproven,

92 powerful lasers to crush a minuscule amount of fuel so hard and fast that it becomes hotter than the sun.

The lasers are fired into a gold capsule that holds a 2mm-wide spherical pellet.

The fuel is coated on the inside of this plastic pellet in a layer as thin as a human hair.

When the laser light enters the gold capsule, it makes the walls of the gold container emit x-rays, which heat the pellet and make it implode with extraordinary ferocity. The fuel, a mixture of hydrogen isotopes called tritium and deuterium, partially fuses under the intense conditions.