It has been less than two weeks since physicists at the Laurence Livermore National Laboratory in California announced a major advance towards fusing atomic nuclei using laser bombardment.

This so-called inertial fusion is one of the two main approaches being pursued in order to use nuclear fusion to generate energy.

Nuclear fusion processes make the sun and most stars shine.

If they could be mastered technically on earth, we would have a clean, climate-neutral and practically inexhaustible source of energy.

Ulf von Rauchhaupt

Editor in the “Science” section of the Frankfurter Allgemeine Sunday newspaper.

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This afternoon, the other approach to achieving this goal had its moment of glory: nuclear fusion by so-called magnetic confinement.

Scientists at the European experimental reactor JET (Joint European Torus) at Culham, in the English county of Oxfordshire, presented results from experiments conducted last year that they had been working towards for more than a decade.

In their reactor, they managed to ignite a self-sustaining fusion reaction that produced a total of 59 megajoules of energy for around five seconds.

JET broke its own record from 1997, when 22 megajoules of fusion energy were released in five seconds.

Now 59 megajoules is the energy content of about 1.7 liters of gasoline.

But they were released by fusion reactions in a fuel quantity of only 200 micrograms of a mixture of the hydrogen isotopes deuterium and tritium - also called heavy or super-heavy hydrogen.

In terms of fuel quantity, the fusion of deuterium and tritium into helium is more than six million times more productive than burning natural gas and more than four million times than fission of enriched uranium, according to the Eurofusion consortium, which coordinates JET's scientific program.

And yet this new success in fusion research is still a long way from anything that could be used to operate an economic power plant.

Because the 59 megajoules within five seconds - i.e. a generated power of roughly 10 megawatts - only came out because the hydrogen isotopes were present as a plasma with a temperature of more than one hundred million degrees - the temperature in the core of the sun is just 15.6 million Degree.

In order to heat the fuel in this way, 33 megawatts of heat output were required.

The ratio of energy generated and energy put into it, the so-called Q-plasma value, was a little over 0.3 and therefore less than one.

The Q value thing

In order to assess how close a fusion experiment is to a power plant, however, the energy produced must be compared to the total energy expended.

Then not only the heat energy has to be considered, but also the operation of the huge magnetic coils, whose fields keep the plasma away from the inner walls of the reactor vessel - up to the energy expenditure for the separation of the heavy water from normal water.

This ratio, the actual Q value, is not always useful to estimate in scientific fusion experiments, but it is still at least one order of magnitude below the Q plasma value.

According to the Eurofusion consortium, with a "break even", i.e. a fusion reactor that actually produces more energy than needs to be put into it,