"To Tame the Stars"
Fritz Houtermans, the German physicist who discovered that thermonuclear fusion fuels the stars, looked into the starry sky with his female partner just a day after he had made his discovery.
– Don’t they shine beautifully? – she asked.
– Yes – replied Fritz – and I’m the only person in the world who knows why.
More than 80 years after Houtermans’ discoveries there are physicists in the world who not only know the ways of the stars, but they have been making attempts to tame them in laboratories. I am lucky to be one of them. Let me start from the beginning, though.
Thermonuclear fusion, the most powerful reaction discovered by scientists makes the Sun and all the other stars shine and radiate immense quantities of energy. The conditions inside them are close to unimaginable for us. The molecules pressed together by gravitation and heated up to several million Celsius centigrade get into nuclear reactions, which in turn creates chemical elements and lots of energy. The mass-energy relationship according to Albert Einstein is expressed in the following equation:
E = mc2
Every second the sun radiates the amount of energy equal to that of billions of atomic bombs!
One can read this equation like this: energy is emitted due to the newly created molecule’s lower mass than of its ingredients.
Inside the Sun every 1.000 g of hydrogen is transformed into 973 g of helium, which causes ”our star” every second to radiate the amount of energy equal to that of billions of atomic bombs!
The Earth receives only a tiny chunk of the energy, but even that little has been enough to enable life on the planet to flourish in its innumerable variations. This has created so many forms of life that absorb the necessary energy from the Sun. Photosynthesis, fossil fuels, even wind farms in fact are based on the Sun’s energy processed in different ways.
Would it not be easier if we could make such a star here for us to use as we see fit?
This has already been happening. In several laboratories all over the world, e.g. in Japan, China, Russia, India, Europe and the US the scientists have been trying to tame the thermonuclear fusion.
In a star it is the forces of gravitation that work to press it hard enough to unchain the thermonuclear fusion. Then the matter enters its fourth state, plasma, where the electrically charged molecules create an electromagnetic field. We would not be able to achieve this here on Earth, therefore we try something else instead.
We build huge magnets with fields thousands of times stronger than the Earth’s that allow us to harness molecules and turn them into plasma. Through heating it to 100 million degrees we evoke thermonuclear fusion. Deuterium and tritium, isotopes of hydrogen, collide making so much energy that 250 kilograms of thermonuclear fuel equals 3 million tonnes of coal.
This does not bring us slag heaps, radioactive waste or greenhouse gas emissions. Moreover, there is a lot of deuterium in oceanic waters and we can get tritium from lithium that is a common ingredient of rocks. Two bottles of water and three middle-sized stones contain enough deuterium and tritium to produce a sufficient quantity of energy for yearly needs of a household. Then why has it not started yet?!
250 kilograms of thermonuclear fuel = 3 million tonnes of coal
There are a few reasons for that, yet it seems we will be able to tackle them in the forthcoming 20-30 years. Whereas the experiments made so far allowed to cause discharges lasting up to a few dozen seconds, the thermonuclear power plant must work non-stop. Unlike in nuclear power plants, there is no chain reaction there and it is so delicate that it needs lots of effort and knowledge to sustain the whole process. The discharge must be completely isolated, firmly closed in the chamber. But how to prevent the superhot plasma from destroying the chamber’s walls? The next generation of reactors should give us the answer.
ITER (International Thermonuclear Experimental Reactor, but also a Latin word for ”road”), an experimental complex currently being built in the south of France for ca 15 billion euros is a truly international enterprise. EU, China, Russia, Japan, India, South Korea and the US take part in its creation. The ITER will be the first experiment with greater energy gain than loss from thermonuclear fusion. This will allow scientists to observe behaviours of the plasma that provides itself all the energy necessary for its maintenance. It will be the first time in history for conditions comparable with the stars to be created on Earth.
As soon as in 2015, at the Baltic sea will be launched Wendelstein 7-X, an experiment on a slightly smaller scale yet of similar importance as the ITER. There will be plasmas in Greifswald in which conditions for thermonuclear fusion will be sustained. 30-minute discharges with temperatures reaching 100 million degrees will let us learn how to deal with a future thermonuclear power plant.
The Wendelstein 7-X is the first experiment on such a scale that is not going to need electric current flowing through plasma. All the electromagnetic field will be generated in conductors in fantasy shapes immersed in liquid helium.
The 21st century technological extravagance and engineering challenge, one of those that we have managed to beat at Greifswald: how to decrease the temperature from 100 million Celsius centigrade to almost absolute zero where helium goes liquid. What is important, since we had to electrify the plasma, the discharge there lasted below a minute, whereas in Wendelstein 7-X it will reach half an hour. Owing to the answers brought by the experiments ITER in Cadarache and Wendelstein 7-X in Greifswald we are likely within 30 years to build the first thermonuclear power plant and thus to start the new era in the history of mankind. The latter will no longer have to fight for oil and gas – we will have enough for millions of years to come.
Well, maybe then some scientist, today still a toddler, asked about the stars shining beautifully, will reply:
– I tamed one here today.