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What is behind me
is the powerhouse of the Universe.

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It is just a conventional star.

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It is our Sun.

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And this power station
has been running for billions of years,

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reliably delivering energy to us
and to the rest of the Universe

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just by light emission.

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So, that's a very nice thing,
and it obviously runs,

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and the mechanism
through which it runs is fusion,

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and I'm going to explain to you
something about that.

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But I will also ask the question:

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can we bring this mechanism
on Earth directly?

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And the answer is no, by no means.

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The Sun is too big, the Sun is too hot,
the Sun is too dense,

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everything speaks against that;

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but... and the story about the but:

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we have to build machines,
clever machines;

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we, humans have to build machines

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in order to mimic this process,
in order to bring it on Earth.

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So, for that, we have to understand
a few little things of physics.

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Don't be afraid.

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You have to carefully distinguish
between fission and fusion.

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Fission is splitting heavy nuclei;
fusion is fusing light nuclei.

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And they both belong to the same process:

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it's a conversion of mass into energy,

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and that's Einstein's
famous formula E=mc²,

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and that's the common mechanism.

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And this energy is released just by speed,
by kinetic energy, by heat in other words.

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So it generates heat.

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And that's what we would like
to make use of.

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And for that, we have to use a trick.

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Instead of using conventional hydrogen,
we use versions of hydrogen.

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And these two so-called isotopes
are called deuterium and tritium.

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Deuterium is just heavy hydrogen,
tritium is super heavy hydrogen.

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They both are actually hydrogen isotopes,

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they behave like hydrogen,
just the mass is different.

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And you can much more easily fuse them
than conventional hydrogen,

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than the hydrogen we know
from the everyday world.

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And when we fuse them, they collide,

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and in the collision, they generate
a helium nucleus, an alpha particle,

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and a neutron, and lots of energy.

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And that's the process we would like
to make use of; we, fusion scientists.

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And in order to get a feeling
what is this fuel about:

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fusing one gram of deuterium-tritium

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releases the same energy
as burning 10 million grams of coal.

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And so, that's a fantastic fuel.

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And so, you can say: is it available
on Earth, or is it just a dream?

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And the answer is yes,
it is basically available.

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So, deuterium is found just in seawater,
in a low concentration,

49
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but we do not need much.

50
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Tritium is available on Earth

51
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by making use of a mechanism

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that generates tritium from lithium.

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And so, if you now
put everything together,

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you can say that a half-filled
bath tub of water and an accumulator -

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here, there's a lithium-ion
accumulator in this mobile phone -

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would release enough energy

57
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to supply an average European
for 25 years with electric energy.

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That's of course, a big, big promise.

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How to make it happen?

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And this big promise has driven
mankind for 50 years already

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to explore how it can work.

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And this diagram here shows
the early days of fusion research.

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It's from the 1950s,
so that's from Los Alamos [Lab]

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and they built a device, a machine.

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And there is this ring in the background -

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at the center of the photo,
there's a ring with a purple glow -

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and this ring, together with
what's surrounded by

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was called the Perhapsatron -

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and that's because the scientists
didn't know if it would work at all.

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It worked somehow, but not sufficiently,

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because the very basic problem of fusion
is fusion is very easy to do.

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The fundamental nuclear process
is known, and it's easy to do.

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The exercise is to make a lot
of fusion processes at the same time.

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Again, so we need a lot of fusion

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in order to generate
substantial amounts of energy.

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And so, it became obvious

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that one has to work on different things
in order to build the right machine.

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The Perhapsatron not being
the right machine was discarded.

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Many, many others followed,
other generations followed,

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and I would like to give you
an update on the current status.

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So, the magnetic field is very important:

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you have to make use of the magnetic field

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in order to confine this super hot gas
which we call plasma.

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And you might have seen a plasma
already in reality

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if you have seen the Northern Lights
or an Aurora Borealis.

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That's a photo through
the window of an airplane

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of the Aurora Borealis
over the Northern Pole.

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The structure of the Aurora Borealis -

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this stripe-like structure is given
by the magnetic field of the Earth.

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So this is naturally occurring.

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And the plasma is actually the ingredient
that's the boiling soup

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that makes fusion happen
so many times as it should be

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in order to really gain energy.

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That's in the kind of standard machine.

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We are building a fusion science:

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it is called tokamak -
tokamak not tomahawk;

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that's a big difference!

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The tokamak consists
of superconducting coils

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in which a very strong current is running.

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It is also based on a strong current
running in the actual plasma,

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and the plasma is ring-shaped.

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So this purple ring there,

103
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or this magenta ring shown there,

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is the actual plasma
that is attached to the magnetic field.

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That's the basic principle of a tokamak,

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and nowadays,

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we are brave enough
in fusion research to build big machines,

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because they must be big in order to have
a lot of fusion reactions.

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The biggest tokamak in the world,
now under construction,

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is the tokamak ITER
in the South of France.

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And it's a world tokamak in a sense.

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It's not only a big tokamak,
the biggest tokamak in the world,

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but it's also a world project,

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because in the ITER project,
half of mankind is involved:

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China, the USA, Russia, the EU,
India, Japan, and South Korea.

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They're all joining forces
in order to build

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this really big superconducting
tokamak in the South of France.

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And this machine is going
to start operating in 2025.

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This is a big, big project.

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There's another concept
which is called a stellarator.

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Stellarator means bringing
the [power of] a star on Earth.

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And here, in blue again,
the magnets are shown

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that generate a magnetic field.

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And in yellow,

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that's the shape of the plasma
given by the magnetic field geometry.

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Stellarators need optimization.

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What does optimization mean?

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Optimization means
setting up a number of criteria:

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good plasma stability,
improved heat insulation,

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equilibrium, confinement,
things like that.

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And you cast everything,
all these requirements,

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in a set of computer codes -

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very massive computer codes
with a lot of plasma theory in it -

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and then you have to do

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all these horribly complicated
calculations using supercomputers.

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And the supercomputer

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that has calculated the Wendelstein 7-X -
that's our stellarator -

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was the Cray X-MP.

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This device has more computer power
than the Cray X-MP -

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this goes back to the mid 80s,
and supercomputers look different now -

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but nevertheless,

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the computing power was sufficient
to determine the shape of the coils.

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These calculations were repeated
and confirmed many times,

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and so we are pretty confident

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that we have found
the right magnetic field.

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The Wendelstein 7-X stellarator
consists now of the following elements:

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the plasma - so that's
the shape of the plasma,

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it looks a little bit like
a twisted tire of a bicycle -

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the magnetic field coils,
these calculated magnetic field coils;

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another set of coils
to change the magnetic field a little bit;

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a massive steel structure
that carries these coils -

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each coil weighs six tonnes
and has a diameter of three meters -

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and of course,
also many pipes and connectors

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to connect the magnet system together;

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and also an outer vessel -

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it's a massive steel vessel

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because the coils
have to be operated in vacuum

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since, for superconductivity,

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you have to cool down the coils
to minus 270 degrees centigrade.

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That's then the outer shape
of the machine.

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It looks a little bit like a spaceship,

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So the "Science" magazine wrote

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it looks like
Han Solo’s Millennium Falcon,

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and they also wrote
this machine was designed in hell.

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It's all not true;

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it's just a kind of engineering exercise,
and that's the machine in reality.

167
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And you also have
the comparison to a person.

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It is a complicated machine.

169
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Four hundred technicians,
engineers, and scientists

170
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have worked 20 years to build the machine
in Greifswald, Northern Germany.

171
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Twenty years, one million assembly hours.

172
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And the machine is running.

173
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We were pushing the button,

174
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and the physicists in the center
did the job for us.

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In the inset, you also see the plasma.

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The plasma is glowing nicely
bluish and reddish.

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These are different stages
of the plasma development.

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The machine runs perfectly fine.

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That's very satisfying
after 20 years of construction,

180
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and we are putting a lot of hope
on the performance of this machine.

181
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And here's the performance:

182
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0.01 grams of hydrogen
were injected into the vessel,

183
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heated up with 4 million watts
of microwave power

184
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to 100 million degrees centigrade
for the electrons

185
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and 20 million degrees centigrade
for the hydrogen.

186
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That wasn't that bad
for the first step of the machine.

187
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We have to increase
the particle density by a factor of 5,

188
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which sounds easy,

189
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but it needs more heating power.

190
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We are currently upgrading the machine
to increase the heating power

191
00:10:05,050 --> 00:10:08,305
to ten million watts, to ten megawatts,
for ten-second pulses,

192
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and later on, also for longer ones.

193
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I would like to conclude.

194
00:10:12,290 --> 00:10:14,892
I would like to make
a case here for fusion.

195
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Fusion is clean;

196
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it has no CO₂ emission -
keyword 'climate change';

197
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no long term waste -
different from fission;

198
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it is abundant - enough fusion fuel
for millions of years;

199
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and it's accessible to everybody -

200
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so nobody owns the fusion fuel,
which is very important, of course;

201
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it's safe - there are
no catastrophic failures possible;

202
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and it's economic -

203
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the machines are expensive,
but the fuel cost is essentially zero.

204
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Two key machines in the world are:

205
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Wendelstein 7-X -

206
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here the mission is to help create
a hydrogen plasma for 30 minutes,

207
00:10:48,155 --> 00:10:51,828
and this has never been done before,
the standard is a few seconds up to now;

208
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and the ITER mission
is to create a fusion plasma

209
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which generates ten times more energy
than needed to create plasma.

210
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I think that will be a major breakthrough,

211
00:11:00,468 --> 00:11:03,555
and then, we have
a new primary energy source,

212
00:11:03,558 --> 00:11:04,884
and I should say

213
00:11:04,892 --> 00:11:10,290
this is the only new primary energy source
mankind is working on.

214
00:11:10,291 --> 00:11:11,684
Thank you for your attention.

215
00:11:11,685 --> 00:11:12,993
(Applause)