On the last day of work, the MTI tokamak set a new world record for plasma pressure

Scientists and engineers from the Massachusetts Institute of Technology have broken their own world record for plasma pressure, a key component for obtaining energy from fusion in tokamak. In the atomic reactor Alcator C-Mod , the result was achieved at 2.05 atmospheres, which is 15% higher than the previous one.

The experiment was carried out on the last day of operation of the Alcator C-Mod - September 23, 2016. Financing of the project is finished . The Alcator C-Mod reactor has been in operation at MIT for 23 years, and during this time it has repeatedly set a plasma pressure record in tokamak. The previous one at 1.77 atmospheres was installed in 2005.
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C-mod is the world's only compact fusion reactor that can create a magnetic field by induction of 8 Tesla - 160 thousand times stronger than the magnetic field of the Earth. It allows you to create a dense, hot plasma, which can be stable at temperatures above 80 million degrees Celsius.

To achieve a record effect, MIT researchers created a 5.7 Tesla magnetic field. This was enough to heat the plasma to 35 million degrees Celsius - a temperature twice the heat of the solar core. It took 4 megawatts of energy to heat the plasma. During the experiment, 300 trillion fusion reactions per second occurred in the plasma.

“This result confirms that the high pressure required for plasma combustion is best achieved with high magnetic field tokamaks, such as the C-Mod Alcator,” said Riccardo Betty, professor at the Faculty of Mechanical Engineering and Astronomy at the University of Rochester. In addition to MIT physicists, scientists from the Princeton Laboratory of Plasma Physics, the Oak Ridge National Laboratory, and General Atomics took part in organizing the experiment.

“This is a remarkable achievement that highlights the highly successful Alcator C-Mod program at the Massachusetts Institute of Technology. Record plasma pressure brings us closer to practical fusion energy, ” notes Dale Mead , a former deputy director of the Princeton Laboratory of Plasma Physics, who was not directly involved in the experiment.


In order for the fusion reaction to proceed successfully on Earth, you need to learn how to keep hot (above 50 million degrees) plasma in a tokamak in a stable state under high pressure in a certain volume. That is why so far the scientists of the Massachusetts Institute of Technology have been paying particular attention to this variable. Their tokamak is leading in terms of pressure, while the other two variables, volume and temperature, pay little attention. The staff of MTI are sure: if scientists all over the world manage to solve the problem of pressure, one can say that 2/3 of the way to obtaining a source of thermonuclear energy has already been passed.



Thermonuclear fusion is the same process that occurs in the depths of the Sun. In essence, the star is a natural thermonuclear reactor. The energy released during the synthesis is enough to emit powerful streams of light and particles. If on Earth it is possible to reproduce the conditions under which two light atomic nuclei can unite into a heavier one, overcoming repulsive forces, then in the long run, humanity can replace traditional nuclear power plants. This solution has many advantages. The main components of the fuel - deuterium and tritium - are extracted from water and lithium. Deuterium is enough for us for millions of years, lithium - for several hundred years. In addition, power plants will be safer. The density of the fuel in the reaction space will be very low: within 1 gram of deuterium / tritium fuel per 1000 cubic meters. Any failure will cool the plasma and stop the reactions, and deuterium, lithium and helium produced during the reaction are not radioactive. Only tritium is dangerous, but its half-life is only 12.6 years. It will be manufactured and used in a nuclear reactor, so the designs of nuclear power plants will be designed in such a way as to avoid its release. And finally, at the power stations of the future, energy will be generated without spent nuclear fuel. That is why scientists around the world are making so much effort to achieve the goal, despite the fact that this may take a dozen years.

Today, the main obstacle is the fact that reactors use more energy than they create. During the rotation of the hot plasma, short flashes occur which tokamaks cannot withstand for a long time. 6 minutes and 30 seconds is a record that the French tokamak was able to set in 2003. Ideally, it is necessary to create a reactor that can produce a self-sustaining plasma. Therefore, 35 countries, including Russia, the USA, China and the European Union, are now investing in the construction of the ITER reactor in France, which should solve this problem. The US government, which is also interested in construction, has decided to abandon the financing of Alcator C-Mod in favor of ITER. In the implementation of this project, in essence, the most important and significant achievements that have been achieved in the structures and materials for C-Mod are used.



Now, the MIT nuclear fusion group will try to use new high-temperature superconductors that can produce magnetic fields stronger without heating and energy consumption. These superconductors should be the basis of the design of the 270 Megawatt Affordable Robust Compact reactor. It is assumed that ARC will be able to produce the same amount of energy as ITER, but will be two times smaller in size.