JET physicists are ready to test the fuel for the ITER tokamak

The British tokamak Joint European torus (JET) will soon start testing a fuel mix that will be used in the future ITER, the largest experimental fusion reactor in the world. Nuclear fusion is a process that takes place in the sun. Mastering them can provide mankind with a nearly inexhaustible source of clean energy.

JET is 10 times smaller than ITER. In December was there with experiments Tritium began. With this, humanity is leading for the first time since 1997 Fusion reactions with significant amounts of this element.

In June of this year tests will begin with equal amounts of tritium and deuterium are involved in the reaction. This is exactly how ITER will work so that we can get more energy out of the fusion than we put into it. Until now, humanity has not been able to generate any net energy gain from the fusion.

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Finally, after years of preparation, we have reached the point where we can start testing. We are ready, says Joelle Mailloux, who heads the science program at JET. The experiments at JET will help scientists predict how this will work out Plasma in ITER and adjust the operating parameters of the large tokamak accordingly. This is the closest simulation of the ITER conditions that we can do at the moment, explains Tim Luce, chief scientist at ITER experiment. The tests JET is preparing for are the culmination of 2 decades of research. ITER is expected to be operational in 2025. At this point in time there will be low energies in him reactions carried out with hydrogen. From 2035, however, it will only use tritium and deuterium in a ratio of 1: 1. Both ITER and JET use a very strong magnetic field to hold and compress the plasma. The temperatures in the JET can reach 100 million degrees Celsius. This is many times higher than in the core of the sun.

The last experiments that mankind carried out with tritium fusion were only carried out at JET. The aim was to set a record for the ratio of energy gained to energy used. JET set a record of Q = 0,67 which is still valid today. The aim of this year's experiment is to achieve a similar result and maintain the reaction for at least 5 seconds. In this way, the scientists want to obtain data on the behavior of the plasma for a longer period of time.

Working with Tritium presents the specialists with new challenges. The specialists at JET have spent the past 2 years adjusting their equipment and preparing them to work with this radioactive element. Tritium has a very short half-life, occurs naturally in traces and is produced as an intermediate product by nuclear power plants. The total world production of tritium is only 20 kilograms.

As soon as the Tritium experiments the inside of JET becomes radioactive and must not be entered for 18 months. We had to change our procedures. Everything has to work the first time. We won't be able to go in there and tweak anything, explains Ian Chapman. During the tests, JET will use less than 60 grams of tritium, which is recycled. Fuel that contains a fraction of a gram of tritium is added 3 to 14 times a day tokamak injected. Each of these injections is a separate experiment with slightly different parameters, and each one gives the scientists 3 to 10 seconds of useful data. In this way we want to verify our current knowledge and use it for further work, says Mailloux. In some experiments only tritium is used, in others it is used Tritium and deuterium used in equal proportions.

With both types of experiments, the researchers want to understand how a higher mass of tritium affects the behavior of the Plasmas affects. This element has two neutrons in its nucleus, while deuterium has one, and hydrogen - none. This research will help predict what will happen in the ITER in the future. This is because the mass of the isotopes affects the magnetic field or the temperature of the plasma. "We need to investigate what is happening there and why it is happening," explains Anna White, a plasma physicist at MIT.

Another important difference to the last tritium experiments in 1997 is that the interior of JET is now lined with the same shielding materials as the interior of ITER. Since these materials can give off energy to the plasma and cool it down, understanding how they affect fusion is critical. And don't forget another very important factor. People. The last experiments with tritium were carried out 24 years ago. The new generation of physicists has absolutely no experience with this element. Now they have the opportunity to learn from more experienced colleagues.