American scientists have presented the spherical tokamak a new type

National Spherical Torus Experiment (NSTX-U) (Photo: PPPL Office)

Laboratory of plasma physics at Princeton University, is currently working on a new design of fusion reactor. Your reactor scientists call a "star in a jar". The structure of most banks is very important. From its shape and other parameters depends on the efficiency of the reactor.

Usually the Central element of the tokamak similar to a doughnut. New design reactor, the National Spherical Torus Experiment (NSTX-U) is more like an Apple. At the moment the most advanced spherical tokamaks in the world — NSTX-U in the U.S. and MAST in the UK. According to the developers spherical tokamak allows for the reaction of nuclear fusion at much lower energy costs than in the case of a conventional tokamak.

The fact that the size of the hole in the center of the tokamak, where a plasma and is retained in a spherical fusion reactors can be two times smaller than the hole in a conventional reactor. In a spherical plasma reactor high pressure is formed in the relatively weak magnetic field, which needs much less energy than is necessary in standard analog.

Tokamak (toroidal chamber with magnetic coils) is the unit for magnetic plasma confinement to achieve conditions necessary for the occurrence of controlled thermonuclear fusion. Plasma in tokamak is not the chamber walls, which are not able to withstand the necessary thermonuclear reaction temperature, and the specially created combined magnetic field — the external toroidal and poloidal field of the current flowing in the plasma cord. Compared to other plants using magnetic field for plasma confinement, the use of electric current is the main feature of the tokamak. The plasma current provides the heating of the plasma and balance the plasma column in a vacuum chamber. This tokamak, in particular, is different from the stellarator, which is one of the alternative patterns of retention, in which both toroidal and poloidal fields are generated by external magnetic coils.


Scientists published information about your project in a reputable scientific journal Nuclear Fusion. Yet, experts say, the creation of a full-size reactor which can be used for commercial purposes, too early. This is only a model of a real fusion reactor. But in this model can already be obtained by first energy.

In NSTX-U will be tested materials that are suitable as structural elements of a nuclear reactor. Perhaps in the new reactor design will be able to get a self-sustaining fusion reaction. In tokamak NSTX-U will produce tritium, which is also the fuel. Initially, the reactor will need to download a certain amount of initial fuel (deuterium (2H) and tritium (3H)). As scientists hope, the reactor can consumed every atom of tritium to synthesize one atom of the same isotope of hydrogen.

The special design of the tokamak will ensure the emergence of the magnetic field of a special configuration. This, in turn, will allow to avoid negative impacts of too high temperatures on the reactor. The various elements of the tokamak can be extracted independently from each other for maintenance or repair. Technical work will be performed by robots, remotely.

The superconducting ring will replace the copper in the tokamak a new type. Such a change will have both positive and negative effect. A positive element is the reduction of energy consumption. Negative — would require additional protection of superconducting rings to temperature and radiation. Because of this, some have to increase the size of the installation. Thanks to new high-temperature conductors the current density they can raise. This means that the cross section of the magnets for a spherical tokamak will be reduced. In the Central column can be placed blanket, which is responsible for "breeding" tritium. American experts say that now the coefficient playback of tritium will be brought to 1.04 and 1.1.

Conventional tokamak in the form of a doughnut (image: Wikimedia)

"NSTX-U and MAST-U will expand the current horizons in physics, will give new information about high temperature plasma and will bring commercial installations," says project Manager Stuart Preydzher (Stewart Prager). He also claims that the reactor MAST production of a hot plasma of high density will pass without problems and negative aspects for the installation itself. These two tokamak are prototypes of full-scale fusion reactor Fusion Nuclear Science Facility to be built in 15 years.

"The main reason for the search of new design tokamak — hope to conduct a nuclear fusion reaction with less expenditure of resources than in the case of a standard tokamak," says one of the participants of the project. It may well be that spherical tokamaks is the forerunner of a full-fledged installations that will give humanity an inexhaustible source of energy. Perhaps the time when the "star in a jar" will start to give mankind energy is near.



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