What is Tokamak: Definition and 39 Discussions

A tokamak (; Russian: Токамáк) is a device which uses a powerful magnetic field to confine plasma in the shape of a torus. The tokamak is one of several types of magnetic confinement devices being developed to produce controlled thermonuclear fusion power. As of 2021, it is the leading candidate for a practical fusion reactor.Tokamaks were initially conceptualized in the 1950s by Soviet physicists Igor Tamm and Andrei Sakharov, inspired by a letter by Oleg Lavrentiev. The first working tokamak was attributed to the work of Natan Yavlinsky on the T-1 in 1958. It had been demonstrated that a stable plasma equilibrium requires magnetic field lines that wind around the torus in a helix. Devices like the z-pinch and stellarator had attempted this, but demonstrated serious instabilities. It was the development of the concept now known as the safety factor (labelled q in mathematical notation) that guided tokamak development; by arranging the reactor so this critical factor q was always greater than 1, the tokamaks strongly suppressed the instabilities which plagued earlier designs.
By the mid-1960s, the tokamak designs began to show greatly improved performance. The initial results were released in 1965, but were ignored; Lyman Spitzer dismissed them out of hand after noting potential problems in their system for measuring temperatures. A second set of results was published in 1968, this time claiming performance far in advance of any other machine. When these were also met skeptically, the Soviets invited a delegation from the United Kingdom to make their own measurements. These confirmed the Soviet results, and their 1969 publication resulted in a stampede of tokamak construction.
By the mid-1970s, dozens of tokamaks were in use around the world. By the late 1970s, these machines had reached all of the conditions needed for practical fusion, although not at the same time nor in a single reactor. With the goal of breakeven (a fusion energy gain factor equal to 1) now in sight, a new series of machines were designed that would run on a fusion fuel of deuterium and tritium. These machines, notably the Joint European Torus (JET), Tokamak Fusion Test Reactor (TFTR), had the explicit goal of reaching breakeven.
Instead, these machines demonstrated new problems that limited their performance. Solving these would require a much larger and more expensive machine, beyond the abilities of any one country. After an initial agreement between Ronald Reagan and Mikhail Gorbachev in November 1985, the International Thermonuclear Experimental Reactor (ITER) effort emerged and remains the primary international effort to develop practical fusion power. Many smaller designs, and offshoots like the spherical tokamak, continue to be used to investigate performance parameters and other issues. As of 2020, JET remains the record holder for fusion output, reaching 16 MW of output for 24 MW of input heating power.

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  1. Shreya

    Understanding the Plasma Confinement in Tokamak Reactor

    Please be kind to help. How is an electric field formed due to toroidal magnetic field? How does the introduction of a poloidal magnetic field confine the plasma? Please answer in the context of Nuclear Fusion Reactor (tokamak).
  2. A

    U-Shaped Coil Tokamak: Poloidal Field Control

    It is long known that the toroidal field alone is not sufficient to achieve toroidal force balance within a tokamak due to the field being bent and geometry restricting the field to be of even strength both within the inner and outer circumference of the ring. Induced current is thus used for...
  3. F

    Tokamak question: What happens when you shine a laser on the plasma?

    I really enjoy learning strange facts and while i would never assume to be a "Smart" person i do have the power to ask. So with a plasma fusion reactor like the tokamak or any other they have a viewing window to see the plasma bound in the toroidal magnetic field so what would happen if you...
  4. A

    Pulsed Tokamak Fusion: Net Energy Gain Possibility?

    Zpinch works by running a strong current through the plasma which sets up a field that tends to confine the plasma, so if the current is switched on rapidly the resulting temperature increase and B field increase tends to compress the plasma channel rapidly, at least this is how I understand the...
  5. A

    What materials are used for the tokamak toroid wall?

    There are two questions that arose in my mind, first of all tokamaks use toroidal field coils which create a toroidal field within the torus to shape the plasma and confine it, but here is a question, the toroid coils have a static B field produced from a DC current in them, what kind of metal...
  6. JF001

    I How is the viscosity of a plasma produced?

    Summary: I'm interested in knowing more about instabilities within plasma. Is the viscosity of plasma produced by thermal, magnetic, or gravitational effects (or even something else)? I had the opportunity to talk with multiple Ph.D. students during the summer and was especially interested in...
  7. jedishrfu

    B New Tokamak D Mode Success - Fusion is Almost Here

    https://arstechnica.com/science/2019/03/physicists-flip-the-d-in-tokamak-get-unexpectedly-good-result/ I wonder if it'll fit into a Tesla and then we can remake the Back to the Future with a Tesla movie.
  8. N

    China's Experimental Advanced Superconducting Tokamak (EAST)

    A team of scientists from China's Institute of Plasma Physics announced this week that plasma in its Experimental Advanced Superconducting Tokamak (EAST) would be ready to begin attempting to generate more energy than it uses, in a world first. I am dubious about more news that comes out of...
  9. A

    Tokamak plasma heating current

    I will make some assertions and then phrase a question , please correct me if necessary. So the tokamak works like a transformer where the primary is a coil winding while the secondary is a torus which contains plasma which being electrically conductive forms the secondary winding? The toroidal...
  10. T

    New approach to stabilize fusion plasmas

    https://phys.org/news/2019-01-scientists-stabilizes-fusion-plasmas.html By applying more RF power to the unstable 'bubbles' that form in the plasmas.
  11. G

    Why a D-D reaction in the Divertor Tokamak Test Facility?

    The DTT project proposal talks about a D-D reaction inside the future tokamak that is going to be built in Italy, Frascati. Which is the reason of this choise? The cross section is smaller than the D-T reaction one, and neutrons are less energetic. How this influences heat and particle exhaust...
  12. Jan Berkhout

    How is current induced in the plasma in a tokamak?

    For a Year 12 Assignment I have to do a seminar on how magnetic fields are involved with a certain topic. I chose nuclear fusion energy production and specifically the tokamak. I understand that a toroidal magnetic field is created when a current is sent through a solenoid wrapped in a torus...
  13. chandrahas

    Difference between a tokamak and a spherical tokamak

    The title question is quite self-explanatory. Despite the fact that Spherical tokamaks are more spherical in shape, what else differentiates the ST from the conventional tokamak. I've heard that ST's use reverse field configurations from a website but I am skeptical about this since the rest...
  14. rebc

    Tokamaks and plasma confinement

    I have the fundamental understanding of how tokamaks work. Now, why is it not ideal to confine plasmas using a z- or theta- pinch configurations?
  15. J

    When will JET switch to DT fuel and what is the latest news on the ST40 tokamak?

    http://www.pppl.gov/news/2016/09/pppl-director-stewart-prager-steps-down It appears that Stuart Prager is “stepping down” as director of PPPL. I wish him well. But in the announcement it refers to a “recent technical setback in the NSTX-U facility”. I had not heard previously of this set...
  16. S

    I Advice on accelerating deuterons in a tokamak like chamber

    I was wondering if it is possible to setup a Tokamak like chamber with some sort of varying magnetic field arrangement around it, that can accelerate deuterons or other light nuclei, as if those nuclei were 'pulled' by a constant electric field of between 1kV and 100 kV (n.b. this should not...
  17. G

    What drives the toroidal flow and current in a tokamak plasma?

    In a tokamak design what accelerates the plasma? Is it the current from the primary coils driving the plasma round?
  18. S

    Flux surface average for a tokamak

    I am trying to figure out the flux surface average of a 3D perturbation in a tokamak. For example what is the flux surface average of cos(m*theta+n*phi) at a given flux surface. (Theta and phi being poloidal and toroidal angles respectively?
  19. K

    How do stellarator vs tokamak generate electicity?

    if you can get nuclear fusion in a stellarator vs tokamak how does that heat energy use to drive energy? also is it d-t from lithium for stellarator vs tokamak or something else?
  20. U

    Can Ion Trapping Approaches Effectively Contain Fusion Plasma?

    I've been reading some about the ITER project, tokamaks, and other approaches to plasma containment. Why can't ion trapping approaches such as an orbitrap be used for fusion plasma containment?
  21. Teen4Ideas

    Is My Idea Valid? Nuclear Fusion Power

    So as we all know (or at least I assume) Global Warming is real and happening, I am a teen, 17, and not trying to get answers for homework or anything like that. I just want to know, is it possible to create fusion using the temperature found at active Geo-thermal sites to reach the temp...
  22. T

    Understanding Tokamak Heating: Exploring Maxwell's Equations and Magnetic Fields

    HI, Some things I want to confirm, somethings I need to be reminded of: So what I remember is that Magnetostatics - stationary charges Electrostatics - constant or slow moving charges And that an accelerating charge makes a magnetic field, but you need a time varying field to move charges. So...
  23. Warpspeed13

    Would it be possible to build a model tokamak

    Would it be possible to just get a swirling plasma in an acrylic tube kind of like the arc reactor in iron man? I'm not talking about anything close to the temperatures or pressures required for fusion just kind of a demo piece to show the general idea.
  24. rogerk8

    How Can I Design a Tokamak to Ignite Ordinary Air and Control Plasma Diameter?

    Hi! I wish to know how to design a Tokamak of my own. This Tokamak will of course be very tiny but my intention is to ignite ordinary air and control the plasma's poloidal diameter by poloidal coils placed along the torous. I wish to do two things with my Tokamak: 1) Ignite ordinary air of...
  25. N

    Field Lines in TOKAMAK: Pictures & How to Understand

    How look field lines in TOKAMAK? Do you have any picture? How I could physically make for a better understanding? (of paper, laser, ...)
  26. S

    Can Ferrofluids Be Used in Tokamak or Spheromak Fusion Devices?

    Hi, Is it possible to use a ferrofluid to create a tokamak/spheromak? If not, then why? http://en.wikipedia.org/wiki/Ferrofluid Ferrofluids can be composed of non-magnetic liquids containing magnetic particles in colloidal suspension.
  27. N

    Net movement of plasma in tokamak

    Hi, I've got conflicting impressions on the motion of particles in tokamak reactors. Wikipedia says that they generally follow the poloidal field lines due to the Lorentz force, whilst another site claimed that the promising results were due to the random motion of the particles within the...
  28. L

    Tokamak using elctrons instead of hydrogen nuclei

    Q.) What would happen if a *reverse-Tokamak* was created, thus reversing the electromagnets to a negative charge and repelling electrons into each other instead of fusing hydrogen nuclei, what approximate temperature would need to be used and would it work? If so what would occur?
  29. teroenza

    Tokamak Transformer Properties

    Hello all, I am a layman who is interested in nuclear fusion via magnetic confinement (the Tokamak setup). I recently read in a book about how the (a) transformer in the device could operate only for some number of "volt-seconds" before it had to be "recharged". This requires an additional...
  30. A

    Tokamak Miniaturization: Exploring the Potential for Portable Fusion Energy

    Assuming the ITER is a success, what would it take to be able to miniaturize it into something a little more portable?
  31. J

    Need help understanding how plasma in a Tokamak loses energy.

    Mainly I don't get how plasma loses energy by conduction, which is what I have read. Is it just from the collisions between plasma particles and the wall? Thanks!
  32. J

    How Does the Tokamak Facilitate Nuclear Fusion?

    Hi, I need to learn about nuclear fusion and how the Tokamak works. Can anyone recommend any books/texts/websites that would be useful? I am a 3rd year Physics undergrad and have done a reasonable amount of EM, to give you an idea of the level - I don't want a layman explanation but also not...
  33. Pattonias

    What happens to the Neutrons and Protons in a Tokamak reactor.

    As I understand it, the magnetic field confines the electrons because of the repulsion of the electrons in the plasma and the electrons traveling in the magnetic current. My question is what keeps the protons and neutrons released in the plasma from passing through the magnetic field in a...
  34. V

    Tokamak Fusion Requirements: Ideal Materials & Current

    What are the minimum standards for tokamak fusion? For instance, What are the ideal materials? Should you use deuterium, tritium, or a mixture of the two? How much current do you run through it before it confines the hydrogen gas enough to create fusion? Please answer.
  35. V

    Smallest Tokamak Reactor Size: Can it be in a Garage?

    What is the smallest size for a tokamak reactor? I was wondering if it was possible to create it in a garage or basement like a fusor.
  36. D

    Why do they use a huge tokamak?

    why do they use such a huge machine like the tokamak to try and sustain fusion? wouldn't it be easier to build a really small one? I'm guessing it would be a lot easier to recreate the conditions of the sun's core (extreme temp./pressure), assuming that's the blueprint for fusion, in a small...
  37. U

    Can Tokamak Reactors Achieve Break-Even Fusion?

    I have tryed to look into ITER and tokamak reactors latest updated information online, and cannot find any real specifics on it's latest progress. Does anyone know of where we are with producing sustained fusion for energy purposes, through currently using the tokamak? Is it possible to...
  38. C

    China’s Advanced TOKAMAK Experiment: Challenges & Solutions

    I recently read from newspapers that china has built a experimental advanced superconductive TOKAMAK , and such an experiment is going to set about. It also mentioned if the experiment exceeded, China would be the first country on the planet owing such a experimental equipment.I just roughly...
  39. P

    Practical material to use in tokamak

    could the use of buckminsterfullerene or bucky balls be a more practical material to use in tokamak because of the less friction it would create on the plasma?