Thirty Seconds At 100 Megakelvins

Back in Dec 2020 we wrote about the Korea Superconducting Tokamak Advanced Research (KSTAR) magnetic fusion reactor’s record-breaking feat of heating hydrogen plasma up to 100 megakelvins for 20 seconds. Last month it broke its own record, extending that to 30 seconds. The target of the program is 300 seconds by 2026. There is a bit of competition going, as KSTAR’s Chinese partner in the International Thermonuclear Experimental Reactor (ITER), the Experimental Advanced Superconducting Tokamak (EAST) did a run a week later reaching 70 million degrees for 1056 seconds. It should be noted that KSTAR is reaching these temperatures by heating ions in the plasma, while EAST takes a different approach acting on the electrons.

The news reports seem to be using Celsius and Kelvins interchangeably, but at millions of degrees, that’s probably much smaller than measurement error. These various milestones are but stepping stones along the path to create a demonstration large fusion reactor, the goal of the global ITER mega-project. Currently China, the EU including Switzerland and the UK, India, Japan, Russia, South Korea, and the United States are members of ITER, and Australia, Canada, Kazakhstan, and Thailand are participants. The ITER demonstration reactor is being constructed at the Cadarache facility located 60 km northeast of Marseille, France, and is on track for commissioning phase to begin in 2025, going operational ten years later.

28 thoughts on “Thirty Seconds At 100 Megakelvins

    1. 1) In the core, where it matters, about 15 MK or MdegC
      2) See answer 1, it really doesn’t matter

      But what does matter is the product of pressure (or density), temperature and time (average energy confinement time not pulse length).

      Not knocking the present experimental reactors. They’re great. But none have yet got the product large enough. They are all useful stepping stones on the way to learning how to achieve it. Hopefully ITER will.

      The exciting thing about long pulses in a Tokamak is more that the machine could (if the product were high enough), generate power for longer pulses, which is potentially more useful (or at least easier on the machine) than short pulses.

    1. as long as you keep using tokamaks. it just seems that when a scientists says “this experiment will take 30 years” the media says “fusion in 30 years” (if only the media had the same use-of-language standards as science does). 30 years also seems to be the amount of time to fund, build and test a tokamak facility. you can just multiply the estimated number of tokamaks that have to be build by the average time to build. since you need to go through iter-> demo -> first power plant actual, and that were about 10 years into iter, my estimate is 80 years.

      1. Tokamak research and ITER in particular is a boondoggle, because there’s no serious investment in fusion technology going on. It’s just a project to “keep the lights on” so to speak: with minimum funding available, concentrate it on a project which takes up the maximum amount of time, resources and researchers, so anyone else couldn’t come out of the left field and take the trophy.

        Of course they don’t know if it will ever work in a satisfactory way, but that’s alright as long as nobody else gets any money. They say the ITER is “necessary” as a test bed for developing materials and methods to be used by everyone else, but it’s 10 years behind the curve from the other contenders like the W7-X and waiting for ITER/DEMO is really holding everyone else back.

      2. There is lots of research of alternative solutions, but tokamaks have come the furthest in terms of engineering.

        Also there is an assumption that it is a binary solution i.e we get fusion or don’t, but the experiments and engineering has made progress in a number of areas that can be applied outside fusion research.

        If we do achieve commercial sustainable fusion that would be the cherry on the cake, however it is one of these occasions that even the process of attempting creates huge fringe benefits

        However the challenges are huge, but so are the rewards and actually the money spent is not that huge compared to say the military complex.

    1. These aren’t fusion test machines: KSTAR and EAST are intended to study plasma heating and control. They can’t produce (significant) fusion since they don’t use D-T fuel.

      So what do you do with the heat? Nothing: you’re just studying how you heat plasma.

      KSTAR studies ion heating, EAST studies electron heating. In a real reactor you’d use both, but obviously you build dedicated machines for each.

  1. ok i was thrown for a little contrasting ion heating and electron heating. but now i realize, even my naive understanding of plasma might suggest the difference. i guess a plasma has most of the electrons free, not associated with any particular nucleus. so the plasma is positive nucleuses (“ions”) floating around in a sea of negative electrons, and you could act on either. anyways, i looked it up and it’s the same mechanism: expose it to an oscillating EM field at the right frequency to transfer energy into the part you’re interested in. so i guess they just use a different frequency to transfer energy to the lighter electrons.

    so i guess there was no reason for my double take but there i threw some words at the wall.

    i also have the idea that the practical way forward is going to be a pipeline sort of system where the plasma is heated to higher temps in a series of stages as it moves along a path, until it fuses and then is allowed to shoot out energetically along one axis, rather than attempting to confine it while it’s at its hottest temperature. super naive thought on my part.

    1. “anyways, i looked it up and it’s the same mechanism: expose it to an oscillating EM field at the right frequency to transfer energy into the part you’re interested in.”

      Partly – central ion heating can also be done with neutral beam injection, where you inject high velocity neutral deuterium which rapidly transfers energy via collisional losses. KSTAR uses both NBI and ion cyclotron resonance heating (ICRH, which is what it’s called when you target the ions).

      You might think “oh, then EAST just must use electron cyclotron resonance heating (ECRH)” but no, it’s not exactly that they’re focusing on *heating* the electrons differently, but *containing* a high temperature electron plasma. It’s the magnetic field arrangement that’s different between EAST/KSTAR.

    1. yes they have…several countries literally burned most of their forests before discovering coal. Since then, the energy demand increased by several orders of magnitude.
      Burning plants for power is stupid. Photovoltaics get you almost 20% efficiency even in real conditions. Solar thermal even more. Photosynthesis struggles to reach 1%, and then you have more losses with the burning and heat engine.

    2. Has anyone thought of burning wood for fuel.

      That’s the simplest form of harnessing fusion, which scientists say should be no closer than 150 million kilometres in order to be safe. (Even then, lots of people will get cancer from it!)

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