NF.5 Temperature Milestones

The previous week I promised in the comment to @lighteye that I will show him that EAST accomplishment of 100 million degrees is not the unique one. Unfortunately, I could not find the nice table I remember from my studies - it has all the relevant machines and references of the measurements. So I will report similar performances in this article using a graph without references.

In the last month, you could notice the viral news how Chinese EAST tokamak achieved over 100 million Celsius degrees. Even though I am glad that fusion-related news got such media attention, I have to comment on how such sensationalism is a pure journalist thing.

New Temperature Unit

Before jumping to the graph, I would like to introduce an energy/temperature unit that plasma physicist use: ”electronvolt”, or short eV.

1 electronvolt corresponds to approximately 11 600 K or 11 300 ^oC.

Why would people use such random number will leave for another time. For now, you can see it as a more convenient way to write 10 000 ^oC only as 1 eV. Henceforth, 100 million ^oC will be about 10 000 eV or written even shorter: 10 keV (kiloelectronvolts).

Big Tokamaks

OK, if you stayed with me after introduction of electronvolt, I can show you the next graph:

Source: Figure 10.7 from McCracken & Stott, "Fusion - The Energy of Universe"

Let's ignore (for now) what is on the vertical axis and focus on the horizontal one that is showing ion temperature. What do you see? It goes up to 1 billion ^oC!!!

Two deuterium-tritium (D-T) tokamaks achieved over 100 million ^oC several times. The two tokamaks are Jount Europen Torus – JET (Culham, UK) and Toroidal Fusion Test Reactor (Princeton, USA), and they were the only ones who ever had deuterium-tritium experiments. On pages 199-200 of the popular booklet “Focus on JET” there are even listings how JET had reached 30 keV in 1996 and 40 keV in 1998.

The third big tokamak is Japanese Torus 60 Upgrade – JT-60U (Toki, Japan) that holds the record for “the best fusion plasma”. They also got over 40 keV using special heating technology that will be used on ITER. However, not that this was only "transient" plasma, i.e. such high temperature was temporal and not controllable.

Small & Medium Tokamaks

I look at the medium tokamaks that could make such temperatures, and this is what I found:

An article on DIII-D (San Diego, USA) clearly shows on Figure 8d that ion temperature goes over 10 keV.

I did not manage to find it, but possible Tore Supra (Cadarache, France), Alcator C-Mod (MIT, USA), ASDEX Upgrade (Garching, Germany) and K-STAR (Daejeon, South Korea) also had such results.

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Disclaimer: The reported numbers may not be records for the particular machine, they are here to illustrate that such machines are capable of getting the same or even larger temperature than EAST tokamak. The difficulty lies in the fact that scientists are not writing articles about those numbers, but rather explain interesting physics behind the plasma behavior. In other words - records and similar achievements are boring for us :D

Also note that I do not want to downgrade the achievement of EAST, as it is a HUGE milestone for that particular machine. Especially taking its relatively small size into consideration. However, such temperatures were routinely obtained on the other machines for the last 30 years. The main success of EAST lies in having such temperature for longer times than anybody before.

Please feel free to ask anything in the comments. I will either try to answer you in the comment or even make the new post.