Tour of tokamaks: Alcator C-Mod

I had the opportunity two weeks ago to visit the Plasma Science & Fusion Center (PSFC) at MIT (that was my first visit and I was quite impressed to be in this temple of science and technology, but this is another story)) and to have a look at their tokamak: Alcator C-Mod.

The Alcator name is derived from the italian words Alto Campo Torus (the program was initiated by Bruno Coppi, born in Italy, and current leader of the very hyped Ignitor project.), which mean High Field Torus. The machine is the third of its class (yes, the predecessors were called A (operated in 1975, B designed but never built,  C operated in 1982 but which is a completely different machine) and started its operations in 1993.

At first sight, I was surprised to see how compact the machine is: a major radius of 0.67m but the torus itself and the coils are hidden behind thick concrete walls. However it has a very high magnetic field (5T on average, up to 8T, world-record) and can produce plasma at high pressure (for a tokamak plasma). AUxiliary heating includes ICRH (6MW) and Lower Hybrid (1.6MW).

Among the latest results from the machine, the possibility to decrease the local deposition of exhaust power by injection of impurities (see details). Indeed, a hot and dense plasma makes it possible to produce high amounts of power (which is what we want in the end), but too much exhaust power can lead to local overheating of the walls: a balance has to be found between these two requirements. To decrease the local flux of power, the idea is to seed some impurities (like Neon or Nitrogen) at the plasma edge: these impurities will radiate at other locations than the core plasma leading to a better distribution of the exhaust power.

Other results presented in non-technical languages are presented on the website of PSFC.

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One Response to Tour of tokamaks: Alcator C-Mod

  1. […] there are indeed many things to see in this temple of […]

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