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News & Media

Latest ITER Newsline

  • Neighbours | In goes the antenna

    Just a short distance from the ITER site, the Institute for Magnetic Fusion Research (IRFM) is modifying the Tore Supra plasma facility which, once transformed, [...]

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  • Remote handling | Off-site test facility for design evaluation

    Through a technical collaboration established between the ITER Organization and the UK Atomic Energy Authority (UKAEA) in 2017, the UKAEA's centre for Remote Ap [...]

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  • Poloidal field coils | A tailor-made ring

    They work like tailors, carefully taking measurements and cutting immaculate fabric with large pairs of scissors. But they're not making a white three-piece sui [...]

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  • Fusion world | Record results at KSTAR

    Experiments in the Korean tokamakKSTAR in 2017 achieved record-length periods of ELM suppression by the application of three-dimensional magnetic fields with in [...]

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  • JT-60 SA| Cryostat ready for Europe-Japan tokamak

    The cryostat vessel body of the JT-60SA tokamakhas been successfully manufactured and pre-assembled at a factory in Spain, and will soon be transferred to the J [...]

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Of Interest

See archived articles

Colour me a plasma

Phil Dooley, EFDA

Each element has its own colour, corresponding to the gaps between its electrons' energy levels. The human classification of today's plasma colour as salmon, or peach, or burnt sienna is quite irrelevant. But a fun discussion to have, nonetheless. (Click to view larger version...)
Each element has its own colour, corresponding to the gaps between its electrons' energy levels. The human classification of today's plasma colour as salmon, or peach, or burnt sienna is quite irrelevant. But a fun discussion to have, nonetheless.
Something that surprises many people when they see their first plasma pulse on a screen in the control room, is that the plasma is invisible. There is a bit of glow around the edges, and the divertor—the bottom area of the vessel where the plasma touches the tiles—glows red hot. But the core of the plasma, at something like 100 million degrees, is completely transparent.

This is a desirable characteristic — it means that there is no energy being lost via radiation. It comes about because the atoms of the hydrogen fuel have been completely stripped of their electrons, or ionised. When attached to a nucleus at lower temperatures, these electrons absorb and emit light as they jump between the energy levels, but once they are detached that mechanism is disabled, so no light is absorbed or emitted.

To become this transparent, of course all the electrons must be detached. There is a pink glow around the edges because the plasma is cooler and so some electrons are attached, but generally for deuterium and tritium atoms, their single electron is easily removed. But for all other elements, with more electrons, it is harder to remove every last one and therefore to completely prevent energy leaking out through in the form of radiation.

Read the full article at EFDA.


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