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News & Media

Latest ITER Newsline

  • 23rd ITER Council | Pace and performance on track

    Working as an integrated team, the ITER Organization and seven Domestic Agencies are continuing to meet the project's demanding schedule to First Plasma in 2025 [...]

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  • Huffing and puffing | Testing the endurance of steering mirrors

    On the computer screen, a set of three metal bellows 'breathe' in a steady rhythm. Nuclear engineer Natalia Casal and materials engineer Toshimichi Omori are on [...]

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  • ITER R&D | News from the Neutral Beam Test Facility

    At Consorzio RFX, where ITER's most powerful external heating system will be tested in advance, activities are progressing well on two distinct test beds. ITE [...]

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  • Vacuum vessel welding | Rehearsing a grand production

    There is a place near Santander, Spain, where one can actually feel what ITER will be like. Although we've seen dozens of drawings and 3D animations, the encoun [...]

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  • Image of the week | A plasma-enlightened training course

    The Vacuum Section hosted approximately 40 people last week from the ITER Organization and the Domestic Agencies for a two-day training session on vacuum. [...]

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Of Interest

See archived entries

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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