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Latest ITER Newsline

  • Cryoplant | Filled from floor to ceiling

    The ITER cryoplant used to be a vast echoey chamber with 5,400 m² of interior space divided into two areas; now, it is filled from floor to ceiling with industr [...]

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  • Cryostat | Adjusting, welding, testing ...

    The assembly of the ITER cryostat—the stainless steel "thermos" that insulates the ultra-cold superconducting magnets from the environment—is progress [...]

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  • Tokamak Building | Full steam ahead

    In this central arena of the construction site, construction teams are active three shifts a day—two full work shifts and a third, at night, dedicated to moving [...]

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  • Poloidal field coils | Turning tables and hot resin

    One of only two manufacturing facilities located on the ITER site, the Poloidal Field Coils Winding Facility was constructed by Europe to house the winding, imp [...]

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  • Assembly Hall | One giant standing

    Two identical handling tools in the Assembly Hall will play a critical role in preparing ITER's nine vacuum vessel sectors for their final journey: transport by [...]

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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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