Subscribe options

Select your newsletters:

Please enter your email address:

@

Your email address will only be used for the purpose of sending you the ITER Organization publication(s) that you have requested. ITER Organization will not transfer your email address or other personal data to any other party or use it for commercial purposes.

If you change your mind, you can easily unsubscribe by clicking the unsubscribe option at the bottom of an email you've received from ITER Organization.

For more information, see our Privacy policy.

News & Media

Latest ITER Newsline

  • Neutral Beam Test Facility | After upgrades, SPIDER testbed set to restart

    After a two-year shutdown for upgrades, the SPIDER testbed at the ITER Neutral Beam Test Facility in Padua, Italy, is preparing for commissioning and operation. [...]

    Read more

  • ITER Research Plan | Jointly preparing a new blueprint

    As part of work underway to update the ITER Project Baseline, a group of experts nominated by the Members met in February to evaluate the new blueprint for achi [...]

    Read more

  • On site | Component transfer goes electric

    On Friday 16 February, a toroidal field coil was moved from the Assembly Hall to a storage place a few hundred metres away. Quite a routine operation at ITER, a [...]

    Read more

  • Image of the Week | Director-General Barabaschi visits India

    Following his visit to China, Japan and Korea last autumn, ITER Director-General Pietro Barabaschi continued his tour of ITER stakeholders w [...]

    Read more

  • Science | Increasing fusion performance with energetic-particle-driven instabilities

    New results published in Physical Review Letters suggest that instabilities driven by energetic particles can have a positive impact on fusion performance. In t [...]

    Read more

Of Interest

See archived entries

An eye on the plasma edge

In terms of temperature and physical phenomena, the outer region of the plasma is ''very similar to the Sun's corona,'' says Robin Barnsley. © Soho-Nasa/Esa (Click to view larger version...)
In terms of temperature and physical phenomena, the outer region of the plasma is ''very similar to the Sun's corona,'' says Robin Barnsley. © Soho-Nasa/Esa
Impurities, in the form of particles detached from the machine components, will always find their way into a burning plasma. "They are unavoidable," explains Robin Barnsley, ITER Diagnostic Division Responsible Officer for spectroscopy. "It is important however, to detect and monitor them. Beyond certain limits, impurities would dilute the fusion fuel and degrade the reaction."

Impurities have different origins. Some are "expected," like the beryllium, tungsten, iron or carbon particles that come from the plasma-facing components of the machine. Others, like oxygen, copper or other metal particles, can originate from leaks or damage affecting other in-vessel components.

Because of the extremely high temperatures of the plasma, confined particles radiate light at specific wavelengths. They all have a "signature" that is both specific to their nature—beryllium will send a signal that is different from tungsten or copper—and to the temperature they are submitted to.

Identifying these signatures, and hence the nature and temperature of the particles, is the role of spectroscopy.

In ITER, several spectrometers will monitor different regions of the plasma in order to measure radiation and identify all relevant impurities. "Because of the very high temperature gradient in the plasma," explains Robin Barnsley, "light is emitted over the whole spectrum, from infrared,visible to ultra-violet and x-ray. No single spectrometer could survey the whole plasma in all those different wavelengths."

The vacuum ultra-violet (VUV) edge imaging spectrometer whose Procurement Arrangement was recently signed by ITER Director-General and the Head of the Korean Domestic Agency, is one of subsystems that, together, will monitor the ITER core, edge and divertor regions of the plasma. It is the first Procurement Arrangement to be signed for spectrometry diagnostic equipment.

The VUV edge imaging spectrometer will be looking at a region located at the upper edge of the D-shaped plasma which is typical of the outer 10% of its total volume. (Click to view larger version...)
The VUV edge imaging spectrometer will be looking at a region located at the upper edge of the D-shaped plasma which is typical of the outer 10% of its total volume.
The VUV edge imaging spectrometer , whose prototype is already under development and will be ready in two years, will be looking at a region located at the upper edge of the D-shaped plasma which is typical of the outer 10 percent of its total volume.

This is not the hottest part of the plasma: in terms of temperature (around one million degrees Celsius) and physical phenomena, this region is "very similar to the Sun's corona," says Robin Barnsley, who did his PhD in an X-ray astronomy group. "The physics and hence the instrumentation used for observation are closely related."

Data gathered in real-time by the VUV edge imaging spectrometer, along with that of other spectrometry devices observing other regions of the plasma, will enable the machine operators to adjust the plasma's parameters for optimal performance.


return to the latest published articles