Enable Recite

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

  • Fusion events | Bringing power to the people

    In tandem with the annual Fête de la Science, a French exhibition on the sciences, the European research consortium EUROfusion is premiering a new travelling ex [...]

    Read more

  • Fusion world | Stellarators "an option" for future power plants

    In the history of magnetic fusion, the photo is iconic. A smiling, bespectacled middle-aged man stands next to a strange contraption sitting on a makeshift wood [...]

    Read more

  • Divertor cassettes | Europe awards final contract

    Fifty-four divertor cassettes form the backbone of a unique system designed to exhaust waste gas from the ITER machine and minimize impurities in the plasma. In [...]

    Read more

  • Image of the week | 2nd central solenoid module on its way

    A second module for the ITER central solenoid, the "most powerful magnet in the world," is on its way to ITER. Procured by US ITER and manufactured b [...]

    Read more

  • Disruption mitigation | Perfecting the pellet

    ITER's success will depend in part on subduing potential plasma instabilities. A team at Oak Ridge National Laboratory in the United States is tackling the chal [...]

    Read more

Of Interest

See archived entries

Bouncing dust

Tracks of different types of dust particles in the plasma beam of Pilot-PSI: small velocity (a) loss to large velocity loss (b) and even sticking. Once a dust particle sticks to the surface, it cools down and is no longer visible. Credit: Andrey Shalpegin et.al.*, Nuclear Fusion (Click to view larger version...)
Tracks of different types of dust particles in the plasma beam of Pilot-PSI: small velocity (a) loss to large velocity loss (b) and even sticking. Once a dust particle sticks to the surface, it cools down and is no longer visible. Credit: Andrey Shalpegin et.al.*, Nuclear Fusion
When the hot, dense plasma in a fusion reactor hits the reactor's exhaust wall, dust particles will inevitably erode from the wall and be swept away by the plasma, or ionised gas. But how do these dust particles travel and where do they end up?

An international team has used sensitive cameras to produce the first ever fully resolved movies of dust motion in experiments with DIFFER's linear plasma generator Pilot-PSI (Nieuwegein, The Netherlands). The new data will feed into improved models for dust motion in the fusion reactor ITER.

"Dust particles are a few millionth of a metre (micrometre) in size. A challenge with detecting their minute motions is that you want to have the camera really close to the plasma," says Pilot-PSI operator Kirill Bystrov. In a complete fusion reactor, there is seldom the space to do that—instrumentation ports are too far away from this plasma-surface interaction region. "In Pilot-PSI, we can get the camera within half a metre of where the plasma hits the target."

The experiments reached a record spatial sensitivity of 9 micrometres per pixel. Previous experiments reached 200 micrometres to a few millimetres per pixel - ten to fifty times less sensitive than the record set in Pilot-PSI. This gives unparallelled information about how the dust particles roll, skip and bounce, and how they are influenced by the constant wind of plasma particles. This information will feed into predictive models for the dust motion, to clear up where it will collect and which reactor areas need special focus when cleaning.

The new measurements managed to clear up a mysterious form of motion where a dust speck kept its high temperature while sliding across a cooled surface. Intuitively, that just cannot happen: the particle should cool down to the surface temperature if it is in constant contact. It turns out the 200 micrometre per pixel resolution of the original measurements was to blame - where they saw a particle rolling or sliding in constant contact with the cooled surface, the more accurate 9 micrometre video clearly shows the dust speck bouncing across the surface and only cooling down a fraction when it strikes the surface between bounces.

Source: Highly resolved measurements of dust motion in the sheath boundary of magnetized plasmas; A. Shalpegin, F. Brochard, S. Ratynskaia, P. Tolias, M. De Angeli, L. Vignitchouk, I. Bykov, S. Bardin, K. Bystrov, T. Morgan

Read the full report on the DIFFER website.


return to the latest published articles