EFDA conducts training programmes designed to foster the next generation of fusion researchers. every year, up to ten post doctoral researchers are supported by efDa fellowships which can last for up to two years. recently, an efDa fellow installed a two-dimensional electron cyclotron emission diagnostic on asDeX upgrade.

“This is a totally new way of looking at many plasma instabilities. It gives us a lot of puzzling but interesting information” says Ivo Classen on the subject of his findings with the new diagnostic.

Fusion plasmas are prone to developing instabilities and many of them can seriously harm the plasma or even the reactor wall. It is therefore vital to learn as much as possible about the nature of these structures. An electron cyclotron emission (ECE) diagnostic is a good tool for studying plasma instabilities. A diagnostic of this type measures the radiation that the plasma electrons emit as they gyrate around magnetic field lines. From the data it is possible to derive the plasma temperature with good spatial resolution throughout the entire depth of the plasma. Instabilities appear as fluctuations of the measured temperature.

The EFDA Fellowship worked out really well for me. Throughout the two years, the EFDA support was very uncomplicated.


Ordinary ECE diagnostic systems measure along one line through the plasma. Their data does not show the full shape of the observed instability. The two-dimensional diagnostic used on ASDEX Upgrade now covers an area of 10 by 40
centimetres with very high resolution. “Many structures, like plasma edge instabilities or Alfvén modes only reveal their full structure if measured in two dimensions. Moreover, we can now determine their position very accurately” explains Ivo Classen who is affiliated with the Dutch fusion research institute FOM which also built the diagnostic. Classen did his Ph.D with the system which was originally installed on the TEXTOR tokamak in Jülich. Between 2008 and 2010, he was financed by an EFDA Fellowship to install the system at ASDEX Upgrade. His work brought about considerable interest and resulted in invited papers to the High Temperature Plasma Diagnostics conference 2010 and the EPS conference 2011. Ivo Classen continues to work at IPP on the ECE diagnostic and is currently investigating Alfvén modes.

Two-dimensional ECE is quite unique: the technique is a joint development of the University of California, Davis, USA; Postech, Korea and FOM, The Netherlands. Today three of the world’s major tokamaks are equipped with it: DIII-D in San Diego, USA, KSTAR in South Korea and ASDEX Upgrade in Garching, Germany.

reference: Classen et al. “2D electron cyclotron emission imaging at ASDEX Upgrade”, rev. sci. instrum. 81, 10d929 (2010)