Transport barriers in hot magnetized plasmas - in search for the missing link
05 / 2004 - 04 / 2007
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)
Fluctuations in the electric and magnetic fields in a hot plasma form turbulent eddies, that drive significant transport. By carefully selecting the plasma conditions, it is possible to quench the turbulence locally. Such regions of quenched turbulence are referred to as transport barriers. Important aspects of the transport barrier formation process are not yet understood. Especially the preference of transport barriers to form in the vicinity of certain magnetic flux surfaces is enigmatic. Theoretical calculations have matured in the sense that they now are able to predict the dynamic behaviour of the turbulent eddies to a high level of detail. However, to make the link between the theoretical predictions and the experiment, in-situ measurements of the turbulent eddies in the plasma core are required. This link is missing. We are now in the unique position to fill this gap by a well coordinated research programme on the T-10 (Moscow) and TEXTOR (Jülich, Germany) tokamaks. The latter device is the home-machine for FOM Rijnhuizen. The two machines have almost the same parameters (geometry, magnetic field, plasma current, etcetera) and, as has been already observed, also the physics underlying the formation of transport barriers in the two machines is quite similar. Each of the two devices has a range of tools to locally change the plasma conditions and, hence, to induce various types of transport barriers. Moreover, they are recently equipped with state-of-the-art plasma diagnostics that will allow us to perform, for the first time, detailed measurements of important fluctuation plasma quantities in a large number of sample volumes in the vicinity of the transport barrier. The most important diagnostics on the two machines are complementary and therefore the transport barrier research in the two machines, under similar plasma conditions, but using different diagnostics will give important additional insight. Last but not least, because of their circular cross section, the T-10 and TEXTOR plasmas are ideally suited as a target for theoretical calculations. Extensive theoretical calculations will be performed for the specific plasma conditions that are used in the experiment to test the various hypotheses for transport barrier formation that have been described in literature.