3D Monte-Carlo-Simulation der ergodisierten Randschicht von TEXTOR-DED
3D Monte-Carlo-Simulation der ergodisierten Randschicht von TEXTOR-DED
In controlled nuclear fusion research, the science of edge plasma physics is of key importance in many ways: ideally, the edge plasma should transport the helium ash outward (towards the pump) and prevent that the surface released impurities penetrate the core plasma, while the hydrogen ions and the...
Saved in:
Personal Name(s): | Reiter, Detlev |
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Harting, Derek | |
Contributing Institute: |
Plasmaphysik; IEF-4 |
Imprint: |
Jülich
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
2005
|
Physical Description: |
VI, 138 Seiten |
Document Type: |
Report |
Series Title: |
Berichte des Forschungszentrums Jülich
4173 |
Link: |
OpenAccess |
Publikationsportal JuSER |
In controlled nuclear fusion research, the science of edge plasma physics is of key importance in many ways: ideally, the edge plasma should transport the helium ash outward (towards the pump) and prevent that the surface released impurities penetrate the core plasma, while the hydrogen ions and the energy are confined in the core plasma. To provide active control over the edge plasma region, a novel Dynamic Ergodic Divertor (DED) [6] was installed at the tokamak TEXTOR of Forschungszentrum J¨ulich. According to its conceptual design, the DED should spread the power load to the divertor plates over a larger area, and hence reduce erosion and sputtering of the first wall materials. At the same time, the particle removal of the toroidal pump limiter ALT-II should be maintained, or it might even be improved due to forced flows. All these tasks are currently under experimental observation. Furthermore, there are indications from earlier experiments and theory that the DED might modify the radial transport in the ergodized magnetic field of the edge plasma layer in such a way that the edge plasma can even shield the core plasma from the remaining eroded impurities. In doing so, the option of actively cooling the edge plasma by a radiation layer, in which recombination processes of deliberately introduced impurities (mostly nobel gases) emit a lot of photons and with them energy, may become more efficient. To achieve an ergodisation of the magnetic field structure in the edge plasma, a set of perturbation coils has been installed at the high field side of the vacuum vessel. These perturbation coils are arranged in such a way, that they run parallel with the magnetic field lines of the resonant q = 3 surface. The electrical circuit of the DED-coils can be changed, so that the perturbation field is resonant with the 12/4-mode, the 6/2-mode or the 3/1-mode. For this purpose, the perturbation coils can be supplied with a four phase current with up to 15 kA. The perturbation current may be DC (constant perturbation field) or AC to achieve a rotation of the perturbation field. The frequency of the perturbation current may either be set to 50 Hz or tuned in the frequency band between 1 kHz and 10 kHz. To achieve understanding about the behavior of edge plasmas with an ergodized layer, it is mandatory to accompany the experiment with numerical simulations of the ergodic edge plasma. Only this allows to quantify known edge plasma physics effects with sufficient detail in order to identify possibly new synergistic effects. For conventional toroidal symmetric magnetic field configurations of the edge plasma, there exists quite a number of 2D numerical edge plasma codes. Prior to the installation of the DED, the edge plasma of TEXTOR was simulated with some of them (e.g., with the B2-EIRENE code). But in case of the activated DED perturbation field, the toroidal symmetry is broken. Moreover, any common symmetry between the plasma flow to the targets and the backflow of neutral gas from the targets is lost, independent of the co-ordinate system chosen. One is forced to carry out the much more computing time intensive fully 3D plasma edge simulations. The same problem occurs in simulating stellarator edge plasmas. [...] |