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In this work, the in uence of a 3D boundary induced by resonant magnetic perturbations (RMPs) on the material migration, i. e. the erosion from wall material due to the plasma surface interaction and the transport of these impurities is investigated for the rst time. With applied RMPs two new domains occur in the magnetic eld structure. Three dimensional SOL ux tubes with predominantly transport parallel to short magnetic eld lines and a region of longer stochastic eld lines with diusive gradient driven radial transport. The plasma wall interaction and the material transport in these domains were investigated. A globally higher radial electric eld Er as well as local changes in the magnetic eld structure such as pressure driven sonic ows or locally higher Er elds can potentially in uence the material transport with applied RMPs. The experiments were performed at the tokamak TEXTOR, the RMPs were induced by the dynamic ergodic divertor (DED). The plasma discharges and DED application was chosen to have a spatially separated 3D structure to be able to investigate the underlying physics. Two spherical carbon test limiters were positioned in dierent poloidal and toroidal positions which allowed to analyse the material migration in a 3D SOL ux tube and a stochastic region at the same time. Methane doped with 13C was injected through the test limiters during three dierent plasma scenarios, without RMPs, with static RMPs and an RMP sweep. The test limiters and the injected methane were monitored in situ with dierent cameras and spectrometers. The deposition of the injected particles was measured post mortem by colourimetry, nuclear reaction analysis and secondary ion mass spectrometry. The most profound change from no RMP to the RMP cases is a 90 re-direction of the low ionised carbon C+ and C2+ into the ErB-drift direction. From a comparison of the experiments and numerical eld line tracing it was found that this is a global eect occurring in both 3D domains during applied RMPs. Modelling with the impurity tracing and plasma wall interaction code ERO supports a 2-3 times higher radial electric eld at the test limiter positions compared to the unperturbed boundary. Local changes from the plasma geometry do not play a role. Post mortem analysis reveals that the deposition pattern is less in uenced by the higher ErB-drift. ERO modelling shows that the pattern is formed by CH+4 and CH+3 . Due to the higher mass of the molecules a re-direction is strongly localised close to the injection location. Fist estimations on the material migration in divertor machines indicate a high potential of RMPs to change the net-deposition in future fusion devices such as ITER. Furthermore, the local deuterium retention increased by a factor of 2-2.4 during RMPs due to a decrease in the surface temperature. Independent from the RMP application, the local deposition eciency of the injected particles was more than a factor of 10 higher for test limiters with high surface temperatures Tsurf 2700C compared to lower temperatures. A reason for this can be an easier binding of the injected particles to the surface as it is less stable close to the sublimation temperature.
Buchkauf
Material migration in tokamak plasmas with a three-dimensional boundary, Ruth Laengner
- Sprache
- Erscheinungsdatum
- 2013
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- Titel
- Material migration in tokamak plasmas with a three-dimensional boundary
- Sprache
- Englisch
- Autor*innen
- Ruth Laengner
- Erscheinungsdatum
- 2013
- ISBN10
- 3893369244
- ISBN13
- 9783893369249
- Kategorie
- Skripten & Universitätslehrbücher
- Beschreibung
- In this work, the in uence of a 3D boundary induced by resonant magnetic perturbations (RMPs) on the material migration, i. e. the erosion from wall material due to the plasma surface interaction and the transport of these impurities is investigated for the rst time. With applied RMPs two new domains occur in the magnetic eld structure. Three dimensional SOL ux tubes with predominantly transport parallel to short magnetic eld lines and a region of longer stochastic eld lines with diusive gradient driven radial transport. The plasma wall interaction and the material transport in these domains were investigated. A globally higher radial electric eld Er as well as local changes in the magnetic eld structure such as pressure driven sonic ows or locally higher Er elds can potentially in uence the material transport with applied RMPs. The experiments were performed at the tokamak TEXTOR, the RMPs were induced by the dynamic ergodic divertor (DED). The plasma discharges and DED application was chosen to have a spatially separated 3D structure to be able to investigate the underlying physics. Two spherical carbon test limiters were positioned in dierent poloidal and toroidal positions which allowed to analyse the material migration in a 3D SOL ux tube and a stochastic region at the same time. Methane doped with 13C was injected through the test limiters during three dierent plasma scenarios, without RMPs, with static RMPs and an RMP sweep. The test limiters and the injected methane were monitored in situ with dierent cameras and spectrometers. The deposition of the injected particles was measured post mortem by colourimetry, nuclear reaction analysis and secondary ion mass spectrometry. The most profound change from no RMP to the RMP cases is a 90 re-direction of the low ionised carbon C+ and C2+ into the ErB-drift direction. From a comparison of the experiments and numerical eld line tracing it was found that this is a global eect occurring in both 3D domains during applied RMPs. Modelling with the impurity tracing and plasma wall interaction code ERO supports a 2-3 times higher radial electric eld at the test limiter positions compared to the unperturbed boundary. Local changes from the plasma geometry do not play a role. Post mortem analysis reveals that the deposition pattern is less in uenced by the higher ErB-drift. ERO modelling shows that the pattern is formed by CH+4 and CH+3 . Due to the higher mass of the molecules a re-direction is strongly localised close to the injection location. Fist estimations on the material migration in divertor machines indicate a high potential of RMPs to change the net-deposition in future fusion devices such as ITER. Furthermore, the local deuterium retention increased by a factor of 2-2.4 during RMPs due to a decrease in the surface temperature. Independent from the RMP application, the local deposition eciency of the injected particles was more than a factor of 10 higher for test limiters with high surface temperatures Tsurf 2700C compared to lower temperatures. A reason for this can be an easier binding of the injected particles to the surface as it is less stable close to the sublimation temperature.