Browsing by Author "Manso, M.E."
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- Changes in the density profile due to the m=2 tearing mode in asdexPublication . Manso, M.E.; Silva, A.; Serra, F.; Matias, José; Mendonça, J.; Zohm, H.; Kluber, O.; Soldner, F.X.Resistive MHO tearing modes can develop magnetic islands near the rational magnetic surfaces, where q=m/ n.
- Experimental determination of the transient transport and of fluctuations relevant to transport in ASDEXPublication . Niedermeyer, H.; Dodel, G.; Hendler, M.; Fussmann, G.; Gehre, O.; Gentile, K.W.; Giannone, L.; Holzhauer, E.; Krieger, K.; Rudyj, A.; Theimer, G.; Bengtson, R.D.; Carlson, A.; Eberhagen, A.; Engelhardt, W.; Gernhardt, J.; Gruber, O.; Hofmann, J.V.; Karger, F.; Kluber, O.; Kramer, M; Manso, M.E.; Matias, JoséParticle transport was studied in ASDEZ with modulated puffing of the discharge gas and of impurities. The energy transport is investigated by numerical simulation of the heat pulse after the swatooth crash. Small scale density fluctuations are investigated in the confinement region with far infrared scattering and reflectometry and in the edge plasma with langmuir probes and Ha diagnostic. In addition to a diffuse component of the particle transport, a strong inward drift is observed in all discharges. In ohmic discharges the transport coefficients decrease and saturate like 1/TE with increasing density. They are smaller in deuterium that in hydrogen. In the improved ohmic confinement (IOC)regime mainly D in the outer region is reduced. D increases proportionally to the heating power in L-mode discharges. The improvement of particle confinement in the H-mode is explained by a increase of the inward drift at the edge rather than a decrease of D. The impurity diffusion coefficient is independent of the impurity mass and charge. In ohmic discharges, it varies with ne like the bulk diffusion coefficient, is independent of B or increases weakly with B and increases with Ip. In L-mode discharges, Dimp increases linearly with the heating power. The electron thermal condustivity determined by heat pulse propagation exceeds the stationary value by a factor of 3-4, assuming merely diffusive heat transport. Convection does not significantly reduce this factor. however, non-diagonal terms.
- Localized density measurements on ASDEX using microwave reflectometryPublication . Manso, M.E.; Serra, F.; Silva, A.; Matias, José; Nunes, F.; Leitão, J.; Mata, J.; Varela, P.; Vergamota, S.; Neves, J.; Pereira, J.; Cupido, L.; Soldner, F.X.; Siller, G.Reflectometry is based on the propagation and reflection of probing waves in the inhomogeneous fusion plasma.
- Recent results of H-mode studies on asdexPublication . Wagner, F.; Field, A.R.; Fussmann, G.; Hofmann, J.V.; Manso, M.E.; Vollmer, O.; Matias, JoséIn a comparative study of various confinement regimes the H-mode demonstrated the best performance. Confinement enhancement factors (above ITER 89-P L-mode scaling) in the range of 1.6 fH 2.8 have been achieved with values depending on the divertor configuration, the wall condition, ELM behaviour and the plasma ion spicies. Long-pulse H-phases, withELMs, of up to 3.5s with constant confinement time, recycling and impurity characteristics are archived. H* -mode operation is possible without a loss of current scaling at qa values as low as 2.2. The B-limit is the same with and without ELMs. Murakami parameters are similar in H-and L-modes.
- Reflectometry measurements of the m=1 satellite mode in L- and H-mode plamas in ASDEXPublication . Serra, F.; Manso, M.E.; Silva, A.; Matias, José; Wagner, F.; Zohm, H.; Kallenbach, A.; Varela, P.In ASDEX, with strong NB, heating, often a large central m=1, n=1 mode is observed on the SXR emission. For PNBI > 1 MW a mode rotating with the same frequency, the so-called`m=1 satellite`, is seen on the magnetic pick-up coils in the L and H-phases. Magnetic measurement s in the divertor chamber suggest that the satellite mode might be located outside the separatix, on open field lines reaching the diretor /1/. Here we present results from localized microave reflectrometric measurements. The time evolution of the satellite mode frequency is studied for plasmas with different qa and the mode localization is estimated, confirming that is shoud be close to but outside the separatrix. The central toroidal rotation velocities of the plasma can be inferred from the measured frenquencies of the satellite modes.