| 1. |
- Anderson, Johan, 1973, et al.
(författare)
-
Electron Geodesic Acoustic Modes in Electron Temperature Gradient Mode Turbulence
- 2012
-
Ingår i: Proceedings 39th EPS/16th ICPP, Stockholm 2-6 July 2012. - 9781622769810 ; 2, s. 814-817
-
Konferensbidrag (refereegranskat)abstract
- There has been overwhelming evidence that coherent structures such as vortices, streamers and zonal flows (m = n = 0, where m and n are the poloidal and toroidal modenumbers respectively) play a critical role in determining the overall transport in magnetically confined plasmas. The Geodesic Acoustic Mode (GAM) is the oscillatory counterpart of the zonal flow (m = n = 0 in the potential perturbation, m = 1, n = 0 in the perturbations in density, temperature and parallel velocity) and thus a much weaker effect on turbulence is expected. Nevertheless experimental studies suggest that GAMs (n = 0, m = 1) are related to the L-H transition and transport barriers. The electron-temperature-gradient (ETG) mode driven by a combination of electron temperature gradients and field line curvature effects is a likely candidate for driving electron heat transport. The ETG mode driven electron heat transport is determined by short scale fluctuations that do not influence ion heat transport and is largely unaffected by the large scale flows stabilizing ion-temperature-gradient (ITG) modes. We have utilized a fluid model for the ETG mode based on the Braghinskii equations with non-adiabatic ions including impurities and finite β - effects. The ETG mode model consists of electron continuity, electron parallel momentum and energy equations in combination of an non-adiabatic ion response. The ion and electron counterparts are coupled using quasineutrality. We use the wave kinetic equation to describe the background short scale ETG turbulence and derive an dispersion relation for the GAM. In describing the large scale plasma flow dynamics it is assumed that there is a sufficient spectral gap between the small scale fluctuations and the large scale flow. We note that the linear GAM is purely oscillatory and non-linearly the electron GAM is unstable with a growth rate depending on the saturation level |φk|2. To estimate the ETG turbulent fluctuation level and GAM growth, a predator-prey model was used to describe the coupling between the GAMs and small scale ETG turbulence. The stationary point of the coupled system implies that the ETG saturation level φk can be drastically enhanced by a new saturation mechanism, stemming from a balance between the Landau damping and the GAM growth rate.
|
|
| 2. |
|
|
| 3. |
- Coenen, J. W., et al.
(författare)
-
Tungsten erosion in the all-metal tokamaks JET and ASDEX Upgrade
- 2012
-
Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics. - 9781622769810 ; , s. 253-256
-
Konferensbidrag (refereegranskat)abstract
- The tungsten source in the all W outer divertor and Be main wall configuration has been quantified mainly during L-mode plasmas and compared to AUG Data both gained from local spectroscopy. Results so far show differences between AUG and JET based on impurities in the plasma changing the sputter behavior. This stresses the need for detailed analysis of the divertor impurity composition and detailed molding in the future analysis. The H-Mode examples indicate at ELM dominated sputtering and a rather low averaged sputtering yield in general. Nitrogen seeding can change the divertor conditions significantly either increasing W sputtering or suppressing it due to local cooling, JET and AUG behave similarly. All together it is clear that by having low divertor temperature or a beneficial impurity composition sputtering can be controlled and is rather low as expected in an all metal environment.
|
|
| 4. |
- Decker, J., et al.
(författare)
-
Modelling of LHCD at various densities in tore supra tokamak
- 2012
-
Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics; Stockholm; Sweden; 2 July 2012 through 6 July 2012; Code 96757. - 9781622769810 ; 2, s. 934-937
-
Konferensbidrag (refereegranskat)
|
|
| 5. |
- Dumont, R.J., et al.
(författare)
-
Advances in multi-megawatt, long pulse operation in Tore Supra
- 2012
-
Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics; Stockholm; Sweden; 2 July 2012 through 6 July 2012; Code 96757. - 9781622769810 ; 2, s. 1118-1121
-
Konferensbidrag (refereegranskat)
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Garzotti, L., et al.
(författare)
-
Simulations of density profiles in JET hybrid discharges
- 2012
-
Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics; Stockholm; Sweden; 2 July 2012 through 6 July 2012; Code 96757. - 9781622769810 ; 1, s. 157-160
-
Konferensbidrag (refereegranskat)
|
|
| 9. |
- Hellsten, Torbjörn, et al.
(författare)
-
Self-consistent ICRH modelling
- 2012
-
Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics. - 9781622769810 ; , s. 1106-1109
-
Konferensbidrag (refereegranskat)
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
- Kazakov, Yevgen, 1984, et al.
(författare)
-
Test particle modelling of impurity collisional transport in tokamaks
- 2012
-
Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics; Stockholm; Sweden; 2 July 2012 through 6 July 2012; Code 96757. - 9781622769810 ; 1, s. 229-232
-
Konferensbidrag (refereegranskat)
|
|
| 13. |
|
|
| 14. |
|
|
| 15. |
|
|
| 16. |
- Nyqvist, Robert, 1983, et al.
(författare)
-
Non-monotonic frequency sweeping of fast particle driven instabilities
- 2012
-
Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics; Stockholm; Sweden; 2 July 2012 through 6 July 2012. - 9781622769810 ; 1, s. 619-622
-
Konferensbidrag (refereegranskat)
|
|
| 17. |
- Rasch, Joel, 1982, et al.
(författare)
-
Microwave breakdown due to heating of an irradiated metal sphere
- 2012
-
Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics; Stockholm; Sweden; 2 July 2012 through 6 July 2012; Code 96757. - 9781622769810 ; 3, s. 1907-1910
-
Konferensbidrag (refereegranskat)
|
|
| 18. |
|
|
| 19. |
- Scheffel, Jan, 1954-, et al.
(författare)
-
Resistive pressure driven RFP modes are not removed by heat conduction effects
- 2012
-
Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics. - 9781622769810 ; , s. 1690-1693
-
Konferensbidrag (refereegranskat)abstract
- During the last decade it has been shown theoretically, numerically and experimentally that current driven, resistive tearing modes can be significantly suppressed in the reversed-field pinch (RFP). In these advanced scenarios, the confinement time can be enhanced by a factor 5-10. Pressure driven resistive instabilities (g-modes) still stand in the way, however, for high RFP confinement. Classical theory [1] shows that the unfavourable RFP curvature inevitably leads to unacceptably large linear growth rates even at high Lundquist numbers. Later theory [2] demonstrates, however, that the classical assumption of adiabatic plasma energy dynamics is inaccurate. The reason is that anomalously large experimental perpendicular heat conduction, together with strong parallel heat conduction, to a certain extent outbalance the pressure terms of the plasma energy equation. Resulting resistive length scales appear to extend the resistive layer at the resonance to allow for fully stable, finite beta RFP configurations. In the present work we show theoretically that the latter result is limited to low beta only and that it scales unfavourably with Lundquist number. Numerical solution, using a novel time-spectral method [3] of the linearised resistive MHD initial-value equations including heat conduction, ohmic heating and resistivity, supports the analytical results
|
|
| 20. |
- Voitsekhovitch, I., et al.
(författare)
-
Integrated modelling for tokamak plasma: Physics and scenario optimisation
- 2012
-
Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics; Stockholm; Sweden; 2 July 2012 through 6 July 2012; Code 96757. - 9781622769810 ; 2, s. 1314-1317
-
Konferensbidrag (refereegranskat)abstract
- Simulations of JET and AUG HS with the GLF23 model show that the observed core confinement improvement can be partly explained by the beneficial s/q effect on the ITG driven transport while the effect of the ExB shear stabilisation is weaker than in H-mode plasmas. Strong stabilising effect of βe on the ITG turbulence has been found, but the transport reduction due to this effect can be limited by the onset of the KBM mode at high βe. The simulations of toroidal rotation in HS with the GLF23 model give an indication of the toroidal momentum pinch (Pr
|
|
| 21. |
- Wauters, T., et al.
(författare)
-
Hydrogen ion cyclotron wall conditioning for fuel removal on TEXTOR and ASDEX upgrade
- 2012
-
Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics. - 9781622769810 ; , s. 1378-1381
-
Konferensbidrag (refereegranskat)abstract
- Ion Cyclotron Wall Conditioning (ICWC), applicable in presence of the toroidal magnetic field, is envisaged in ITER to recover from disruptions, leaks and torus vents, for recycling control and for fuel removal. Various experiments on different devices as well as modeling efforts are advancing to consolidate this technique. This contribution focuses on a selection of recent hydrogen ICWC experiments on ASDEX Upgrade and TEXTOR. The ASDEX Upgrade experiment aimed at comparing isotopic exchange efficiencies previously obtained on Carbon devices to the ITER relevant Tungsten wall. The experiment on TEXTOR aimed at assessing the performance of H2-ICWC for codeposited layer removal. The latter being a particular important fuel removal aspect since it is predicted that a major part of tritium in-vessel inventory build-up on ITER will be due to the formation of tritium rich codeposited layers.
|
|
| 22. |
|
|
