| 1. |
- Stroth, U., et al.
(författare)
-
Progress from ASDEX Upgrade experiments in preparing the physics basis of ITER operation and DEMO scenario development
- 2022
-
Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 62:4
-
Tidskriftsartikel (refereegranskat)abstract
- An overview of recent results obtained at the tokamak ASDEX Upgrade (AUG) is given. A work flow for predictive profile modelling of AUG discharges was established which is able to reproduce experimental H-mode plasma profiles based on engineering parameters only. In the plasma center, theoretical predictions on plasma current redistribution by a dynamo effect were confirmed experimentally. For core transport, the stabilizing effect of fast ion distributions on turbulent transport is shown to be important to explain the core isotope effect and improves the description of hollow low-Z impurity profiles. The L-H power threshold of hydrogen plasmas is not affected by small helium admixtures and it increases continuously from the deuterium to the hydrogen level when the hydrogen concentration is raised from 0 to 100%. One focus of recent campaigns was the search for a fusion relevant integrated plasma scenario without large edge localised modes (ELMs). Results from six different ELM-free confinement regimes are compared with respect to reactor relevance: ELM suppression by magnetic perturbation coils could be attributed to toroidally asymmetric turbulent fluctuations in the vicinity of the separatrix. Stable improved confinement mode plasma phases with a detached inner divertor were obtained using a feedback control of the plasma β. The enhanced D α H-mode regime was extended to higher heating power by feedback controlled radiative cooling with argon. The quasi-coherent exhaust regime was developed into an integrated scenario at high heating power and energy confinement, with a detached divertor and without large ELMs. Small ELMs close to the separatrix lead to peeling-ballooning stability and quasi continuous power exhaust. Helium beam density fluctuation measurements confirm that transport close to the separatrix is important to achieve the different ELM-free regimes. Based on separatrix plasma parameters and interchange-drift-Alfvén turbulence, an analytic model was derived that reproduces the experimentally found important operational boundaries of the density limit and between L- and H-mode confinement. Feedback control for the X-point radiator (XPR) position was established as an important element for divertor detachment control. Stable and detached ELM-free phases with H-mode confinement quality were obtained when the XPR was moved 10 cm above the X-point. Investigations of the plasma in the future flexible snow-flake divertor of AUG by means of first SOLPS-ITER simulations with drifts activated predict beneficial detachment properties and the activation of an additional strike point by the drifts.
|
|
| 2. |
- Metzler, R., et al.
(författare)
-
Diffusion mechanisms of localised knots along a polymer
- 2006
-
Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 76:4, s. 696-702
-
Tidskriftsartikel (refereegranskat)abstract
- We consider the diffusive motion of a localised knot along a linear polymer chain. In particular, we derive the mean diffusion time of the knot before it escapes from the chain once it gets close to one of the chain ends. Self-reptation of the entire chain between either end and the knot position, during which the knot is provided with free volume, leads to an L-3 scaling of diffusion time; for sufficiently long chains, subdiffusion will enhance this time even more. Conversely, we propose local "breathing", i.e., local conformational rearrangement inside the knot region (KR) and its immediate neighbourhood, as additional mechanism. The contribution of KR-breathing to the diffusion time scales only quadratically, similar to L-2, speeding up the knot escape considerably and guaranteeing finite knot mobility even for very long chains.
|
|
| 3. |
|
|
| 4. |
- Reisner, W, et al.
(författare)
-
The physics of nanoconfined DNA
- 2006
-
Ingår i: Book of abstracts: March Meet of the American Phys Soc, Baltimore, MD, USA (2006).
-
Konferensbidrag (refereegranskat)
|
|
| 5. |
- Reisner, Walter W., et al.
(författare)
-
Melting mapping in nanochannels
- 2008
-
Ingår i: ; , s. 1516-1518
-
Konferensbidrag (refereegranskat)abstract
- We demonstrate direct visualization of melting mapping of DNA stretched in nanoscale channels[1] using standard staining methods and epifluorescence microscopy to gain information on the local AT/GC ratio along large DNA molecules. Our development opens up a novel route to mapping of large-scale genomic variations.
|
|
| 6. |
|
|
