Reciprocating probe data taken in the edge and SOL of the TCV tokamak shows ubiquitous intermittent events, caused by coherent filamentary objects moving convectively. The filament motion, which is due to Grad - B charge separa tion can result in significant broadening of the SOL and the formation of a density shoulder, which results in increased plasma - wall contact. Predictive modelling for future fusion devices requires testing of the theoretical models before reliable estimates of the SOL width can be generated. Conditio nal averaging techniques were applied to extract the filaments from the background turbulence and determine filament sizes and velocities. The database we obtained includes density scans in both forward and reverse Bt, with discharges from sheath - limited t o detached regimes. The filaments in TCV were found to range in size from a few mm ( due to the minimum resolution from pin separatio n) to the size of the SOL width and r adial velocities varied from 0 to 6 km/s . Near the LCFS, the poloidal velocity determined using poloidal cross - correlation were typically 5 - 10 km/s , significantly affecting the size determination . T he filaments span the range 0.05< ? <10, and 0.1< ? <1000 including th e connected ideal - interchange regime, the sheath connected - regime, the resistive x - point regime, and the resistive - ballooning regime in the ? - ? space (normalized collisionality and scale size respectively [1 ] ) The extensiveness of the database allows testing of the velocity scalings (e.g. v ? size 1/2 , v ? size - 2 , v ? ? ) associated to each regime and how they change as the filaments transit ion from one regime to another. The radial velocities statistical spread around the scaling is larger than the measurement uncertainty, indicating physics that is not treated by the existing models such as filament - neutral, filament - plas ma and filament - filament interactions.
Filamentary Transport Scaling Validation across Multiple Theoretical Regimes in the TCV Tokamak
Vianello N;
2017
Abstract
Reciprocating probe data taken in the edge and SOL of the TCV tokamak shows ubiquitous intermittent events, caused by coherent filamentary objects moving convectively. The filament motion, which is due to Grad - B charge separa tion can result in significant broadening of the SOL and the formation of a density shoulder, which results in increased plasma - wall contact. Predictive modelling for future fusion devices requires testing of the theoretical models before reliable estimates of the SOL width can be generated. Conditio nal averaging techniques were applied to extract the filaments from the background turbulence and determine filament sizes and velocities. The database we obtained includes density scans in both forward and reverse Bt, with discharges from sheath - limited t o detached regimes. The filaments in TCV were found to range in size from a few mm ( due to the minimum resolution from pin separatio n) to the size of the SOL width and r adial velocities varied from 0 to 6 km/s . Near the LCFS, the poloidal velocity determined using poloidal cross - correlation were typically 5 - 10 km/s , significantly affecting the size determination . T he filaments span the range 0.05< ? <10, and 0.1< ? <1000 including th e connected ideal - interchange regime, the sheath connected - regime, the resistive x - point regime, and the resistive - ballooning regime in the ? - ? space (normalized collisionality and scale size respectively [1 ] ) The extensiveness of the database allows testing of the velocity scalings (e.g. v ? size 1/2 , v ? size - 2 , v ? ? ) associated to each regime and how they change as the filaments transit ion from one regime to another. The radial velocities statistical spread around the scaling is larger than the measurement uncertainty, indicating physics that is not treated by the existing models such as filament - neutral, filament - plas ma and filament - filament interactions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
