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flow divertor

Santanu Banerjee, H Zushi, N Nishino, K Mishra, T Onchi, A Kuzmin, Y Nagashima, K Hanada, K Nakamura, H Idei, M Hasegawa, A Fujisawa
An orthogonal dynamic programming (ODP) based particle image velocimetry (PIV) technique is developed to measure the time resolved flow field of the fluctuating structures at the plasma edge and scrape off layer (SOL) of tokamaks. This non-intrusive technique can provide two dimensional velocity fields at high spatial and temporal resolution from a fast framing image sequence and hence can provide better insights into plasma flow as compared to conventional probe measurements. Applicability of the technique is tested with simulated image pairs...
March 2015: Review of Scientific Instruments
S A Silburn, J R Harrison, J Howard, K J Gibson, H Meyer, C A Michael, R M Sharples
A new coherence imaging Doppler spectroscopy diagnostic has been deployed on the UK's Mega Amp Spherical Tokamak for scrape-off-layer and divertor impurity flow measurements. The system has successfully obtained 2D images of C III, C II, and He II line-of-sight flows, in both the lower divertor and main scrape-off-layer. Flow imaging has been obtained at frame rates up to 1 kHz, with flow resolution of around 1 km/s and spatial resolution better than 1 cm, over a 40° field of view. C III data have been tomographically inverted to obtain poloidal profiles of the parallel impurity flow in the divertor under various conditions...
November 2014: Review of Scientific Instruments
Y Liang, X Z Gong, K F Gan, E Gauthier, L Wang, M Rack, Y M Wang, L Zeng, P Denner, A Wingen, B Lv, B J Ding, R Chen, L Q Hu, J S Hu, F K Liu, Y X Jie, J Pearson, J P Qian, J F Shan, B Shen, T H Shi, Y Sun, F D Wang, H Q Wang, M Wang, Z W Wu, S B Zhang, T Zhang, X J Zhang, N Yan, G S Xu, H Y Guo, B N Wan, J G Li
Strong mitigation of edge-localized modes has been observed on Experimental Advanced Superconducting Tokamak, when lower hybrid waves (LHWs) are applied to H-mode plasmas with ion cyclotron resonant heating. This has been demonstrated to be due to the formation of helical current filaments flowing along field lines in the scrape-off layer induced by LHW. This leads to the splitting of the outer divertor strike points during LHWs similar to previous observations with resonant magnetic perturbations. The change in the magnetic topology has been qualitatively modeled by considering helical current filaments in a field-line-tracing code...
June 7, 2013: Physical Review Letters
T R Weber, S L Allen, J Howard
This work describes a coherence imaging spectrometer capable of making spatially resolved CIII flow measurements in the DIII-D lower divertor. The spectrometer exploits a periscope view of the plasma to produce line-of-sight averaged velocity measurements of CIII. From these chord averaged flow measurements, a 2D poloidal cross section of the CIII flow is tomographically reconstructed. Details of the diagnostic setup, acquired data, and data analysis will be presented, along with prospects for future applications...
October 2012: Review of Scientific Instruments
R J Perkins, J C Hosea, G J Kramer, J-W Ahn, R E Bell, A Diallo, S Gerhardt, T K Gray, D L Green, E F Jaeger, M A Jaworski, B P LeBlanc, A McLean, R Maingi, C K Phillips, L Roquemore, P M Ryan, S Sabbagh, G Taylor, J R Wilson
A significant fraction of high-harmonic fast-wave (HHFW) power applied to NSTX can be lost to the scrape-off layer (SOL) and deposited in bright and hot spirals on the divertor rather than in the core plasma. We show that the HHFW power flows to these spirals along magnetic field lines passing through the SOL in front of the antenna, implying that the HHFW power couples across the entire width of the SOL rather than mostly at the antenna face. This result will help guide future efforts to understand and minimize these edge losses in order to maximize fast-wave heating and current drive...
July 27, 2012: Physical Review Letters
D Brunner, B LaBombard
A novel set of thermocouple sensors has been developed to measure heat fluxes arriving at divertor surfaces in the Alcator C-Mod tokamak, a magnetic confinement fusion experiment. These sensors operate in direct contact with the divertor plasma, which deposits heat fluxes in excess of ~10 MW/m(2) over an ~1 s pulse. Thermoelectric EMF signals are produced across a non-standard bimetallic junction: a 50 μm thick 74% tungsten-26% rhenium ribbon embedded in a 6.35 mm diameter molybdenum cylinder. The unique coaxial geometry of the sensor combined with its single-point electrical ground contact minimizes interference from the plasma/magnetic environment...
March 2012: Review of Scientific Instruments
F L Tabarés, J A Ferreira, A Ramos, G van Rooij, J Westerhout, R Al, J Rapp, A Drenik, M Mozetic
A technique based on reactive gas injection in the afterglow region of the divertor plasma is proposed for the suppression of tritium-carbon codeposits in remote areas of ITER when operated with carbon-based divertor targets. Experiments in a divertor simulator plasma device indicate that a 4  nm/min deposition can be suppressed by addition of 1  Pa·m³ s⁻¹ ammonia flow at 10 cm from the plasma. These results bolster the concept of nonperturbative scavenger injection for tritium inventory control in carbon-based fusion plasma devices, thus paving the way for ITER operation in the active phase under a carbon-dominated, plasma facing component background...
October 22, 2010: Physical Review Letters
J Howard, A Diallo, M Creese, B D Blackwell, S L Allen, R M Ellis, G D Porter, W Meyer, M E Fenstermacher, N H Brooks, M E Van Zeeland, R L Boivin
This article describes the results of spatial heterodyne Doppler "coherence imaging" of carbon ion flows in the divertor region of the DIII-D tokamak. Spatially encoded interferometric projections of doubly ionized carbon emission at 465 nm have been demodulated and tomographically inverted to obtain the spatial distribution of the carbon ion parallel flow and emissivity. The operating principles of the new instruments are described, and the link between measured properties and line integrals of the flow field are established...
October 2010: Review of Scientific Instruments
A Wingen, T E Evans, C J Lasnier, K H Spatschek
Edge localized modes (ELMs) are qualitatively and quantitatively modeled in tokamaks using current bursts which have been observed in the scrape-off-layer (SOL) during an ELM crash. During the initial phase of an ELM, a heat pulse causes thermoelectric currents. They first flow in short connection length flux tubes which are initially established by error fields or other nonaxisymmetric magnetic perturbations. The currents change the magnetic field topology in such a way that larger areas of short connection length flux tubes emerge...
April 30, 2010: Physical Review Letters
A G McLean, J W Davis, P C Stangeby, N H Brooks, R M Ellis, A A Haasz, D L Rudakov, W P West, D G Whyte, C P C Wong
A probe has been designed, constructed, and successfully used to inject methane into the DIII-D lower divertor in a manner imitating natural release by chemical erosion. This porous plug injector (PPI) probe consists of a self-contained gas reservoir with an integrated pressure gauge and a 3 cm diameter porous surface through which gas is injected into the lower divertor of the tokamak. The probe is positioned flush with the divertor target surface by means of the divertor materials evaluation system. Two gas delivery systems were developed: in the first, gas flow is regulated by a remotely controlled microvalve and in the second by a fixed micro-orifice flow restrictor...
April 2009: Review of Scientific Instruments
Jaehoon Seong, Ajay K Wakhloo, Baruch B Lieber
Endovascular coiling is an acceptable treatment of intracranial aneurysms, yet long term follow-ups suggest that endovascular coiling fails to achieve complete aneurysm occlusions particularly in wide-neck and giant aneurysms. Placing of a stentlike device across the aneurysm neck may be sufficient to occlude the aneurysm by promoting intra-aneurysmal thrombosis; however, conclusive evidence of its efficacy is still lacking. In this study, we investigate in vitro the efficacy of custom designed flow divertors that will be subsequently implanted in a large cohort of animals...
December 2007: Journal of Biomechanical Engineering
Chander Sadasivan, Baruch B Lieber, Liliana Cesar, Laszlo Miskolczi, Jaehoon Seong, Ajay K Wakhloo
Past clinical and experimental evidence suggests that cerebral aneurysms can be successfully excluded from the circulation solely by the endovascular placement of a flow diverting device across the aneurysm neck. These devices promote intraaneurysmal flow stasis and concomitant thrombosis by redirecting flow away from the aneurysm. To comprehensively test the efficacy of such flow divertors, we are implanting devices with three different porosities in a large cohort of elastase-induced aneurysms in rabbits...
2006: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Y Xu, R R Weynants, S Jachmich, M Van Schoor, M Vergote, P Peleman, M W Jakubowski, M Mitri, D Reiser, B Unterberg, K H Finken et al.
Systematic measurements on the edge turbulence and turbulent transport have been made by Langmuir probe arrays on TEXTOR under various static Dynamic Ergodic Divertor (DED) configurations. Common features are observed. With the DED, in the ergodic zone the local turbulent flux reverses sign from radially outwards to inwards. The turbulence properties are profoundly modified by energy redistribution in frequency spectra and suppression of large scale eddies. The fluctuation poloidal phase velocity changes direction from electron to ion diamagnetic drift, consistent with the observed reversal of the Er x B flow...
October 20, 2006: Physical Review Letters
Asakura, Sakurai, Shimada, Koide, Hosogane, Itami
The plasma profile and parallel plasma flow in the scrape-off layer (SOL) were systematically measured using reciprocating Mach probes installed at the outer midplane and near the divertor magnetic null (x point) in the JT-60U tokamak with a single null divertor. For the ion vertical drift due to the toroidal magnetic field gradient (ion nablaB drift) directed towards the divertor, SOL plasma flow along the magnetic field lines away from the divertor ("flow reversal") was discovered at the midplane far from the divertor...
April 3, 2000: Physical Review Letters
Heikkinen, Kiviniemi, Peeters
Monte Carlo ion simulation based on neoclassical radial current balance in a divertor tokamak gives a stationary sheared E-->xB--> flow. The neoclassical radial electric field E(r) shows no bifurcation in contrast with earlier orbit loss models, but the shear in E(r) reaches values at which a transition to enhanced confinement has been observed. Also, MHD turbulence analysis shows that a smooth transition can occur through the neoclassical E-->xB--> flow shear suppression. The parameter scaling of threshold temperature for strong turbulence shear suppression agrees with the H-mode threshold scaling in ASDEX Upgrade...
January 17, 2000: Physical Review Letters
Bosch, Dux, Haas, Kallenbach, Kaufmann, Lackner, Mertens, Murmann, Poschenrieder, Salzmann, Schweinzer, Suttrop, Weinlich
No abstract text is available yet for this article.
April 1, 1996: Physical Review Letters
Doerner, Anderson, Hitchon, Matthews, Shohet
No abstract text is available yet for this article.
January 9, 1989: Physical Review Letters
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