The Scrape Off Layer In Alcator C Mod
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The Scrape-off-layer in Alcator C-Mod
| Author | : James L. Terry |
| Publisher | : |
| Total Pages | : 68 |
| Release | : 2005 |
| Genre | : |
| ISBN | : |
(cont.) Evidence that this turbulent transport may play an important role in the core-plasma density limit is presented. Much lower levels of turbulence and no blobs are observed in the high-field-side scrape-off-layer. For single-null magnetic configurations, plasma in the inboard scrape-off-layer appears to be almost entirely a result of plasma flow along field lines from the low-field side. Strong parallel flows with sensitivity to magnetic topology are found, along with strong evidence for momentum coupling between these scrape-off-layer flows and core toroidal rotation
Particle Transport in the Scrape-off Layer and Its Relationship to Discharge Density Limit in Alcator C-Mod
| Author | : Brian LaBombard |
| Publisher | : |
| Total Pages | : 46 |
| Release | : 2001 |
| Genre | : |
| ISBN | : |
(Cont) Small gradients and larger fluctuation levels with longer correlation times are found outside this region (far SOL). Deff in the near SOL increases strongly with local plasma collisionality normalized to the magnetic connection length. As the discharge density limit is approached, Deff and associated fluctuation levels become large across the entire SOL and cross-field heat convection everywhere exceeds parallel conduction losses, impacting the power balance of the discharge.
Comparison of theoretical models for scrape-off layer widths with data from COMPASS-D, JET and Alcator C-MOD
| Author | : J. W. Connor |
| Publisher | : |
| Total Pages | : 28 |
| Release | : 1998 |
| Genre | : Plasma (Ionized gases) |
| ISBN | : |
Flow Measurements in the Scrape-off Layer of Alcator C-Mod Using Impurity Plumes
| Author | : Sanjay Gangadhara |
| Publisher | : |
| Total Pages | : 20 |
| Release | : 2002 |
| Genre | : |
| ISBN | : |
Accurate measurements of plasma flows in the scrape-off layer (SOL) are a necessary requirement for understanding the physics of tokamak edge plasmas. A system is being developed on Alcator C-Mod for inferring flows parallel (v) and perpendicular (vE x B) to local magnetic field lines from impurity emission patterns ("plumes") generated by local gas injection. Carbon plumes are generated at variable location in the SOL by puffing deuterated ethylene gas (C2D4) through the end of a reciprocating fast-scanning probe. Two intensified CCD cameras are used to record C+1 and C+2 emission patterns simultaneously from near-perpendicular views. Plumes are modeled using a Monte Carlo impurity transport code, from which values for the background flows may be extracted. The sensitivity of the plume structure is investigated for a number of code inputs, including radial electric field (Er) and the neutral launch dynamics. Initial modeling results indicate discrepancies between values of v and Er extracted from the plumes and measurements obtained from probe data. Key words: Alcator C-Mod; Scrape-Off Layer Flows; Plumes.
High-field Side Scrape-off Layer Density Profiles Inferred from D[alpha] Emission on Alcator C-Mod
| Author | : Christopher James Boswell |
| Publisher | : |
| Total Pages | : 26 |
| Release | : 2004 |
| Genre | : |
| ISBN | : |
Measurements from an inner wall mounted scanning Langmuir probe and modelling of D[alpha] emission show a sharp fall-off of plasma density in the inboard private flux region. D[alpha] emission is modelled using a one dimensional space, two dimensional velocity kinetic neutral code in order to track the changes in the density profile while the magnetic topology is changed from single to double null. A sharp density decay is observed to track with the location of the secondary separatrix. The presented data is consistent with a lower level of cross-field transport on field lines in the private flux region restricted to the high-field side when compared to cross-field transport on field lines in the low-field side scrape-off layer.
Plasma Profiles and Flows in the High-field Side Scrape-off Layer in Alcator C-Mod
| Author | : Noah M. Smick |
| Publisher | : |
| Total Pages | : 28 |
| Release | : 2004 |
| Genre | : |
| ISBN | : |
A novel, magnetically-driven swing probe was recently installed near the midplane on the high-field side SOL in Alcator C-Mod. The probe collects plasma from co- and counter-current directions during its respective 0-90 and 90-180 degrees of motion, thus providing profiles of density, electron temperature and plasma flow parallel to magnetic field lines (Mach number ... ) up to the separatrix. Results are reported from discharges with different magnetic topologies: lower single-null, upper single-null, and double-null. In single-null, a strong parallel flow ( ... M ...~ 1) is detected, which is always directed from the low- to high-field SOL. In double-null discharges, e-folding lengths in the high-field SOL are a factor of ~4 shorter than the low-field SOL. Thus, plasma appears to 'fill-in' the high-field SOL in single-null plasmas, not by cross-field transport but by parallel flow from the low-field SOL -- a picture consistent with a very strong ballooning-like component to the cross-field transport.
