TY - JOUR
T1 - The operational phase-space of the edge plasma and its sensitivity to magnetic topology in Alcator C-Mod
AU - LaBombard, B.
AU - Smick, N.
AU - Greenwald, M.
AU - Hughes, J.W.
AU - Lipschultz, B.
AU - Marr, K.
AU - Terry, J.L.
PY - 2007/6/15
Y1 - 2007/6/15
N2 - The range of 'edge plasma states' (i.e., the combination of densities, temperatures and gradients in the scrape-off layer near the separatrix) accessible to a tokamak are highly restricted. Experiments in Alcator C-Mod suggest that this restriction is a consequence of electromagnetic fluid drift turbulence (EMFDT), which sets the cross-field transport levels; plasma states are constrained to lie in a narrow region of EMFDT 'phase-space' defined by poloidal beta gradient (α) and normalized plasma collisionality. Recent experiments have investigated this behavior over an increased parameter range in lower- and upper-null (LSN/USN) discharges. L-mode edge pressure gradients are found to exhibit clear sensitivity to magnetic topology, favoring higher α for LSN compared to USN. These variations may be caused, in part, by the different edge plasma flow patterns in LSN versus USN. Such flows arise from a ballooning-like transport drive and can produce a topology-dependent modulation in the toroidal plasma rotation.
AB - The range of 'edge plasma states' (i.e., the combination of densities, temperatures and gradients in the scrape-off layer near the separatrix) accessible to a tokamak are highly restricted. Experiments in Alcator C-Mod suggest that this restriction is a consequence of electromagnetic fluid drift turbulence (EMFDT), which sets the cross-field transport levels; plasma states are constrained to lie in a narrow region of EMFDT 'phase-space' defined by poloidal beta gradient (α) and normalized plasma collisionality. Recent experiments have investigated this behavior over an increased parameter range in lower- and upper-null (LSN/USN) discharges. L-mode edge pressure gradients are found to exhibit clear sensitivity to magnetic topology, favoring higher α for LSN compared to USN. These variations may be caused, in part, by the different edge plasma flow patterns in LSN versus USN. Such flows arise from a ballooning-like transport drive and can produce a topology-dependent modulation in the toroidal plasma rotation.
UR - http://www.scopus.com/inward/record.url?scp=34248545644&partnerID=8YFLogxK
U2 - 10.1016/j.jnucmat.2006.12.040
DO - 10.1016/j.jnucmat.2006.12.040
M3 - Article
AN - SCOPUS:34248545644
SN - 0022-3115
VL - 363-365
SP - 517
EP - 521
JO - Journal of Nuclear Materials
JF - Journal of Nuclear Materials
IS - 1-3
ER -