Observations of anomalous momentum transport in Alcator C-Mod plasmas with no momentum input

被引：116

作者：

Rice, JE ^{[1
]}

Lee, WD ^{[1
]}

Marmar, ES ^{[1
]}

Bonoli, PT ^{[1
]}

Granetz, RS ^{[1
]}

Greenwald, MJ ^{[1
]}

Hubbard, AE ^{[1
]}

Hutchinson, IH ^{[1
]}

Irby, JH ^{[1
]}

Lin, Y ^{[1
]}

Mossessian, D ^{[1
]}

Snipes, JA ^{[1
]}

Wolfe, SM ^{[1
]}

Wukitch, SJ ^{[1
]}

机构：

[1] MIT, Plasma Sci & Fus Ctr, Cambridge, MA 02139 USA

来源：

NUCLEAR FUSION | 2004年 / 44卷 / 03期

关键词：

D O I：

10.1088/0029-5515/44/3/001

中图分类号：

O35 [流体力学]; O53 [等离子体物理学];

学科分类号：

070204 ; 080103 ; 080704 ;

摘要：

Anomalous momentum transport has been observed in Alcator C-Mod tokamak plasmas. The time evolution of core impurity toroidal rotation velocity profiles has been measured with a tangentially viewing crystal x-ray spectrometer array. Following the L-mode to EDA (enhanced D-alpha) H-mode transition in both Ohmic and ion cyclotron range of frequencies heated discharges, the ensuing co-current toroidal rotation velocity, which is generated in the absence of any external momentum source, is observed to propagate in from the edge plasma to the core with a timescale of the order of the observed energy confinement time, but much less than the neo-classical momentum confinement time. The ensuing steady state toroidal rotation velocity profiles in EDA H-mode plasmas are relatively flat, with V-phi similar to 50 km s(-1), and the momentum transport can be simulated using a simple diffusion model. Assuming that the L-H transition produces an instantaneous edge source of toroidal torque (which disappears at the H- to L-mode transition), the momentum transport may be characterized by a diffusivity, with values of similar to0.07 m(2) s(-1) during EDA H-mode and similar to0.2 m(2) s(-1) in L-mode. These values are large compared to the calculated neo-classical momentum diffusivities, which are of the order of 0.003 m(2) s(-1). Velocity profiles of ELM-free H-mode plasmas are centrally peaked (with V-phi(0) exceeding 100 km s(-1) in some cases), which suggests the presence of an inward momentum pinch; the observed profiles are consistent with simulations including an edge inward convection velocity of similar to10 m s(-1). In EDA H-mode discharges which develop internal transport barriers, the velocity profiles become hollow in the centre, indicating the presence of a negative radial electric field well in the vicinity of the barrier foot. Upper single null diverted and inner wall limited L-mode discharges exhibit strong counter-current rotation (with V-phi(0)similar to-60 km s(-1) in some cases), which may be related to the observed higher H-mode power threshold in these configurations. For plasmas with locked modes, the toroidal rotation is observed to cease (V-phi less than or equal to 5 km s(-1)).

引用

页码：379 / 386

页数：8

共 47 条

[1] TOROIDAL ROTATION AND ION HEATING DURING NEUTRAL BEAM INJECTION IN PBX-M [J].