Evidence for modified transport due to sheared E x B flows in high-temperature plasmas
- General Atomics, San Diego, CA (United States)
- Univ. of Maryland, College Park, MD (United States); and others
Sheared mass flows are generated in many fluids and are often important for the dynamics of instabilities in these fluids. Similarly, large values of the E x B velocity have been observed in magnetic confinement machines and there is theoretical and experimental evidence that sufficiently large shear in this velocity may stabilize important instabilities. Two examples of this phenomenon have been observed in the DIII-D tokamak. In the first example, sufficient heating power can lead to the L-H transition, a rapid improvement in confinement in the boundary layer of the plasma. For discharges with heating power close to the threshold required to get the transition, changes in the edge radial electric field are observed to occur prior to the transition itself. In the second example, certain classes of discharges with toroidal momentum input from neutral beam injection exhibit a further improvement of confinement in the plasma core leading to a regime called the VH-mode. In both examples, the region of improved confinement is characterized by an increase of shear in the radial electric field E{sub r}, reduced levels of turbulence and increases in gradients of temperatures and densities. These observations are consistent with the hypothesis that the improved confinement is caused by an increase in shear of the E x B velocity which leads to a reduction of turbulence. For the VH-mode, the dominant term controlling E{sub r} is the toroidal rotation v{sub {phi}}, indicating that the E{sub r} profile is controlled by the source and transport of toroidal momentum.
- Research Organization:
- General Atomics, San Diego, CA (United States); Oak Ridge National Lab., TN (United States); Sandia National Labs., Albuquerque, NM (United States); California Univ., Los Angeles, CA (United States); Massachusetts Inst. of Tech., Cambridge, MA (United States). Plasma Fusion Center; Lawrence Livermore National Lab., CA (United States); California Univ., Los Angeles, CA (United States). Dept. of Physics
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-89ER51114; AC05-84OR21400; AC04-76DP00789; FG03-86ER53225; FG02-91ER54109; W-7405-ENG-48; FG03-89ER51121
- OSTI ID:
- 10108970
- Report Number(s):
- GA-A-21872; CONF-9410249-2; ON: DE95004870; BR: 35AT10020/35AT15040; AT051013C/AT0520210; AT0500000/AT0520210; AT101014Z; TRN: AHC29507%%124
- Resource Relation:
- Conference: ICPP 1994: international conference on plasma physics,Foz do Igacu (Brazil),31 Oct - 4 Nov 1994; Other Information: PBD: Nov 1994
- Country of Publication:
- United States
- Language:
- English
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