Internal Transport Barrier: Difference between revisions
No edit summary |
No edit summary |
||
| Line 1: | Line 1: | ||
No generally accepted definition for Internal Transport Barriers (ITBs) exists. Vaguely speaking, the term refers to a radially localized reduction of transport for ions or electrons. | No generally accepted definition for Internal Transport Barriers (ITBs) exists. Vaguely speaking, the term refers to a radially localized reduction of transport for ions or electrons. | ||
ITBs can be actively produced by modifying the current profile using external means. | |||
<ref>[http://dx.doi.org/10.1088/0741-3335/45/1/201 R.C. Wolf, ''Internal transport barriers in tokamak plasmas'', Plasma Phys. Control. Fusion '''45''' (2003) R1-R91]</ref> | |||
They are used to improve plasma confinement and stability properties, and to drive additional bootstrap current. Therefore, they are included in some alternative operational scenarios for [[ITER]]. | |||
== Physical mechanism == | == Physical mechanism == | ||
Revision as of 15:41, 27 August 2009
No generally accepted definition for Internal Transport Barriers (ITBs) exists. Vaguely speaking, the term refers to a radially localized reduction of transport for ions or electrons.
ITBs can be actively produced by modifying the current profile using external means. [1] They are used to improve plasma confinement and stability properties, and to drive additional bootstrap current. Therefore, they are included in some alternative operational scenarios for ITER.
Physical mechanism
The mechanism for the formation of Internal Transport Barriers in magnetically confined plasmas is complex and not fully understood. Probably, it is related to the mechanism for the formation of the H-mode barrier, involving turbulence suppression by sheared flows, and possibly associated with rational magnetic surfaces.
Factors contributing to the formation of ITBs include: [2]
- Power deposited inside the magnetic surface, and/or pressure gradients
- Magnetic shear and the shape of the profile of the rotational transform
- MHD activity
- Momentum torques (poloidal or toroidal)