Change search
ReferencesLink to record
Permanent link

Direct link
The formation and evolution of extreme shear reversal in JET and its influence on local thermal transport
Show others and affiliations
2002 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 44, no 7, 1105-1125 p.Article in journal (Refereed) Published
Abstract [en]

In JET discharges where lower hybrid heating and current drive (LHCD) is applied early during the current ramp, a region of the plasma with zero current density is formed near the axis. At the boundary of this region the current density is large and B-theta increases rapidly over a small distance. In the central region the safety factor, q, is effectively infinite, but this falls steeply in the boundary region. Outside the boundary region q reaches a minimum, where the magnetic shears equivalent to r/q (dq/dr) becomes zero. The formation of this region of zero current is dependent on both the heating and the current drive effects of the LHCD. When LHCD is switched off the current profile begins to relax towards the resistive peaked current distribution of fully inductive tokamak operation. If LHCD is not used in the current rise then these current profiles are not established. Although the physical mechanism exists to drive the central plasma current below zero, in most cases it appears to be prevented from going negative. At least one MHD mechanism has been identified which could be responsible for this. The presence of the zero central current is closely linked to the periodic relaxation events seen in these discharges. In these discharges, internal transport barriers have been observed with additional heating powers substantially below the values required to obtain barriers in monotonic q profile cases.

Place, publisher, year, edition, pages
2002. Vol. 44, no 7, 1105-1125 p.
Keyword [en]
magnetic shear, tokamaks, performance, discharges, stability, barriers, plasmas, tftr
URN: urn:nbn:se:kth:diva-21788ISI: 000177271400006OAI: diva2:340486
QC 20100525Available from: 2010-08-10 Created: 2010-08-10Bibliographically approved

Open Access in DiVA

No full text

Search in DiVA

By author/editor
Rachlew, Elisabeth
By organisation
In the same journal
Plasma Physics and Controlled Fusion

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 15 hits
ReferencesLink to record
Permanent link

Direct link