The potential role of magnetic shear, rational safety factor surfaces and shearing rate on the confinement is investigated on the basis of a database analysis of JET internal transport barriers (ITBs). The ITB is quantified using the JET ITB criterion (Tresset G et al 2002 Nucl. Fusion 42 520). The relation between the shearing rate and the magnetic shear, already established for positive magnetic shear barrier (Tala T J J et al 2001 Plasma Phys. Control. Fusion 43 507), is investigated at low and negative magnetic shear, where the threshold in shearing rate is found to be lower than for positive magnetic shear barriers. Defining the ITB from the departure from profile stiffness is found to be consistent with the database results, and the critical gradient length is found to be minimum at low magnetic shear. Finally, ITBs are found to be localized in the vicinity of integer safety factor surfaces in positive magnetic shear plasmas, whereas no correlation is found with integer values when the barrier is localized in negative magnetic shear regions.
All Science Journal Classification (ASJC) codes
- Nuclear Energy and Engineering
- Condensed Matter Physics
Maget, P., Esposito, B., Joffrin, E., Hawkes, N., Mazon, D., Baranov, Y., ... Hoang, G. T. (2003). Statistical analysis of internal transport barriers in JET. Plasma Physics and Controlled Fusion, 45(8), 1385 - 1398. https://doi.org/10.1088/0741-3335/45/8/301