title: Observation of zero current density in the core of jet discharges with lower hybrid heating and current drive.
abstract: Simultaneous current ramping and application of lower hybrid heating and current drive (LHCD) have produced a region with zero current density within measurement errors in the core ( r/a< or =0.2) of JET tokamak optimized shear discharges. The reduction of core current density is consistent with a simple physical explanation and numerical simulations of radial current diffusion including the effects of LHCD. However, the core current density is clamped at zero, indicating the existence of a physical mechanism which prevents it from becoming negative.
authors.affiliation: Euratom/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB, United Kingdom.
authors.forename: N C
authors.initials: NC
authors.lastname: Hawkes
authors.forename: B C
authors.initials: BC
authors.lastname: Stratton
authors.forename: T
authors.initials: T
authors.lastname: Tala
authors.forename: C D
authors.initials: CD
authors.lastname: Challis
authors.forename: G
authors.initials: G
authors.lastname: Conway
authors.forename: R
authors.initials: R
authors.lastname: DeAngelis
authors.forename: C
authors.initials: C
authors.lastname: Giroud
authors.forename: J
authors.initials: J
authors.lastname: Hobirk
authors.forename: E
authors.initials: E
authors.lastname: Joffrin
authors.forename: P
authors.initials: P
authors.lastname: Lomas
authors.forename: P
authors.initials: P
authors.lastname: Lotte
authors.forename: J
authors.initials: J
authors.lastname: Mailloux
authors.forename: D
authors.initials: D
authors.lastname: Mazon
authors.forename: E
authors.initials: E
authors.lastname: Rachlew
authors.forename: S
authors.initials: S
authors.lastname: Reyes-Cortes
authors.forename: E
authors.initials: E
authors.lastname: Solano
authors.forename: K D
authors.initials: KD
authors.lastname: Zastrow