Internal transport barrier with improved confinement in the JT-60U tokamak

Abstract

Characteristics of the internal transport barrier (ITB) were studied. The region of steep ∇T i and ∇V t , i.e. the ITB front, propagated from the core outwards. The thickness of the ITB front was about 3 cm. The ITB worked as a particle transport barrier as well as a thermal transport barrier for ions. The threshold heating power for ITB formation strongly increased with electron density and was independent of the toroidal magnetic field. ITB with τ E /τ ITER89-P E ≈ 2.6 was sustained for twice the global energy confinement time τ E . A repetitive relaxation phenomenon at ITB was observed, which induced D α spikes like ELMs but had a different poloidal distribution. * This paper is an extended version of a contribution to the 22nd EPS conference on Controlled Fusion and Plasma Physics held in Bournemouth, UK, July 1995.

Formation and structure of internal and edge transport barriers

“…Such qualitatively similar aspects of core and edge barriers are highlighted in Fig High β p modes in JT-60U [Koide, 1996], and electron barriers on RTP [DeBaar, 1997].…”

“…Schilling G et al 1997 Proc.24th [Groebner, 1993] (b) Figure 3. Ion temperature profiles after transitions to enhanced confinement for (a) a High β p mode plasma with a monotonic q profile from JT-60U [Koide, 1996], and (b) a JET Optimized Shear plasma with weak or negative magnetic shear [Sips, 1997b]. For both regimes, the barrier is initiated deep in the core and propagates outward with time.…”

Nonlinear electromagnetic gyrokinetic equation for plasmas with large mean flows

“…In recent years, the effects of large flows have been attracting much attention in relation to improved confinement such as high-confinement modes ͑H-modes͒ 26 and internal transport barriers ͑ITB͒ found in reversed shear configurations. 27, 28 Artun and Tang 6,7 derived the gyrokinetic equations for the slab and toroidal system with large equilibrium flows by using the recursive method for the ballooning type of fluctuations. Hamiltonian derivation of the gyrokinetic equation for the toroidally rotating plasma was shown by Brizard.…”

Gyrokinetic simulations of collisionless reconnection in turbulent non-uniform plasmas

“…The rapid heat transfer due to microtearing may underlie, for example, the sudden collapse of the electron temperature profile during tokamak sawtooth reconnection [17][18][19] or the strong thermal transport associated with internal transport barriers in tokamaks. 20,21 We employ the AstroGK simulation code [22][23][24] which evolves the nonlinear gyrokinetic equations for ions and electrons and the Maxwell equations for A k ; A ? .…”