Observation of a Spontaneous Particle-Transport Barrier in the HL-2A Tokamak

Abstract

Using the profile analysis, the density perturbation transport analysis, and the Doppler reflectometry measurement, for the first time a spontaneous and steady-state particle-transport barrier has been evidenced in the Ohmic plasmas in the HL-2A tokamak with no externally applied momentum or particle input except the gas puffing. A threshold in density has been found for the observation of the barrier. The particle diffusivity is well-like, and the convection is found to be inward outside the well and outward inside the well. The formation of the barrier coincides with the transition between the trapped electron mode and the ion temperature gradient driven mode.

Identification of trapped electron modes in frequency fluctuation spectra

“…Thanks to the modulations of radio-frequency heating or to the injection of a particle pulse, the estimation of the transport coefficients can also help to discriminate ITG from TEM dominated regimes. For instance, transition between the dominant instabilities can be inferred from the parametric dependency of the diffusion [6,7] or by a reversal of the convection velocity direction [8,9]. However, both phase velocity and transport coefficient estimations currently used to investigate ITG and TEM are complex and not always feasible as they require advanced diagnostics or specific perturbation experiments scenario.…”

Propagation Dynamics Associated with Resonant Magnetic Perturbation Fields in High-Confinement Mode Plasmas inside the KSTAR Tokamak

“…2(b). In perturbative plasma transport experiments, a minimum phase position generally indicates the position of an induced perturbation source [13,15]. The induced minimum phase in v ϕ is unlikely to be due to a modulation of the "neutral particle source" because SMBI neutral particles cannot penetrate through the edge plasma to reach the q ¼ 3 position, let alone q ¼ 2 positions in KSTAR H-mode discharges [12].…”

A review of supersonic molecular beam injection for plasma fueling and physical studies in magnetic fusion devices

“…A spontaneous particle internal transport barrier (pITB) was first demonstrated in Ohmic plasmas on HL-2A (Xiao et al 2010b). In this experiment, no external momentum input was applied.…”