Observation of ELM-free H-mode in the HL-2A tokamak

Abstract

For the first time, edge-localized mode (ELM)-free H-mode was realized in the HL-2A tokamak by using electron cyclotron resonance heating and co-current neutral beam injection (NBI) heating. This ELM-free H-mode is associated with the formation of edge particle transport barrier, an increase in density peaking and a significant decrease in edge turbulence. During the stationary ELM-free phase, an edge magnetohydrodynamic mode is identified, which has similar characteristics to an edge harmonic oscillation (EHO), as observed in other tokamaks. This EHO-like mode enhances edge particle transport, and propagates poloidally in the electron diamagnetic drift direction and toroidally in the same direction as the plasma current and NBI. A detailed analysis of this mode and the EHO-ELM transition is presented in this paper.

Progress of the synthetic HCOOH laser diagnostic system on HL-2A tokamak

“…The auxiliary heating platform includes 2.0 MW neutral beam injection (NBI), 3.0 MW (at 68 GHz) and 2.0 MW (at 140 GHz) electron cyclotron resonance heating (ECRH), and 2.0 MW low hybrid heating (LH) at 3.7 GHz [1]. Recent HL-2A experiments mainly focused on the high-temperature plasma physics [2][3][4], covering the field of Magneto-Hydro-Dynamic (MHD) instability, plasma transport and confinement, energetic-particle-driven instability, turbulence, Divertor physics, and so on. To disclose these physical process, it is crucial to develop high sensitivity diagnostic tool.…”

“…(2) For the Polarimeter, the main interference source of Faraday rotation angle measurement was identified to be the stay light, and preliminary result indicated that the stray light coming from the detector surface can be largely suppressed by using the optic-isolator which was made up of a polarizer and a quarter wave plate. (3) The newly developed Far-forward collective scattering diagnostic based on two circularly polarized waves was widely used to investigate broadband density fluctuations in recent experimental campaign.…”

Overview of recent HL-2A experiments

“…Since the last Fusion Energy Conference, the experiments on the HL-2A tokamak have been focused on the investigation of H-mode related physics, including edge-localized modes (ELM) mitigation and L-H transition mechanism, energetic particle (EP) physics and magnetohydrodynamic (MHD) instabilities, and L-H transition relevant turbulence and zonal flows (ZF), etc. In particular, the first demonstration of converting large ELMs into a series of small ELMs with supersonic molecular beam injection (SMBI) or cluster jet injection (CJI) [3,4], the investigation of toroidicity-induced Alfven eigenmodes (TAEs) and beta-induced Alfven eigenmodes (BAEs) [5,6], ELM-free H-mode and intermediate limit-cycle oscillation (LCO) (I-phase) [7,8], nonlinear energy transfer [9,10], blob generation and its dynamics [11], meso-scale electric fluctuations and turbulence interactions [12] have significantly contributed to the understanding of the underlying physics. The major experimental results are reviewed in this paper while details are described in the corresponding references.…”

Transport Simulation of ECRH H-Mode Experiments on HL-2A Tokamak

“…The ELMy H-mode with NBI heating only was obtained in 2012, and the lowest power is 0.7 MW [2] . The ELM free Hmode was also realized by using ECRH and co-current NBI heating in 2012 [17] . In recent years, researchers, in the group of HL-2A experiments, attempt to achieve H-mode with ECR heating alone.…”