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Ion cyclotron resonance heating (ICRH), one of the main auxiliary methods, for high-power and long-pulse plasma heating had been developed in Experimental Advanced Superconducting Tokamak (EAST). An impedance matching system, one important part of ICRH, had been developed for high-power injection and transmitter protection by reducing the reflected power from the antenna. The input impedance in the outlet of the stub tuner can be measured by voltage–current probes installed on the coaxial transmission line between the antenna and triple liquid stub tuners, and the optimum liquid levels in the stub tuners can be calculated based on the input impedance. The calculation and adjustment process of the optimum liquid levels are described comprehensively in this article. Finally, impedance matching had been achieved between two shots during EAST experiments. In the near future, a real-time impedance matching system will be developed to prevent large variations of the ICRH antenna impedance and achieve steady-state and long-pulse operation with the ICRH system. [ABSTRACT FROM AUTHOR]

A coupling model for the waves in ion cyclotron resonance frequency (ICRF) in tokamak plasmas is described. The simulation is performed based on the finite element method. A cold plasma dielectric tensor is used. A perfectly matched layer (PML) is applied to describe the ICRF wave single-pass absorption in the core plasma. The selection of PML characteristic parameters is optimized in a wide wave frequency range and validated for plane waves and ICRF waves. The dependencies of the coupling resistance on the plasma-antenna gap, average plasma density, and plasma profiles are given. The simulation results are in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Chinese Academy of Sciences Institute of Plasma Physics and Massachusetts Institute of Technology Plasma Science and Fusion Center have been collaborating on experimental advanced superconducting tokamak (EAST). Presented in this paper are RF, disruption, and thermal stress analyses of EAST antennas. Analyzed are I port four-strap and B port $2 \times 2$ strap antennas, which are currently installed on EAST. As for RF analysis, scattering parameters are checked to make sure that the antennas are loaded, and then electric field parallel to magnetic field are checked to find out if they are below the permissible level. As for disruption analysis, mechanical stresses for both straps with the support box and Faraday screen are obtained. As for thermal stress analysis, temperature and thermal stress for a typical strap and a Faraday tube were presented. All analyses were performed by COMSOL commercial finite-element analysis software package version 5 or 5.2. [ABSTRACT FROM AUTHOR]

An ion cyclotron range of frequencies (ICRF) system with power up to 6.0MW and a lower hybrid current drive (LHCD) system up to 4MW have been applied for heating and current drive experiments in Experimental Advanced Superconducting Tokomak (EAST). Significant progress has been made with ICRF heating and LHCD for realizing the H-mode plasma operation in EAST. During 2010 and 2012 experimental campaigns, ICRF heating experiments were carried out at the fixed frequency of 27MHz, achieving effective ions and electrons heating with the H minority heating (H-MH) mode. The H-MH mode produced good plasma performance, and realized H-mode using ICRF power alone in 2012. In 2010, H-modes were generated and sustained by LHCD alone, where lithium coating and gas puffing near the mouth of the LH launcher were applied to improve the LHCD power coupling and penetration into the core plasmas of H-modes. In 2012, the combination of LHCD and ICRH power extended the H-mode duration up to over 30 s. H-modes with various types of edge localized modes (ELMs) have been achieved with HIPB98(y, 2) ranging from 0.7 to over unity. A brief overview of LHCD and ICRF Heating experiment and their application in achieving H-mode operation during these two campaigns will be presented. [ABSTRACT FROM AUTHOR]

A long-pulse high confinement plasma regime known as H-mode is achieved in the Experimental Advanced Superconducting Tokamak (EAST) with a record duration over 30 s, sustained by Lower Hybrid wave Current Drive (LHCD) with advanced lithium wall conditioning and divertor pumping. This long-pulse H-mode plasma regime is characterized by the co-existence of a small Magneto-Hydrodynamic (MHD) instability, i.e., Edge Localized Modes (ELMs) and a continuous quasi-coherent MHD mode at the edge. We find that LHCD provides an intrinsic boundary control for ELMs, leading to a dramatic reduction in the transient power load on the vessel wall, compared to the standard Type I ELMs. LHCD also induces edge plasma ergodization, broadening heat deposition footprints, and the heat transport caused by ergodization can be actively controlled by regulating edge plasma conditions, thus providing a new means for stationary heat flux control. In addition, advanced tokamak scenarios have been newly developed for high-performance longpulse plasma operations in the next EAST experimental campaign. [ABSTRACT FROM AUTHOR]

High-performance and long-pulse operation is a crucial goal of current magnetic fusion research. Here, we demonstrate a high-confinement plasma regime known as an H-mode with a record pulse length of over 30 s in the Experimental Advanced Superconducting Tokamak sustained by lower hybrid wave current drive (LHCD) with advanced lithium wall conditioning. We find that LHCD provides a flexible boundary control for a ubiquitous edge instability in H-mode plasmas known as an edge-localized mode, which leads to a marked reduction in the heat load on the vessel wall compared with standard edge-localized modes. LHCD also induces edge plasma ergodization that broadens the heat deposition footprint. The heat transport caused by this ergodization can be actively controlled by regulating the edge plasma conditions. This potentially offers a new means for heat-flux control, which is a key issue for next-step fusion development. [ABSTRACT FROM AUTHOR]

Plasma heating using fast waves was successfully performed on the Experimental Advanced Superconducting Tokamak (EAST) in the H minority regime in deuterium plasmas at 27MHz and Bo = 2.0 T. With 1.0MW of ion cyclotron range of frequency (ICRF) power injected at a line-averaged electron density of 4.0 × 1019 m-3, the electron temperature increased from 1.0 keV to above 2.0 keV and the loop voltage dropped. An increase in the stored energy by 30 kJ was obtained. The first H-mode plasma of 6.4 s was achieved with a combination of lower hybrid wave and ICRF heating. Density pump-out was observed during L-mode discharges at a high electron density of 4.0 × 1019 m-3. In these discharges, re-attachment of the plasma was observed when ICRF power was applied. [ABSTRACT FROM AUTHOR]

Using a 2 MW 2.45 GHz lower hybrid wave (LHW) system installed in experimental advanced superconducting tokamak, we have systematically carried out LHW-plasma coupling and lower hybrid current drive experiments in both divertor (double null and lower single null) and limiter plasma configuration with plasma current (Ip) ∼ 250 kA and central line averaged density (ne) ∼ 1.0-1.3 × 1019 m-3 recently. Results show that the reflection coefficient (RC) first is flat up to some distance between plasma and LHW grill, and then increases with the distance. Studies indicate that with the same plasma parameters, the best coupling is obtained in the limiter case (with plasma leaning on the inner wall), followed by the lower single null, and the one with the worst coupling is the double null configuration, explained by different magnetic connection length. The RCs in the different poloidal rows show that they have different coupling characteristics, possibly due to local magnetic connection length. Current drive efficiency has been investigated by a least squares fit with N//peak=2.1, where N//peak is the peak value of parallel refractive index of the launched wave. Results show that there is no obvious difference in the current drive efficiency between double null and lower single null cases, whereas the efficiency is somewhat small in the limiter configuration. This is in agreement with the ray tracing/Fokker-Planck code simulation by LUKE/C3PO and can be interpreted by the power spectrum up-shift factor in different plasma configurations. A transformer recharge is realized with ∼0.8 MW LHW power and the energy conversion efficiency from LHW to poloidal field energy is about 2%. [ABSTRACT FROM AUTHOR]

Significant progress has been made on the HT-7 superconducting tokamak (R = 1.22 m, a = 0.27 m) in the past year toward obtaining advanced operating modes in steady state. By combining ion Bernstein wave and lower hybrid current drive edge-localized-mode-free limiter H-mode discharges with H[SUB89] ∼ 2, β[SUBN]*H[SUB89]>3 have been obtained that lasted for 53 τ[SUBE]. A well-boronized wall prevented further impurity accumulation and the large pumping kept the recycling at a very low level. The density was kept almost constant with the feedback control. The noninductive driven current fraction is about 60% and bootstrap fraction is about 18%. The central electron temperature is about 2.6 keV and density above 2 × 10[SUP19]m[SUP-3]. With reduced plasma parameters of central Te ∼ 1.5 keV and n[SUBe0] ∼ 2 × 10[SUP19]m[SUP-3], H[SUB89] ∼ 1.45, β[SUBN] ∼ 1.1, the improved confinement phase lasts for more than 100 τ[SUBE] with the noninductive driven current fraction ∼ 70%. [ABSTRACT FROM AUTHOR]

The density profiles were measured in the Hefei tokamak-7 (HT-7) [World Survey of Activities in Controlled Fusion Research, Nuclear Fusion Special Supplement (International Atomic Energy Agency, Vienna, 1997), p. 61] ohmic discharges by means of a new multichannel far-infrared (FIR) laser interferometer. The progress on the extension of the HT-7 ohmic discharge operation region was introduced. The experiment results at the density limit, the multifaceted asymmetric radiation from the edge (MARFE) phenomena, the rf (radio frequency) boronization experiments, and the fueling efficiency studies were reported. The plasma physics in the molecular beam injection (MBI), the pellet injection (PI), and the gas puffing (GP) fueling experiments was studied and discussed. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]