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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]

Abstract: Arc detection systems are developed for ICRH on ITER to prevent arcs from damaging the ICRF components. One of the detectors, the Sub-Harmonic Arc Detector (SHAD) is based on the detection of the frequencies emitted in the MHz range by arcs , and is consequently resilient to fast load changes. A prototype has been in operation on ASDEX-Upgrade for ten years and has demonstrated its capability to detect arcs. However, to reach the safety level required by ITER, the design has to be modified to eliminate the spurious detections triggered by plasma emission in the MHz range and to enhance the sensitivity to low-voltage arcs. These improvements, which must preserve the simplicity of the system to guarantee its reliability, are based on the experience of RF arcs in resonant structures acquired on ASDEX-Upgrade and on dedicated test-benches. We present the main features of arcs in time and frequency domains and their impact on the behaviour of the SHAD system. Several technological solutions are based on these data and have to support the harsh environment of a burning plasma experiment. The shielding, the location of the detector, the reliability can be affected by the nuclear radiations. These elements are integrated in the design to make of the SHAD a primary safety system for ICRF heating. [Copyright &y& Elsevier]

The characteristics of the magnetized plasma obtained in a modified double-plasma device are presented. Primary ionizing electrons are produced by filament discharges in multipole devices located on either end of a magnetized plasma column. A very uniform magnetized plasma is produced in the column with a relatively small number of filaments by using coils to counterbalance the fringing field near the filaments. The obtained plasma is well suited for a large variety of wave experiments. The noise is maintained at a low level and the afterglow measurements reveal a very efficient confinement of the ionizing electrons, with a decay time of 0.2 ms. [ABSTRACT FROM AUTHOR]

An analysis of the mode conversion of an electrostatic Bernstein wave in a plasma near the upper-hybrid resonance is developed. The conversion coefficients for the reflected extraordinary and electrostatic waves and for the transmitted electromagnetic wave are derived and calculated for various values of the inhomogeneity length and wave frequency. [ABSTRACT FROM AUTHOR]

Abstract: Analysis of the W concentration during ICRF over AUG experimental campaigns confirms the critical role of W antenna limiters for the W content in plasma, though other structures connected to antennas along magnetic field lines cannot be neglected as W sources. Abrupt changes of spectroscopically measured W sputtering patterns are observed which correlate with step-wise changes of connection lengths at antenna limiters. Analysis of discharges with the reversed direction of toroidal magnetic field shows less W release compared to identical discharges with the normal direction. The lower W release is accompanied by lower intensity of fluctuations of reflected ICRF power in the 1–60kHz range. The observations suggest that local magnetic geometry and density convection at the antennas are at least as important for the W sputtering as the distribution of RF near-fields at the antenna. Measurements of DC currents flowing through the antenna limiters show that the limiters at the active antenna collect predominantly negative DC currents whereas those distant from the active antenna collect predominantly positive DC currents. The latter decrease and become more negative when the intensity of the RF pickup measured at the limiters increases. The mutual compensation between the positive and negative currents can lead to lower values of the DC current than those expected from simplified theoretical models of the RF/DC circuit. [Copyright &y& Elsevier]