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The plasma dynamics in a planar coil pulsed inductively coupled plasma system (ICPs) operated in argon is investigated using phase and space resolved optical emission spectroscopy. The measurements show the discharge initiation and E-H transition as the function of time. The results show that there is no delay in the discharge initiation and it starts due to capacitive coupling or in the E-mode. It transits to the H-mode later while the emission has a spike-like feature at the E-H transition i.e. it first achieves high emission which later decreases and finally rises again. The 2D images of the discharge reveal that at the time of high emission, the discharge structure is compact and bright, which later decreases in brightness and becomes diffusive. The results show that the spike like feature decreases with pressure until it finally disappears at the pressure of 600 mTorr. [ABSTRACT FROM AUTHOR]

Fast Wave (FW) heating and electron cyclotron heating (ECH) are used in the DIII-D tokamak to study plasmas with low applied torque and dominant electron heating characteristic of burning plasmas. FW heating via direct electron damping has reached the 2.5 MW level in high performance ELMy H-mode plasmas. In Advanced Inductive (AI) plasmas, core FW heating was found to be comparable to that of ECH, consistent with the excellent first-pass absorption of FWs predicted by ray-tracing models at high electron beta. FW heating at the ~2 MW level to ELMy H-mode discharges in the ITER Baseline Scenario (IBS) showed unexpectedly strong absorption of FW power by injected neutral beam (NB) ions, indicated by significant enhancement of the D-D neutron rate, while the intended absorption on core electrons appeared rather weak. The AI and IBS discharges are compared in an effort to identify the causes of the different response to FWs. [ABSTRACT FROM AUTHOR]

At ASDEX Upgrade the ECRH system has been upgraded to provide up to 4 MW of heating power at 140 GHz (or 2:2 MW at 105 GHz). The power at 140 GHz exceeds the minimum H-mode power threshold for typical high Ip; Bt conditions by approximately a factor of two. The upgrade allows H-modes with dominant electron heating and significant electron-ion heat exchange to be studied, i.e. the situation expected in ITER. This paper reports on systematic studies varying the heating mix with NBI, ICRF and ECRH and its effect on pedestal parameters and core transport. The H-mode pedestal is hardly affected by the choice of heating mix, but the ion temperature in the plasma center is found to vary significantly. The ion channel dominates heat transport and ion temperature gradient modes (ITG) are found to be the most unstable microinstability in all the scenarios considered. R/LTi at half radius reduces by a factor of two when Te/Ti increases from 0.9 to 1.5. TGLF modelling of the electron and ion temperature and electron density profiles shows very good agreement with the experimental data when applying a realistic sawtooth model. [ABSTRACT FROM AUTHOR]

An ICRF system with power up to 6.0 MW and a LHCD system up to 4MW have been applied for heating and current drive experiments on EAST. Intensive lithium wall coating was intensively used to reduce particle recycling and Hydrogen concentration in Deuterium plasma, which is needed for effective ICRF and LHCD power absorption in high density plasmas. Significant progress has been made with ICRF heating and LHW current drive for realizing the H-mode plasma operation in EAST. In 2010, H-mode was generated and sustained by LHCD alone, where lithium coating and gas puffing launcher mouth were applied to improve the LHCD power coupling and penetration into the core plasmas at high density of H-modes. During the last two 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, where electrons are predominantly heated by collisions with high energy minority ions. The H-MH mode gave the best plasma performance, and realized H-mode alone in 2012. Combination of ICRF and LHW power injection generated the H-mode plasmas with various ELMy characteristics. The first successful application of the ICRF Heating in the D (He3) plasma was also achieved. The progress on ICRF heating, LHCD experiments and their application in achieving H-mode operation from last two years will be discussed in this report. [ABSTRACT FROM AUTHOR]