First results of LHCD experiments with 4.6 GHz system toward steady-state plasma in EAST

Abstract

A 4.6 GHz lower-hybrid current drive (LHCD) system has been firstly commissioned in EAST in the 2014 campaign. The first LHCD results with 4.6 GHz show that LHW can be coupled to plasma with a low reflection coefficient, drive plasma current and plasma rotation, modify the plasma current profile, and heat plasma effectively. By means of configuration optimization and local gas puffing near the LHW antenna, good LHW-plasma coupling with a reflection coefficient less than 5% is obtained. The maximum LHW power coupled to plasma is up to 3.5 MW. The current drive (CD) efficiency is up to 1.1 × 10 19 A m −2 W −1 and the central electron temperature is above 4 keV, suggesting that LH power could be mainly deposited in the core region, which is in agreement with code simulation. Experiments show that the current profile is effectively modified and toroidal rotation in the co-current direction is driven by the LHCD. Also, the CD efficiency and current profile depend on the launched wave spectrum, suggesting the possibility of controlling the current profile by changing the phase difference. Repeatable H-mode plasma is obtained by either the 4.6 GHz LHCD system alone, or together with a 2.45 GHz LHCD system, the NBI (neutral beam injection) system. The different ELM features of H-mode between the different heating methods are under investigation.

Experimental observation of reverse-sheared Alfvén eigenmodes (RSAEs) in ELMy H-mode plasma on the EAST tokamak

“…The analyzed plasmas are for developing long pulse high β N operation [29]. The auxiliary heating method in these plasmas is lower hybrid wave (LHW) at 4.6 GHz [30] and neutral beam injection (NBI) [31]. The NBI system is composed of two beam lines.…”

Development and Application of 3.7GHz LHCD system on HL-2A and Development of RF Heating system on HL-2M

“…A dedicated gas puffing system with three poloidal injection points is installed next to the launcher mouth, on the left of the launcher, signed by the arrows in Fig 2. Local gas puffing near LH launchers has been used routinely, for example in JET [9] and EAST [10], as a method to increase the local density and improve the LH coupling, in particular during H-mode operation. A set of Langmuir probes, consisting of a total of eight probes mounted at two radial locations, is installed on the right hand side of the launcher mouth.…”

Lower hybrid current drive experiments in support of high confinement long pulse operation in EAST

“…The 2.45 GHz launcher has 20 modules of eight waveguides, mounted in five rows and four columns [5]. The 4.6 GHz launcher is composed of 24 modules of 3×24 waveguides, mounted in four rows and six columns [6]. The launched wave spectra for different phasing between modules for the 4.6 GHz launcher are shown in Figure 1.…”

“…The unique Lower Hybrid Current Drive (LHCD) capability, i.e. two LHCD systems at different frequencies (2.45 GHz [5] and 4.6 GHz [6]), has allowed comparing the CD efficiency of the two LHCD systems [7]. Extensive modelling with the ray-tracing + Fokker-Planck codes C3PO/LUKE [8] has been performed in support to the experiments [3].…”