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Recent studies have shown that helicon waves may be an attractive option for driving an efficient off-axis current drive in order to supplement bootstrap current for steady state operation in fusion reactors. Based on the China fusion engineering test reactor parameters, the helicon wave trajectories, profiles of driven current and current driven efficiency are calculated with the ray-tracing code GENRAY. Both the peak position and the peak value of driven current profiles are dependent on the wave frequency. In the frequency range of 1.6 GHz–2.0 GHz, the peak value increases with the increase of frequency, and the peak position has a slight change (concentrate around ρ= 0.75). High electron temperature and low electron density seem to be favorable for the helicon wave absorption. A driving current of I/P > 70 kA MW−1 at the off-axis position of ρ < 0.7 can be obtained with the electron temperature at the plasma center, T e(0) < 25.4 keV and the electron density at the plasma center, n e(0) ∼ 0.7 × 7.8 × 1019m−3–0.8 × 7.8 × 1019m−3. The current drive efficiency decreases with the increase of the electron density. Peak positon of the driven current profile is insensitive to the parallel refractive index n ∥. It is found that the poloidal launch angle has some effect on the peak positon and its value. [ABSTRACT FROM AUTHOR]

It is critical to keep a low level of tungsten impurity concentration in the core plasma of the fusion reactor. Using the OEDGE code, the influence on the tungsten concentration due to the cross-field transport in the scrape-off layer is studied. Based on the design parameters of the China Fusion Engineering Test Reactor, the background plasma with the peak target electron temperature of 15 eV is generated using the onion-skin model. The neon impurity with the assumed concentration of 0.2% inside the separatrix is included for estimating the tungsten sputtering source. In a series of simulations of tungsten transport, the diffusion coefficient D⊥ is varied from 0.1 to 10 m2 s−1, and the hypothetical inward pinch velocity VIMP is in the range of 0–5 m s−1. The tungsten concentration inside the separatrix increases with decreasing diffusion coefficient and exceeds 10−5 for the diffusion coefficient lower than about 0.2 m2 s−1. When the hypothetical inward pinch is included, the tungsten concentration increases. The relation between the relative increase in tungsten concentration and VIMP/D⊥ is fitted. [ABSTRACT FROM AUTHOR]

The dominant two-fluid magnetohydrodynamic (MHD) stabilities of China Fusion Engineering Test Reactor upgrade phase-I baseline equilibria in presence of perfect conducting wall have been evaluated using the initial value code NIMROD. Our MHD simulations show that for equilibrium with qaxis < 1, high-n edge localized modes are slightly stabilized by toroidal shear flow, and n = 1 mode is found to be unstable in the core region with the characteristic of sawtooth instability. For qaxis > 2 equilibrium, all modes are found to be unstable but edge localized both in single-fluid and two-fluid MHD models. Specifically for n ≤ 13 modes, the two-fluid MHD model gives a slightly higher growth rate than the single-fluid MHD model, while for n > 13 modes, this trend becomes the opposite, which means the two-fluid MHD model is needed for high-n mode analysis. In addition, n = 1–10 modes are found to be more unstable with increasing wall position and eventually their growth rates approach values in the no-wall limit. [ABSTRACT FROM AUTHOR]

The Keda Torus eXperiment (KTX) is a medium-sized reversed field pinch (RFP) device under construction at the University of Science and Technology of China. The KTX has a major radius of 1.4 m and a minor radius of 0.4 m with an Ohmic discharge current up to 1 MA. The expected electron density and temperature are, respectively, 2 × 1019 m−3 and 800 eV. A combination of a stainless steel vacuum chamber and a thin copper shell (with a penetration time of 20 ms) surrounding the plasma provides an opportunity for studying resistive wall mode instabilities. The unique double-C design of the KTX vacuum vessel allows access to the interior of the KTX for easy first-wall modifications and investigations of power and particle handling, a largely unexplored territory in RFP research leading to demonstration of the fusion potential of the RFP concept. An active feedback mode control system is designed and will be implemented in the second phase of the KTX program. The recent progress of this program will be presented, including the design of the vacuum vessel, magnet systems and power supplies. [ABSTRACT FROM AUTHOR]