Magnetic Fluctuation Measurement And Analysis On SUNIST

SUNIST, built as the first Spherical Tokamak in China, focus mainly on advancing our understanding of the magnetic confinement plasma physics at a low aspect ratio (R/a down to 1.3) and demonstrating the possibility of the stable plasma setup by non-inductive startup. The main task of this article is concentrating on magnetic fluctuations measurement, making use of the magnetic field measurement system, and the subsequent analysis of the relationship between magnetic fluctuations and the anomalous transport. It is well-known that fluctuations in the magnetic field are a potent mechanism for the anomalous transport of energy in confined plasmas. A lot of correlative research has been taken in the reversed field pinch and the traditional tokamak and indicated that there is a close relationship between magnetic fluctuations and edge transport. Unfortunately, limited by the feasible positions of coils, all previous research concentrated on the edge plasmas, which is obviously not direct enough to reflect the propagating situation of turbulence from the core to the SOL. Our work is to investigate the relationship between magnetic fluctuations and anomalous transport in Spherical tokamaks (STs) from the core to the limiter. Concretely, we take the research with the magnetic field measurement system and give the radial profiles of magnetic fluctuations, which indicate that the magnetic-fluctuation-driven transports cannot be ignored compared with the electrostatic-fluctuation-driven ones. Then we use the standard two-point-cross-correlation technique to estimate wavenumber spectrum and give the phase velocity of turbulence, which indicates that the turbulence transports radially both in the outward and inward direction, and the superposition effect makes the turbulence transport from the core to the SOL. Besides, both the radical profiles of phase velocity and that of correlation coefficient indicate that the SOL has a certain effect on anomalous transports.