Experimental Investigations On The Transport In A Steady-state Toroidal Plasmas

In this work,we investigate the properties of the blobs and the large-scale poloidal spin in KT-5D steady-state toroidal plasmas,with the goal of exploring new representations for statistical and spatiotemporal data and of identifying specific control parameters for turbulence.The work is performed in the double functional toms of KT-5D in the University of Science and Technology of China.Using the specified 57-pin Langmuir probe arrays with the best spatial resolutions of 2cm×2cm so far to diagnose the plasma parameters of the whole cross section,we caught two-dimensional evolutions of blobs for the first time in the KT-5D steady-state toroidal plasmas.It shows that blobs form from the density peak of the central plasmas,and propagate radially,resulting in important energy and particle losses.The lifetime of blobs is at the order of 100μs, and the typical velocity is about 10~3 m/s.The radially elongated density structure can be sheared by the E×B flow,which is responsible for the convection between the high field side plasmas and the low field side plasmas.More than half of the total particle loss is induced by the blobs,implying that blobs constitute the dominant loss channel.Fast camera is also used to take the pictures of the blobs,affirming the credibility of the results from probe data.This work also presents the findings of large-scale poloidal spin in KT-5D steady-state plasmas.The spatial scale of the spin is over square centimeter.It occurs at the low field side,with an average velocity of 10~3 m/s.The existence of spin maybe unpuzzles the kHz-order peak in the power spectra of the ion saturation current in different tokamaks and steady-state toroidal devices.One-dimensional continuous wavelet analysis is used here to investigate the temporal properties of the blobs and the large-scale poloidal spin,finding that the blob is temporally intermittent,while the large-scale poloidal spin is periodic.The correlations between the blob,the large-scale poloidal spin and the magnetic shear is carefully discussed.Statistical analyses clearly show that the shear induced by the vertical magnet field can weaken large-scale poloidal spin.The transport caused by the blobs will be significantly restrained by means of adding a properly vertical magnet field,or,in other words,increasing the magnetic shear.The relationship between the key plasma parameters and the vertical magnetic field is also presented.It is not a bigger,but an optimum vertical magnetic field brings on a highest plasma density and electron temperature.The relative magnitude of the radial particle loss and the parallel particle loss is determined by the ratio of the vertical magnetic field to the toroidal magnetic field.Author's work on new hardware is also presented here,together with some experimental results.These include:1) power source system of the toroidal magnetic field for steady-state discharge;2) time-oriented sequential control system for steady-state discharge;3) vertical microwave injection system;4) two-dimensional 57-pin Langmuir probe arrays;5) low-noise broadband differential optoisolator for Langmuir probes;6) software for fast camera system.