Nan Shi

ELMy H-mode confinement and threshold power by low hybrid wave on the EAST tokamak

Stationary type-III ELMy H-mode plasmas were achieved on Experimental Advanced Superconducting Tokamak (EAST) by low hybrid wave in 2010. The threshold power increases with plasma density, and a significant reduction in the H-mode occurs by decreasing the distance between the X-point and the strike point at the outside lower divertor on EAST. A series of statistics for the H-mode confinement such as the dependence of energy confinement time (τE) on plasma density and loss power is experimentally studied in detail.

Extension of operational limits on EAST

The first plasma has been achieved successfully in the Experimental Advanced Superconducting Tokamak (EAST). Boronization by the glow discharge (GDC) method was studied in experiments. The plasma performance was obviously improved by GDC boronization. Extension of the operational region and improvement in the plasma performance were obtained. Sawtooth discharges were observed by means of soft x-ray signals, electron cyclotron emission signals and line averaged electron density after boronization. Lower qa and more stable operation were also achieved following GDC boronization. The plasma current ramp-up rate was also improved as a result of decreased impurity content and low averaged loop voltage due to boronization. PLEASE NOTE: THERE HAS BEEN A RETRACTION PUBLISHED FOR THIS ARTICLE.

Study of laser output power stabilization for a deuterium cyanide laser interferometer on the Experimental Advanced Superconducting Tokamak

A control system which can improve stabilization of laser power in long-term operation automatically is designed for a deuterium cyanide (DCN) far-infrared laser interferometer on the Experimental Advanced Superconducting Tokamak. It stabilizes the output power of the laser by a closed-loop control system aided by a programmable logic controller. The system has been applied to the DCN laser and it has been proven that it is effective in stabilizing the laser near the highest scope of the output power.

Design of Remote Control System for Far-Infrared Laser Interferometer

A remote control system is designed to achieve the stable and economical operation of far-infrared laser interferometer on the EAST Machine (Experimental Advanced Superconducting Tokamak). Based on the PLC controller, the system is set up as two parts: gas flow control for adjusting working gas, feedback control for stabilizing output power of the laser. We demonstrate the feasibility that, according to the need of experiment, the working gas ratio mode can be changed in order to save gas (CD4 ) instead of keeping a single-mode ratio. Meanwhile, the changes of the output power and power supply of the laser have been measured due to the mode conversion. The output power of the DCN laser, as a laser source, is influenced by a number of parameters, especially the gas ratio and a variety of disturbances. Therefore, the feedback control system has been developed to make the laser power stable near the maximum available power. The whole system has been applied to the DCN laser, and has been proved to be effective.Copyright

Study of a DCN laser interferometer/polarimeter for EAST tokamak

The experimental advanced superconducting tokamak (EAST) is a non-circular advanced steady-state experimental device. The first plasma discharge has been achieved successfully on the EAST in 2006. Single-null (SN) and double-null (DN) diverter plasmas discharges have also been achieved successfully on the EAST Tokamak in 2007. A five-channel vertical DCN laser interferometer/polarimeter system will be constructed on the EAST device. The system will be used mainly for getting electron density profile and poloidal current profile, and for a density feedback control simultaneously. Three 195 mu m(1.54 THz) continuous-wave glow discharge deuterium cyanide(DCN) lasers are implemented as beam sources. The system employs a three-wavelength configuration that simultaneously produces interferometric phase shift and Faraday rotation polarimetric data from a single detector for each channel. The optical system including optics inside the completely sealed frame has been designed in the consideration of long beam paths in a narrow diagnostics port and avoiding loss of laser power when laser passes through the moist atmosphere. By the same token, high sensitivity THz InSb detector system will be used in this interferometer/polarimeter system.