Xiao Bingjia

Equilibrium Reconstruction in EAST Tokamak

Reconstruction of experimental axisymmetric equilibria is an important part of tokamak data analysis. Fourier expansion is applied to reconstruct the vessel current distribution in EFIT code. Benchmarking and testing calculations are performed to evaluate and validate this algorithm. Two cases for circular and non-circular plasma discharges are presented. Fourier expansion used to fit the eddy current is a robust method and the real time EFIT can be introduced to the plasma control system in the coming campaign.

WebScope: A New Tool for Fusion Data Analysis and Visualization

A visualization tool was developed through a web browser based on Java applets embedded into HTML pages, in order to provide a world access to the EAST experimental data. It can display data from various trees in different servers in a single panel. With WebScope, it is easier to make a comparison between different data sources and perform a simple calculation over different data sources.

Online Plasma Shape Reconstruction for EAST Tokamak

An online plasma shape reconstruction, based on the offline version of the EFIT code and MPI library, can be carried out between two adjacent shots in EAST. It combines online data acquisition, parallel calculation, and data storage together. The program on the master node of the cluster detects the termination of the discharge promptly, reads diagnostic data from the EAST mdsplus server on the completion of data storing, and writes the results onto the EFIT mdsplus server after the calculation is finished. These processes run automatically on a nine-nodes IBM blade center. The total time elapsed is about 1 second to several minutes, depending on the duration of the shot. With the results stored in the mdsplus server, it is convenient for operators and physicists to analyze the behavior of plasma using visualization tools.

Capability Assessment of the Equilibrium Field System in KTX

Radial equilibrium of the KTX plasma column is maintained by the vertical field which is produced by the equilibrium field coils. The equilibrium is also affected by the eddy current, which is generated by the coupling of copper shell, plasma and poloidal field coils. An equivalent circuit model is developed to analyze the dynamic performance of equilibrium field coils, without auxiliary power input to equilibrium field coils and passive conductors. Considering the coupling of poloidal field coils, copper shell and plasma, the evolution of spatial distribution of the eddy current density on the copper shell is estimated by finite element to analyze the effect of shell to balance. The simulation results show that the copper shell and equilibrium field coils can provide enough vertical field to balance 1 MA plasma current in phase 1 of a KTX discharge. Auxiliary power supply on the EQ coils is necessary to control the horizontal displacement of KTX due to the finite resistance effect of the shell.

Characterization of plasma current quench during disruption in EAST tokamak

A preliminary analysis of plasma current quenching is presented in this paper based on the disruption database. It demonstrates that 26.8% of discharges have been disrupted in the last 2012 campaign, in addition, the plasma disruptive rate grows with the increase of plasma current. The best-fit linear and instantaneous plasma current quench rate is extracted from the recent EAST disruptions, showing that an 80%–30% interval of the maximum plasma current is well fit for the EAST device. The lowest area-normalized current quench time is 3.33 ms/m2 with the estimated plasma electron temperature being 7.3 eV,~9.5 eV. In the disruption case the maximum eddy current goes up to 400 kA, and a fraction of currents are respectively driven on the upper and lower outer plate with nearly 100 MPa–200 MPa stress in the leg.

Performance Enhancements in the EAST Digital Plasma Control System

The EAST plasma control system (PCS) is in continuous development to satisfy the EAST experimental requirements. In order to realize low latency and distortion-free signal transmission between PCS and servo systems such as the poloidal field power supply, in-vessel coil power supply and real-time scope, reflective memory boards (RFM) were applied. The new hardware layout and enhanced performance are reported. Newly implemented PCS control algorithms for gas control and real-time data display are also presented.

Construction and Implementation of the Online Data Analysis System on EAST

In order to obtain diagnostic data with physical meaning, the acquired raw data must be processed through a series of physical formulas or processing algorithms. Some diagnostic data are acquired and processed by the diagnostic systems themselves. The data processing programs are specific and usually run manually, and the processed results of the analytical data are stored in their local disk, which is unshared and unsafe. Thus, it is necessary to integrate all the specific process programs and build an automatic and unified data analysis system with shareable data storage. This paper introduces the design and implementation of the online analysis system. Based on the MDSplus event mechanism, this system deploys synchronous operations for different processing programs. According to the computational complexity and real-time requirements, combined with the programmability of parallel algorithms and hardware costs, the OpenMP parallel processing technology is applied to the EAST analysis system, and significantly enhances the processing efficiency.

Web-based Logbook System for EAST Experiments

Implementation of a web-based logbook system on EAST is introduced, which can store the comments for the experiments into a database and access the documents via various web browsers. The three-tier software architecture and asynchronous access technology are adopted to improve the system effectively. Authorized users can view the information of real-time discharge, comments from others and signal plots; add, delete, or revise their own comments; search signal data or comments under complicated search conditions; and collect relevant information and output it to an excel file. The web pages can be automatically updated after a new discharge is completed and without refreshment.

A Flexible Visualization Tool for Rapid Access to EFIT Results

This paper introduces the design and implementation of an interactive tool, the EASTViewer, for the visualization of plasma equilibrium reconstruction results for EAST (the Experimental Advanced Superconducting Tokamak). Aimed at the operating system independently, Python, when combined with the PyGTK toolkit, is used as the programming language. Using modular design, the EASTViewer provides a unified interface with great flexibility. It is easy to access numerous data sources either from local data files or an MDSplus tree, and with the pre-defined configuration files, it can be extended to other tokamaks. The EASTViewer has been used as the major tool to visualize equilibrium data since the second EAST campaign in 2008, and it has been verified that the EASTViewer features a user-friendly interface, and has easy access to numerous data sources and cross-platforms.

Implementation of Gas Control Algorithm in EASTPCS

In this paper, gas control on EAST in open and closed loop is discussed and its implementation into EASTPCS (plasma control system for the experimental advanced superconducting tokamak) is introduced. Using a model to describe the plasma density response to the gas puff command, a gas simulation server (simserver) using MATLAB® simulink tools and real time workshop was built up. Proper operation of the gas control algorithm was verified using this simserver. The simulation results suggested that the gas control can be applied in the next EAST campaign.