KTX反场箍缩装置纵场线圈结构设计与电磁分析

KTX反场箍缩装置的主要参数介于RFX装置与MST装置之间。反场箍缩的外加纵场需跟随等离子体电流的演化而变化,同时由于RFP中的磁面对于外部特别是等离子体边界处的径向磁场较敏感,所以需外部线圈的磁场更加精细,这对于线圈的磁场分布、误差场以及波纹度等的设计提出了更高的要求。根据KTX物理目标参数要求,提出矩形和楔形截面纵场磁体线圈设计方案,借助有限元软件和程序分析了其电磁场空间分布和结构受力大小。结果表明,6.4°楔形截面方案相比矩形截面方案在控制误差场方面更具有可行性。     

Design of a Wedge-Shaped Toroidal Field Winding for KTX Device

The KTX device is a reversed field pinch(RFP)device currently under construction.Its maximum plasma current is designed as 1 MA with a discharge time longer than 100 ms.Its major radius is 1.4 m and its minor radius is 0.55 m.One of the most important problems in the magnet system design is how to reduce the TF magnetic field ripple and error field.A new wedgeshaped TF coil is put forward for the KTX device and its electromagnetic properties are compared with those of rectangular-shaped TF coils.The error field Bn/Btof wedge-shaped TF coils with6.4 degrees is about 6%as compared with 8%in the case of a rectangular-shaped TF coil.Besides,the wedge-shaped TF coils have a lower magnetic field ripple at the edge of the plasma region,which is smaller than 7.5%at R=1.83 m and 2%at R=1.07 m.This means that the tokamak operation mode may be feasible for this device when the plasma area becomes smaller,because the maximum ripple in the plasma area of the tokamak model is always required to be smaller than 0.4%.Detailed analysis of the results shows that the structure of the wedged-shape TF coil is reliable.It can serve as a reference for TF coil design of small aspect ratio RFPs or similar torus devices.     

The residual zonal flow in tokamak plasmas with a poloidal electric field

In a tokamak plasma with auxiliary heating by cyclotron waves, a poloidal electric field will be produced, and as a consequence influence the residual zonal flow(RZF) level. The poloidal electric field can also be induced through biasing electrodes at the edge region of tokamaks.Numerical evaluation for a large aspect ratio circular cross section tokamak for the electron cyclotron wave heating indicates that the RZF level decreases significantly when the poloidal electric field increases. Qualitatively, the ion cyclotron wave heating is able to increase the RZF level. It is difficult to apply the calculation to the real cyclotron wave heating experiments since we need to know factors such as the plasma profiles, the exact power deposition and the cross section geometry, etc. It is possible to use the cyclotron wave heating to control the zonal flow and then to control the turbulence level in tokamak experiments.     

KTX反场箍缩装置主支撑结构设计与分析

KTX反场箍缩实验装置主支撑由柔性支撑和支撑平台组成,主要用来支撑真空室、导体壳和纵场线圈的重量。鉴于主支撑结构的重要性,通过有限元分析和理论分析相结合的方法对主支撑进行了强度分析和稳定性分析,给出了主支撑应力分布和变形情况及不同结构参数下的临界载荷。分析结果验证了主支撑结构的可行性,并为主支撑的后续优化设计提供理论依据。     

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.     

Numerical analysis of MD events and preliminary thermal calculation for KTX vacuum vessel

KTX is a new reversed field pinch (RFP) magnetic confinement device which is under design in ASIPP and USTC. Major disruption (MD) events may occur in future operating process, which is simulated with the finite element (FE) method. The results present that the peaks of eddy currents on vessel and conductor shell are respectively 11.791 kA and 68.637 kA with maximum stress 67.1 MPa due to high transient electromagnetic (EM) force. It is confirmed that the structure is still strong enough to bear the electromagnetic loads even if the worst case. Besides, as KTX vacuum vessel will take the method of natural cooling for heat dissipation during plasma discharge (0.5–1.0 MA), a preliminary thermal calculation was implemented in normal condition to decide suitable time parameters such as duration and interval. It is suggested that the discharge interval should be no less than 5 min for the complete 1 MA plasma with 100 ms duration, which can guarantee the temperature of vacuum vessel below 200 °C.     

A poloidal field control system based on VxWorks in HT-7 Tokamak

The PF (Poloidal Field) control system is one of the most important control systems in HT-7 Tokamak.Most of parameters such as plasma current, plasma horizontal position and plasma vertical position will be monitored.For the purpose of long-pulse discharge and the more precise control to plasma, the real-time operation system VxWorks is applied, instead of the behindhand and unbefitting DOS operation system. This paper describes the development process of HT-7 PF control system based on VxWorks on Intel X86 platforms. The method of using hardware cards in VxWorks, and the network communication with other operation systems are discussed especially. Results of the comparison between VxWorks and DOS operation systems are given too.     

基于DSP的HT-7极向场多变量控制处理

为提高实时性,根据HT-7极向场多变量控制器的工作原理,以DSP技术为主,设计控制器的硬件结构.在研制用于核心数据处理的DSP卡中,注意有效结合DSP芯片TMS320VC33与其他芯片的技术特性,如采用双口RAM实现数据传输与处理的并行,利用DSP仿真器实现程序的固化等,使其各项功能满足控制处理要求.在发挥硬件特性的基础上,合理优化了控制过程与处理算法,如采用DMA传输技术、定时器中断等保证控制处理的实时性,进行了软件开发.     

Design and Analysis of the Poloidal Field Grid Power Supply System for the HT-7 Tokamak

This paper reports a new project - the poloidal field （PF） grid power supply system to replace the ac flywheel generator power supply system on the basis of the present running parameters of the HT-7 poloidal field and the short-circuit capacity of our transformer substation. The designed parameters of the PF grid power supply system have been verified to meet the requirements of the heating field （HF） and the vertical field （VF）. In the meantime, in order to reduce the disturbance to the local power grid, the device of reactive power and harmonic current compensation has been added. Experimental results have confirmed the feasibility of the PF grid power supply system. Compared with the ac flywheel generator, the PF grid power supply system has the advantages of lower noise, precise control, convenient maintenance, simple operation and cost savings.     

直动电磁阀磁场特性分析

控制棒水压驱动技术是清华大学核能与新能源技术研究院具有自主知识产权的一项新型发明专利技术.组合阀属于该项技术的关键部件,组合阀是由三个直动电磁阀组成,电磁阀的性能直接影响组合阀的性能,从而影响控制棒水压驱动技术的运行性能.本文就控制棒水压驱动系统运行过程中所出现的异常工况,运用ANSYS电磁场分析软件,对其直动电磁阀的多种运行工况进行了电磁场特性分析.分析结果表明:导磁材料的不当使用形成磁路的改变,引起某些工况下磁力反向,使电磁阀在特定情况下出现故障,进而造成控制棒水压驱动系统异常;通过电磁场特性分析可以进一步优化直动电磁阀的设计.     

脉冲强磁场探测系统的基本实现

简要介绍了电磁感应法测量脉冲强磁场的原理,并对基于此原理的探测系统进行了实现,最后对实验结果予以分析,给出了主要误差来源.     

Preliminary Design of GDC System for KTX Device

KeDa Torus for eXperiment (KTX) is a reversed field pinch magnetic confinement fusion research device whose main parameters are between in the RFX and MST. The base vacuum of KTX is 1 × 10^?6 Pa. Six sets of turbomolecular pumps parallel installed in the six horizontal ports which served as the main pumping system for KTX and the diameters of the ports are 0.15 m. Before plasma discharge, glow discharge cleaning (GDC) system is applied to clean C, O and hydrocarbon impurity on the vacuum vessel (VV) surfaces of KTX. An inflation system and residual gas analyzer system are designed to supply the working gas and monitoring the effect of GDC respectively. According to the GDC experiment practice, the working gas pressure of the KTX GDC system is designed as 0.3 Pa, with average current density of 0.15 A/m². Two sets of the GDC probes are installed in KTX horizontal ports symmetrically with interval angle of 180º and the input current of each anode is 1.6 A. According to the current density distribution, the centre of the VV cross section is the superior working area for GDC anode, a screw-nut pairs with the cooperation of bellows can transfer the anode from its storage position to its working position, and the stroke of the screw-nut pairs is 0.5 m. Based on the temperature rise calculation, the maximum equilibrium temperature of the anode during glow discharge is about 275 °C (under 200 °C baking). The thermal stresses caused by the temperature distribution on the anode’s components especially in the vacuum brazing areas are inspected during GDC process. All the simulation results show that the structure and base material of the KTX GDC anode can work normally without additional active cooling system.     

用边界元法计算加速器元件的电磁场

本文试图采用基于边界积分方程的一种边界分元的数值计算方法——边界元法,来分析我所2×6MV串列加速器的束流光学元件的电磁场。因为该方法不同于有限差分法和有限单元法的新方法,而且它具有以下优点:边界无法所依据的数学原理简单、易懂,便于推广应用;数值计算精度高;目前广泛应用的有限单元法和有限差分法都属于‘域法’,即在整个求解域里划分成许多细小的单元或网格,然后把各单元或网格换成简单的等价模型,再把它们联系起来。而边界元法只需要在边界上剖分、离散。因此,解算一个问题所要的方程组少,输入数据简单等。     

On the Sequential Control of ITER Poloidal Field Converters for Reactive Power Reduction

Sequential control applied to the International Thermonuclear Experimental Re- actor （ITER） poloidal field converter system for the purpose of reactive power reduction is the subject of this investigation. Due to the inherent characteristics of thyristor-based phase-controlled converter, the poloidal field converter system consumes a huge amount of reactive power from the grid, which subsequently results in a voltage drop at the 66 kV busbar if no measure is taken. The installation of a static var compensator rated for 750 MVar at the 66 kV busbax is an essential way to compensate reactive power to the grid, which is the most effective measure to solve the problem. However, sequential control of the multi-series converters provides an additional method to improve the natural power factor and thus alleviate the pressure of reactive power demand of the converter system without any additional cost. In the present paper, by comparing with the symmetrical control technique, the advantage of sequential control in reactive power consumption is highlighted. Simulation results based on SIMULINK are found in agreement with the theoretical analysis.     

The Design of the Plasma Control System in KTX

KTX(Keda Torus for eXperiment)is a new reversed field pinch device.The KTX plasma control system(PCS)can provide real-time,stable,flexible plasma control which is designed by ASIPP(Institute of Plasma Physics,Chinese Academy of Sciences),based on the Linux cluster system and EPICS(Experimental Physics and Industrial Control System)framework,and developed from DIII-D(Doublet III-D)PCS.The control of the equilibrium field in KTX uses a PID(Proportional-Integral-Derivative)feedback controller.The control of the gas injection is an open loop control.The plasma control simulation system is one part of the plasma control system,which is used to test the plasma control algorithm if it is revised and updated.The KTX PCS has been successfully tested using HT-7(Hefei Torus 7)experiment data in simulation mode.In the next phase,an error field feedback control and KTX simulator will be added to the KTX PCS,and the KTX PCS will be applied in experiments in the future.     

Discovering exact,gauge-invariant,local energy-momentum conservation laws for the electromagnetic gyrokinetic system by high-order field theory on heterogeneous manifolds

Gyrokinetic theory is arguably the most important tool for numerical studies of trarnsport physics in magnetized plasmas.However,exact local energy-momentum conservation laws for the electromagnetic gyrokinetic system have not been found despite continuous effort.Without such local conservation laws,energy and momentum can be instantaneously transported across spacetime,which is unphysical and casts doubt on the validity of numerical simulations based on the gyrokinetic theory.The standard Noether procedure for deriving conservation laws from corresponding symmetries does not apply to gyrokinetic systems because the gyrocenters and electromagnetic field reside on different manifolds.To overcome this difficulty,we develop a high-order field theory on heterogeneous manifolds for classical particle-field systems and apply it to derive exact,local conservation laws,in particular the energy-momentum conservation laws,for the electromagnetic gyrokinetic system.A weak Euler-Lagrange (EL) equation is established to replace the standard EL equation for the particles.It is discovered that an induced weak EL current enters the local conservation laws,and it is the new physics captured by the high-order field theory on heterogeneous manifolds.A recently developed gauge-symmetrization method for high-order electromagnetic field theories using the electromagnetic displacement-potential tensor is applied to render the derived energy-momentum conservation laws electromagnetic gauge-invariant.     

A web application for poloidal field analysis on HL-2M

Recently, many web tools [1], [2], [3] in fusion society have been designed and demonstrated, which has been proved to be powerful and convenient to fusion researchers. Many physicists and engineers need a tool to compute the poloidal magnetic field for some purposes (for example, the calibration of magnetic probes for EFIT, the field null structure analysis for control, the design of some plasma diagnostic systems), so to develop a powerful and convenient web application for the calculation of magnetic field and magnetic flux produced by PF coils is very important. In this paper, a web application tool for poloidal field analysis on HL-2M with a totally original framework is presented. This web application is full of dynamic and interactive interface, and can run in any popular browser (IE, safari, firefox, opera), on any hardware (smart phone, PC, ipad, Mac) and operating system (ios, android, windows, linux, Mac OS). No any plugins is needed. The three layers (jQuery + PHP + Matlab) of this framework are introduced. The front top client layer is developed by jQuery code. The middle layer, which plays a role of a bridge to connect the server and client through socket communication, is developed by PHP code. The behind server layer is developed by Matlab, which compute the magnetic field or magnetic flux through a Special Function called Complete Elliptic Integral, and returns the results in the client favorite way, either by table or by JPG image. The field null structure and the vertical and radial field structure calculated by this tool are introduced with details. The idea to design a web tool with jQuery + PHP + Matlab framework may apply to other machines. The address for this application is http://dp.swip.ac.cn/hl2m.     

On the Physics of Improved Confinement During Pulsed Poloidal Current Drive in MST Reversed-Field Pinch

Reduction of core-resonant magnetic fluctuations and improved confinement in the Madison Symmetric Torus reversed-field pinch (MST RFP) have been routinely achieved by applying the surface poloidal electric field. The created inductive poloidal electric field drives current in plasma which leads to the improved confinement. To study the effect we developed a relatively simple 1-D model in cylindrical geometry which assumes poloidal and axial symmetry during the drive. We use resistive magnetohydrodynamics model with realistic plasma parameters and assume that there is a vacuum gap between plasma boundary and conducting wall of the vessel. Evolution of plasma density is taken into account and plasma boundary moves self-consistently with momentum equation. We start from an initial unstable equilibrium and examine stability of plasma configuration at intermediate moments of time during the drive. For this we calculate the growth rates of unstable eigenmodes in the plasma. Our results show that the modifications to the plasma current profile during the drive are stabilizing. The initial stabilization is due to the direct modification of the current profile near the edge. It enhances later in time due to the flattening of λ profile in the core region as plasma and magnetic field compress inward during the drive.     

ITER用极向场线圈导体短样分流温度测试

ITER用极向场（PF）线圈CICC导体短样是用西部超导材料科技有限公司提供的NbTi超导股线绕制完成,该股线在不同温度下的临界电流测试性能稳定,符合绕制导体的要求。对PF导体短样在SULTAN实验室进行了测试,经电磁循环通电前后,分流温度无较大改变,导体性能稳定。在考虑了导体自场作用的情况下,导体在5T、50kA运行环境下的分流温度为6.33K,满足ITER规定的要求。     

60Co集装箱CT检测系统检查流程控制设计

简要介绍了60Co集装箱CT检测系统的原理,详细分析了控制子系统的功能,并进行了三种自动扫描模式的检查流程控制设计.系统的实际运行结果表明,检查流程控制设计合理、高效.