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The control system for poloidal field (PF) in ITER is running in a cluster of distributed controller nodes connected by a soft real-time network. The non-functional performance of network communication, such as latency and jitter, plays an important role in the control system. We analyze the essential of network communication for PF converter control system with stringent real-time requirement and identify the feasibility of the conventional time division method at the request of current data size. However, in order to meet the increased demand for communication data size, we present the design of a timed-token based method and its network scheduler. A test scenario involving a cluster of local control cubicles has been set up to verify the method. The test result shows the timed-token method is more competent to the conventional method and more qualify to the networked control system of PF converter. Meanwhile, in other network with similar architecture, implementation of the timed-token method can guarantee real-time performance as well.

China International Nuclear Fusion Energy Program Execution Center (ITER China), the China Domestic Agency for ITER, is in charge of about 7.51% of the Toroidal Field (TF) conductors, 65.15% of the Poloidal Field (PF) conductors, namely 11 TF conductors and 60 PF conductors. All those conductors are supplied in-kind by ITER China. Following success in qualification test on full-scale short conductor samples, ITER China is stepping into the series production of the TF and PF super conductors. Several tons of Nb3Sn and NbTi strands were manufactured, tested, and delivered from strands supplier to assembling supplier under the supervision of the ITER China and all the conductor manufacture processes complied with ITER quality assurance requirements. This article reports the progress on TF and PF conductor of ITER China up to December 2012.

The ITER correction coils (CCs) are designed to be arranged toroidally around the machine inside the poloidal field coils and mounted on the toroidal field coils in order to compensate field errors arising from misalignment of the coils and winding deviations from the nominal shape as a result of fabrication tolerances, joints, leads, busbars CCs, and assembly tolerances. China is responsible for manufacturing all the CCs and their conductor. The paper presents the qualification progress and results of ITER CCs and CC conductor, including the test results of CC SULTAN samples, double pancakes winding experiments, CC case welding techniques, and manufacturing experiment of CC helium inlet/outlets.

This paper describes the bypass circuit design applied to International Thermonuclear Experimental Reactor (ITER) poloidal field converter system. In the baseline design, an internal bypass scheme was designed for purposes of quench protection and reactive power reduction by bypass operation. However, due to the potential risks that exist in case of fault protection, internal bypass scheme is abandoned finally and external bypass scheme is proposed to replace the internal bypass design. In this paper, the weakness of internal bypass design has been reviewed and the reliability of external bypass design at different sites is analyzed. Simulations based on SIMULINK are performed to confirm the reasonability and availability of external bypass proposals.

KSTAR has a nonlinear magnetic material, INCOLOY® alloy 908 (Incoloy), in toroidal field and poloidal field (PF) coil systems. The effect of Incoloy on the magnetic configuration for the plasma ini...

The design of poloidal field (PF) coils and correction coils (CCs) for the International Thermonuclear Experimental Reactor (ITER) relies on the use of 45-kA NbTi cable-in-conduit conductors. All PF5 and CC conductors are produced in China. Research and development programs are needed to acquire knowledge on the behavior of such conductors. Since the conductors are new, full-size copper dummy conductors have been produced in advance for testing the cabling parameters, the definition of the automatic tungsten-inert-gas welding of a seamless jacket section, the elaboration of cable insertion, compaction, etc. Then, two short qualification conductor samples (the PF5 and the CC) are manufactured at the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP), Hefei, China, with the NbTi advanced strands produced by the Western Superconducting Technologies Company, Ltd. In this paper, the manufacturing procedures for the two PF5 and CC conductor samples are described in detail.

In a poloidal field (PF) converter module, fuse protection is of great importance to ensure the safety of the thyristors. The fuse is pre-selected in a traditional way and then verified by finite element analysis. A 3D physical model is built by ANSYS software to solve the thermal-electric coupled problem of transient process in case of external fault. The result shows that this method is feasible.

A bridge arm prototype of ITER poloidal field (PF) converter modules has been designed and fabricated. Non-cophase counter parallel connection is chosen as the arm structure of the prototype. Among all factors affecting current sharing, arm structure is the main one. During the design of the arm prototype, a novel method based on inductance matrixes is employed to improve the current sharing of the bridge arm. The test results on the prototype show that the current sharing performance of the arm prototype is much better than relevant design requirement, and that the matrix method is very effective to analyze and solve the current sharing problems of thyristor converters.

In order to obtain enhanced plasma parameters a complete new tokamak HL-2M is now under construction in Southwestern Institute of Physics. To assure the structural safety of the device for the entire operation cycle, one of the most important issues is the lifetime-limiting effects due to the pulsed operation mode. Fatigue is one of the major failure modes to be considered in mechanical design, and pulsed operation imposes stress with significant alternating components on the support structure (SS). Therefore, the reliability of the whole device is strongly affected by the stress and fatigue characteristic of the SS as the interface structure. This article introduces the SS design and details the fatigue life calculation methods based on the different characteristics of the sub-structures. The fatigue life in hazardous areas of the toroidal field coils anti-torque structure (TFCs-ATs) has been determined by non-linear analysis results. And with the stress-time history data of the vacuum vessel & poloidal field coils support structure (VV&PFCs SS), the fatigue analysis of the hot spots has been completed based on rain-flow counting method and linear cumulative damage method. The calculated minimum fatigue life on TFCs-ATs and VV&PFCs SS is 4.743E+05 and 1.805E+06 cycles, respectively. And the calculated fatigue life on sub-structures can meet the required life for HL-2M tokamak: 1.0E+05 cycles.

Current sharing control is used to assure the stability of unbalanced current between two paralleled bridges when International Thermonuclear Experimental Reactor poloidal field converter operates in parallel mode. This paper, based on the equivalent model of current sharing circuitry, describes the dynamic behavior of current sharing control by means of frequency and time domain methods. A control strategy is proposed and simulations are performed to verify the effectiveness of the proposed strategy in current sharing control.

The dynamic behavior of circulating current control of International Thermonuclear Experimental Reactor poloidal field converter is the subject of this investigation. Four quadrants operation with circulating current has proved to be a reasonable way to perform smooth transition at the zero crossover of load current. In this paper, a control method, specially for circulating current control, on the basis of equivalent circuit, is proposed. With simulations it is verified that the circulating current can be controlled in such a way that it never become zero, and load current can change polarity without any discontinuity and dead zone, even if in the case that the total reference voltage of converter changes rapidly.

A snowflake divertor magnetic configuration (Ryutov in Phys Plasmas 14(6):064502, 2007) with the second-order poloidal field null offers a number of possible advantages for tokamak plasma heat and particle exhaust in comparison with the standard poloidal divertor with the first-order null. Results from snowflake divertor experiments are briefly reviewed and future directions for research in this area are outlined.

This paper introduces the preliminary design of the poloidal field alternating-current/direct-current converter for the coil power supply system applied in the ITER project; it includes the descrip...

This paper presents evaluation of applicability of 2D iron core model for highly non-axisymmetric two limb configuration of GOLEM tokamak (former CASTOR). Presented results explain the long-term discrepancy between measured magnitudes of external poloidal field and those calculated by air-core approach on this tokamak. The model has been applied to two poloidal planes at different toroidal angles in the vacuum vessel region and has shown that close to central column of the transformer, it is possible to correct for 3D effects by variation of chosen dimensions of axisymmetric iron core model. Satisfactory agreement of the 2D model results with the measured distribution of BR field component was achieved.

Wall-conditioning plasmas by ECRF heating (ECWC plasmas) were investigated in KSTAR’s experimental campaigns of 2010 and 2011. Pulses of 110 GHz ECH with an RF power of 200–300 kW were injected into the vacuum vessel, which was filled with helium at a gas pressure ∼1 × 10 −3 mbar. In 2010, the second harmonic of ECH was applied and it was found that the ECRF wave normal to the toroidal field was essentially important for producing high-density plasmas and the uniformity of the plasma was significantly changed with an additional poloidal field pattern by B H and B V . In 2011, the fundamental ECH was applied with additional B H = 0.02 T . The ECWC plasma extended radially toward both the high toroidal field side and low field side. The post-disruption first wall was successfully recovered by 20 pulses of the ECWC plasmas, equivalent to ECWC for 7 min.

This paper presents the commutating over-voltage snubber circuit design method of a thyristor converter that is applied to the International Thermonuclear Experimental Reactor poloidal field-converter module. In the course of poloidal field ac/dc converter normal operation, large transient surges called commutating over-voltages may be generated internally during the commutating process of thyristor, which poses a severe threat to system reliability and needs to be suppressed. In this paper, based on the analysis of reverse recovery transient of the parallel thyristors, the turn-off model of the PF converter thyristor is created and analytical expressions are derived, including the over-voltage crest value and the maximum over-voltage rise rate. Utilizing the analysis results, a systematic approach to the RC snubber circuit design is described.

The ITER superconducting magnet system consists of 18 Toroidal Field (TF) coils, 1 Central Solenoid (CS), 6 Poloidal Field (PF) coils and 18 Correction coils (CC). The TF conductors will be manufactured by China (7%), EU (20%), Korea (20%), Japan (25%), Russia (20%) and US (8%), TF coils by EU (10 coils) and Japan (9 coils), in which one spare is included, all TF coil cases by Japan, all CS conductors by Japan, all CS (7 modules including a spare), PF conductor by China (65%), EU (21%) and Russia (14%), PF coils by EU (5 coils) and Russia (1 coil), all CCs by China and all feeder by China, respectively. Since the TF coil manufacture is one of long-lead items, procurement of the TF conductors have been started. More than 40 TF conductors have already been fabricated. Large-scale trials for TF coil manufacture have also been started and successful results were obtained in both EU and Japan, such as manufacture of full-scale radial plates. The trials for PF coil and CC has been done by Russia and China.