DC performance and AC loss of cable-in-conduit conductors for International Thermonuclear Experimental Reactor

A reliable prediction of AC loss is essential for the application of International Thermonuclear Experimental Reactor(ITER) cable-in-conduit conductors(CICCs);however,the calculation of AC loss of ITER CICCs is a cumbersome task due to the complicated geometry of the multistage cables and the extreme operating conditions in ITER.In this paper,we described the models developed for hysteresis and coupling loss calculation,which can be suitable for the construction of ITER magnetic system.Meanwhile,we compared the results of theoretical analysis with the SULTAN test result to evaluate the numerical model we used.In addition,we introduced the n-value and AC loss with transport current for CICCs based on the DC measurement results at SULTAN,which lays the foundation for the further study.     

AC Loss of ITER Feeder Busbar in 15MA Plasma Current Reference Scenario

Superconducting feeder busbar is a crucial component of the International Thermonuclear Experimental Reactor feeder system. AC losses including hysteresis loss and coupling-current losses (10 cycles and 1000 cycles) of the toroidal field feeder main busbar are described and calculated in detail in 15MA plasma current reference scenario in this paper. The critical current density is taken independent of magnetic field, and then the hystersis loss is evaluated; the calculated values of time constant of strands and sub-cables and the test values are approximate, and then the coupling losses are evaluted, too.     

Skin Effect in a DC Coil of Magnet during Startup Phase

1. IntroductionDC coils arc frequently tised for generation of magnetic fields in nuclear fusion study. The performanceof such a coil can be roughly divided into tit'o phases,a startup phase and a plateau phase. A direct current is established at the cud of the startup phase,then transfers to the second phase, in which the coilproduces a magnetic field ti.ith a designed strength.The electrical energy is consumed in the tit.o phases.The po\ver consumption in the second phase is inevitable and …     

Experimental validation of a lap-type joint AC loss model with an ITER correction coil conductor joint

The ITER correction coils (CC) system features shaking hands lap-type joints to interface the terminations of the conductors. The feasibility of operating plasma scenarios depends on the ability of the magnets to retain sufficient temperature and current margins. In this respect, the joints represent a possible critical region due to the combination of steady-state Joule heating from the resistance of the joint and coupling currents and connected losses in magnetic field ramped operation. Since manufacturing and testing of different joint concepts is demanding from cost and time point of view, a dedicated model has been developed based on the numerical cable model JackPot-ACDC to reproduce the performance of lap-type joints and assess the effect of possible optimization solutions. In this work, the prediction capability of the model is verified through AC loss measurements on a prototype ITER CC joint manufactured at ASIPP. The results of the experiment and model are reported and discussed.     

Magnet design of toroidal field coils for the UWMAK-Tokamak systems

The design of toroidal field coils for the UWMAK series of Tokamak reactor designs is described. These are cryogenically stable coils cooled in liquid helium to 4.2 K. Each individual turn of composite conductor of TiNb plus matrix conductor is epoxied into a groove in a thin disk structure. The magnet is divided into 12, 18 or 24 sectors; each sector is comprised of 15–20 thin disks which are spaced and bolted together to form a rigid structure with all disk surfaces exposed to cooling. The overall shape of each ‘D’ magnet sector is chosen so that only constant tension forces are present. Bending forces do occur but only near transition sections from the D to the central straight section of each coil. This method of rigid mounting should be compared with loose ‘jelly-roll’ windings on a central coil form, a more typical magnet fabrication technique. The design procedure is for the composite conductor TiNb plus copper (or aluminum) to be mounted in stainless steel (or aluminum alloy) disks. Full stability is obtained for strains less than 0.2% for steel support and less than 0.4% for aluminum supports based on stress-strain resistivity experiments in progress. The use of high purity aluminum conductor and high strength aluminum alloy structure reduces costs significantly dependent only on the orderly development of new aluminum TiNb composite conductors. The amount of TiNb is conservatively chosen to carry full current at 5.2 K although operation at 4.2 K is planned and full recovery to the superconducting state could be obtained with full current wire quantities selected at 4.3 K. This conservative choice doubles the amount of TiNb used at 8 tesla but provides an extra temperature rise of ΔT = 0.9 K above expected usual temperature excursions.Magnet safety and protection is based on the natural mutual coupling of many coils which are closely coupled to each other. If one coil loses current, the other coils increase their currents to keep the flux as constant as possible. The uncoupled flux and companion field energy would be discharged by a high voltage power supply temporarily set to discharge the one bad coil. Such sub-division and partial energy removal requires that there be substantial subdivision of coils into many separate dewars, so that problems can be isolated. An expression for the magnetic forces on sectioned toroidal field coils is given in closed form and is used to compute the shape of a specific coil. Data obtained here are shown to be in good agreement with those given by more complex procedures. The most severe structural design requirement is based on simultaneous loss of current in two adjacent sectors. The remaining sectors attempt to straighten out into a solenoid which compresses the structure between coils except beside the bad coil or coils where tension might exist. Such current loss in two adjacent sectors is considered an extremely unlikely occurrence since the discharge procedure mentioned above takes place in less than 1 min so that simultaneous refers to a 1 min overlap. Because of such rapid amelioration of the causes of current change and flux motion, no temperatures can exceed room temperature during the orderly shutdown of one or two coils. In general, the study illustrates that fully stable magnets using composite conductors should be engineered without major uncertainties according to straightforward scientific concepts. While subsequent designs will undoubtedly include improvements there is no reason to expect that superconductivity implies venturesome unknown TF coil performance.     

Test and Analysis of China's First Short Conductor Sample for ITER Toroidal Field Coils

In the framework of the ITER Qualification Tests, the first China TF conductor sample (CNTF1) was tested at the SULTAN facility. The sample was made of two TF conductor sections manufactured from identical internal stannum strands provided by the Oxford Superconducting Technology Company (OST). In order to evaluate the conductor performance, the current sharing temperature (Tcs) was measured at specified electromagnetic load cycling steps. Both conductor sections of the CNTF1 sample showed identical performance. Tcs was 7.2 K before cycling loading, and 6.9 K even after 950 cycles, without significant degradation, which substantially exceeds the ITER requirement of 5.7 K. The tests of the CNTF1 conductor sample showed that the electromagnetic cyclic load exhibited a negligible effect on the conductor performance. The coupling time constant for AC loss was 214 ms and 71.52ms before and after the cycling load, respectively. The test results of the sample are compared with the strand performance and parameter model analysis.     

The European Nb3Sn advanced strand development programme

Strands relevant for fusion with high critical current densities and moderate hysteresis losses were developed and already produced on industrial scale. Based on these achievements EFDA-CSU Garching has launched a Nb₃Sn strand development and procurement action inside Europe in order to assess the current status of the Nb₃Sn strand production capability. All six addressed companies have replied positively to the strand R&D programme which includes the three major Nb₃Sn production techniques namely the bronze, internal-tin and powder-in-tube (PIT) route. According to the strand requirements for the ITER TF conductor a critical current density of 800 A/mm² (at 12 T, 4.2 K and 10 μV/m) and overall strand hysteresis losses below 500 kJ/m³ have been specified as the minimum guaranteed strand performance.The second major objective of this programme is to motivate the strand manufacturers to develop and design high performance Nb₃Sn strands optimised for the ITER conductor. For this purpose, a target critical current density of 1100 A/mm² has been added to the specification. This paper describes the strategy behind the strand development programme, the actual status of the strand production as well as first preliminary results obtained from the strand suppliers.     

The AC losses measurement and analysis of superconducting NbTi CICC for HT-TU superconducting Tokamak

Superconducting TF and PF coils have been measured in SULTAN test facility. Segregated copper strands are included in four NbTi CICC and this is a technical innovation. Two AC losses measurement methods, calorimetric and electromagnetic methods, have been used in the experiments, and a broad frequency range (from 0.05 Hz to 6 Hz) is covered in sample test. The purpose of this experiment was to investigate AC losses of TF and PF CICC conductor including segregated copper and to check the design of PF and TF CICC coated with different resistive barriers (Pb-30Sn-2Sb and Ni plating on NbTi strands).     

10 MeV/50 kW脊型加速器输入耦合器的研制

10 MeV/50 kW脊型加速器是一种新型大功率电子辐照加速器,其加速腔中所需射频功率高达100 kW,为此专门研制了高功率输入耦合器。该耦合器主要由陶瓷窗、内外导体及耦合环组成,通过等效电路分析以及仿真计算确定了最终结构。设计采用了可独立拆卸的平板型陶瓷窗和可旋转调节的耦合环,以便于进行脊型加速器调试,并在内外导体和耦合环中设计了水冷回路带走功率传输产生的热量。经过测试,该输入耦合器可在0～2.2范围内调节耦合度,并成功向脊型谐振腔中注入了100 kW的脉冲峰值功率。     

High current superconductors for DEMO

In the assumption that DEMO will be an inductively driven tokamak, the number of load cycles will be in the range of several hundred thousands. The requirements for a new generation of Nb₃Sn based high current conductors for DEMO are drafted starting from the output of system code PROCESS. The key objectives include the stability of the DC performance over the lifetime of the machine and the effective use of the Nb₃Sn strand properties, for cost and reliability reasons. A preliminary layout of the winding pack and conductors for the toroidal field magnets is presented. To suppress the mechanism of reversible and irreversible degradation, i.e. to preserve in the cabled conductor the high critical current density of the strand, the thermal strain must be insignificant and no space for micro-bending under transverse load must be left in the strand bundle. The “react-and-wind” method is preferred here, with a graded, layer wound magnet, containing both Nb₃Sn and NbTi layers. The implications of the conductor choice on the coil design and technology are highlighted. A roadmap is sketched for the development of a full size prototype conductor sample and demonstration of the key technologies.     

High temperature superconductors for the ITER magnet system and beyond

The use of high temperature superconductor (HTS) materials in future fusion machines could increase the efficiency drastically, but strong boundary conditions exist. To outline the prospects, challenges and problems, first the benefit of using HTS materials is estimated considering the saving in cryogenic power. Next, it is demonstrated that industrial available HTS materials can be used for fusion today. For this purpose, we give a short summary of results that have been obtained from an ITER conform 70 kA HTS current lead that was designed, built and tested by the Forschungszentrum Karlsruhe and the CRPP Villigen in the frame of the European Fusion Technology Programme and in cooperation with industry. This current lead consists of an HTS part that covered the temperature range from 4.5 to 70 K and a conventional part, making the connection to room temperature. Because the HTS part had no ohmic losses and poor thermal conduction, the refrigerator power necessary for cooling the current lead was reduced drastically. The saving factor could be calculated to be 5.4 at zero current and 3.7 at 68 kA. The current lead could even be operated at 80 kA and with respect to safety criteria of ITER, a complete loss of He flow was simulated showing that the HTS current lead could hold a current of 68 kA for 6 min without active cooling. These results demonstrate that today existing HTS materials can be used in ITER for current leads or bus bar systems.For fusion machines beyond ITER, the development of an HTS fusion conductor would be the key to operate the complete magnet system at higher temperatures. The option of developing fusion conductors based on Bi-2223 and YBCO are briefly discussed. For a success of such conductors, the AC loss optimisation is crucial.     

上海光源二期工程的垂直发射度研究

上海光源二期工程正在设计一个新的磁聚焦结构,它包含双斜插入件、超导二极铁以及超导扭摆器等新的元件。光谱亮度是表征同步辐射光源性能的一个重要参数,通过降低垂直发射度的方式来提高亮度是一种简便可行的方法。首先分别模拟和计算了各类磁铁准直误差对垂直发射度的影响,然后采用奇值分解法校正了误差引起的闭轨畸变,最后使用60个斜四极铁来校正垂直发射度。结果表明,在上海光源二期工程的磁铁准直公差与目前正在运行的上海光源相同的条件下,六极铁垂直准直误差对垂直发射度的影响最大;用60个斜四极铁来校正垂直发射度,能使耦合度保持在0.5%以下。     

Status of the ITER magnets

The first 2 years of the ITER IO has seen substantial progress towards the construction of the magnets, in three main areas. Firstly, the design has been developed under the conflicting constraints to minimise construction costs and to maximise plasma physics performance. Building construction momentum while updating the design to take account of new physics assessments of the coil requirements has been challenging. Secondly, with a stabilising design, it has been possible for the Domestic Agencies to launch the first industrial procurement contracts. And thirdly, critical R&D to confirm the performance of the Nb3Sn cable in conduit design is proceeding successfully.The design consolidation has been accompanied by design reviews involving the international community. The reviews conducted by magnet experts have enabled a consensus to be built on choosing between some of the design options in the original ITER basic design in 2001. The major design decisions were to maintain the circular Nb₃Sn conductor embedded in radial plates for the toroidal field (TF) coils and to maintain NbTi-based conductors for the PF coils. Cold testing, at low current, is also being introduced for quality control purposes for all coils.     

The bearing strength of steel coupling beam-reinforced concrete shear wall connections

Increasingly, engineers are designing hybrid and mixed building systems of structural steel and reinforced concrete to produce more efficient structures than can be realized using either material alone. In particular, hybrid coupled shear wall of them are known to be efficient lateral load resisting system. However, due to lack of information, current design equations to compute the bearing strength of steel coupling beam–wall connections in a hybrid coupled shear walls are tacit about cases in which the beams have connection details to the walls that include stud bolts and horizontal ties in hybrid coupled shear walls. There were carried out experimental and analytical studies on steel coupling beam–wall connections in a hybrid wall system. Experimental study was carried out to verify the bearing strength of steel coupling beam–wall connections. The test variables included the reinforcement details that confer a ductile behavior on the steel coupling beam–wall connection, i.e., the stud bolts and the horizontal ties in the steel coupling beam–wall connections. The equations proposed in this study to predict strength for steel coupling beam-reinforced concrete shear wall connections were in good agreement with both our test results and other test data from the literature.     

聚变-裂变混合堆水冷包层中子物理性能研究

研究直接应用国际热核聚变实验堆（ITER）规模的聚变堆作为中子驱动源,采用天然铀为初装核燃料,并采用现有压水堆核电厂成熟的轻水慢化和冷却技术,设计聚变-裂变混合堆裂变及产氚包层的技术可行性。应用MCNP与Origen2相耦合的程序进行计算分析,研究不同核燃料对包层有效增殖系数、氚增殖比、能量放大系数和外中子源效率等中子物理性能的影响。计算分析结果显示,现有核电厂广泛使用的UO₂核燃料以及下一代裂变堆推荐采用的UC、UN和U₉₀Zr₁₀等高性能陶瓷及合金核燃料作为水冷包层的核燃料,都能满足以产能发电为设计目标的新型聚变 裂变混合堆能量放大倍数的设计要求,但只有UC和U₉₀Zr₁₀燃料同时满足聚变燃料氚的生产与消耗自持的要求。研究结果对进一步研发满足未来核能可持续发展的新型聚变-裂变混合堆技术具有潜在参考价值。     

A Synchronization Pulse for the Princeton-Pennsylvania Accelerator

The basic synchronizing pulse in the P.P.A., tying the injection pulse and the R. F. to the magnetic field, is derived from the total current flowing through one of the Accelerator magnets. This pulse is generated in a biased toroidal coil wound on a supermalloy core, by the magnetic field H(t) created by the magnet current in a coaxial conductor. This method has provided us with a synchronization signal pulse with excellent long term stability and very little time-jitter. Part of the time-jitter may be attributed to the variations of dH/dt at the time of the reversal of the magnetization of the core due to variations of Imin in the magnets. A method has been developed to effectively cancel out the dH/dt effect in the supermalloy core.     

超导磁体气冷电流引线的优化设计

从超导磁体气冷电流引线的经典微分方程出发,将电流引线分为很少的几段,提出了一种较为精确计算电流引线长横比及由电流引线末端流入低温容器热量的计算方法。并以黄铜为例计算了电流引线的长横比和流入低温容器的热量。     

CSNS/RCS陶瓷真空盒热特性及振动研究

陶瓷真空盒作为中国散裂中子源（CSNS）快循环同步加速器（RCS）真空系统的关键部件,能避免RCS二极、四极交流磁铁因快速变化的磁场而产生的涡旋电流。因安装空间限制,RCS陶瓷真空盒支架固定在磁铁线圈上。在CSNS/RCS交流磁铁长时间加电测试中,出现陶瓷真空盒断裂、真空破坏的情况。为避免后期出现类似问题,从磁铁发热进而引起陶瓷真空盒不均匀升温的角度出发,对陶瓷真空盒的热特性进行了分析,同时基于双目视觉测量技术,对陶瓷真空盒的振动情况进行了监测,针对部分真空盒水平方向振动异常的问题,确定其影响因素为快卸链条的磁导率超标。最后开展了陶瓷真空盒的支架减振技术研究。     

Design practice and operational experience of highly irradiated,high performance normal magnets

The fundamental limitations, design practice, and operating experience of high-stress and highly irradiated normal magnets are discussed. Magnet performance is limited by mechanical stresses, temperature limits, oxidation, and erosion. Electrical performance is limited by dielectric breakdown, flashover, and tracking. Degradation of mechanical and electrical properties of metals and insulators by electromagnetic and neutron irradiation is discussed. The failure mechanisms due to irradiation include increased conductor resistance, destruction of chemical bonds, electrolysis, and photoconductivity. The operating experience of high-performance magnets at magnet laboratories, accelerators, and fusion experimental facilities is discussed.     

聚变-裂变混合堆程序开发及验证

针对聚变-裂变混合堆设计研究中原有燃耗计算程序MONK9A耗时长等问题,利用MCNP和SCALE5.1程序包中的Origen-s程序开发出1套可用于先进反应堆设计的燃耗耦合程序MOCouple-s.选取了压水堆燃耗基准题、ADS基准题对MOCouple-s程序进行了验证,结果表明,MOCouple-s程序关于反应性和核素成分的计算结果与实验测量结果和其他程序的计算结果符合良好,且在某些计算结果、参数设置、自动化执行等方面优于国内外类似程序.利用MOCouple-s程序对MONK9A程序在混合堆燃耗计算上的适用性进行了验证,结果差别不大,证明MONK9A程序用于混合堆初步研究设计得到的燃耗计算结果是可靠的.