50 kA超导变压器杜瓦及高温超导电流引线的设计与优化

CICC超导导体性能测试用50 kA超导变压器由初级线圈和次级线圈组成,初级线圈浸泡在4.2 K液氦低温杜瓦中,次级线圈为CICC导体采用4.2 K/354 637 Pa超临界氦迫流冷却,液氦和超临界氦均由500 W/4.5 K制冷机提供,变压器低温杜瓦的理论液氦蒸发率为1.52 L/h。为减少电流引线漏热,超导变压器采用B i-2223/AgAu高温超导(HTS)二元电流引线,并且在颈管中部设计了一个新型的直接用液氮冷却的热截流装置来截断电流引线高温端的热流;最后对铜电流引线部分进行了尺寸优化计算,得到最佳截面积和直径分别为28 mm2和6 mm。     

Superconducting magnet for K-500 cyclotron at VECC, Kolkata

K-500 superconducting cyclotron is in the advanced stage of commissioning at VECC, Kolkata. Superconducting magnet is one of the major and critical component of the cyclotron. It has been successfully fabricated, installed, cooled down to 4.2 K by interfacing with LHe plant and energized to its rated current on 30th April, 2005 producing magnetic field of 4.8 T at median plane of cyclotron. The superconducting magnet (stored energy of 22MJ) consists of two coils (α and β), which were wound on a sophisticated coil winding machine set-up at VECC. The superconducting cable used for winding the coils is multi filamentary composite superconducting wire (1.29 mm diameter) having 500 filaments of 40 μm diameter Nb-Ti in copper matrix which is embedded in OFHC grade copper channel (2.794 mm × 4.978 mm) for cryogenic stability. The basic structure of coil consists of layer type helical winding on a SS bobbin of 1475 mm ID × 1930 mm OD × 1170 mm height. The bobbin was afterwards closed by SS sheet to form the LHe chamber. The total weight of the coil with bobbin was about 6 tonne and the total length of the superconducting cable wound was about 35 km. Winding was done at very high tension (2000 PSI) and close tolerance to restrict the movement of conductor and coil during energization. After coil winding, all four coils (two each on upper and lower half of median plane of cyclotron) were banded by aluminium strip (2.7 mm × 5 mm) at higher tension (20,000 PSI) to give more compressive force after cool down to 4.2 K for restricting the movement of coil while energizing and thereby eliminating the chances of quench during ramping of current.After completion of coil winding by October, 2003, cryostat assembly was taken up in house. The assembly of cryostat (13 tonne) with support links (9 Nos.) refrigeration port, instrumentation port, helium vapour cooled current loads, etc. was completed by June, 2004. Meanwhile assembly of magnet frame was taken up and the cryostat was positioned in the magnet frame with proper alignment by August, 2004. After installation of cryostat on magnet, the cryostat was connected to the helium refrigerator/liquefier, having refrigeration capacity of 200 W and 100 l/h in liquefier mode with LN2 pre-cooling. The cryogenic delivery system supplying the liquid helium and liquid nitrogen to the superconducting magnet was successfully commissioned in November, 2004. The cool down of the cryostat to 10 K took around 8 days following which the LHe was filled in the cryostat (300 l) on 15th January, 2005. Subsequently the superconducting coils (α and β) were energized by two DC current regulated power supplies (20 V, 1000 A, 10 ppm stability) with slow and fast dump resistors connected externally across the superconducting coils for protection of coils at the time of power failure and quench.The paper describes the intricacies involved in coil winding, winding set-up, assembly of cryostat, cooling down the superconducting coils, filling by LHe and energization to rated current. The paper also highlights the operating experience of superconducting magnet and related test results.     

ITER CC导体接头测试装置设计与研制

根据国际热核实验反应堆(ITER)校正场线圈(CC)导体接头低温电阻的测试要求,设计并研制了一套用于超导导体接头的低温测试装置。该装置主要包括10 kA超导变压器、低温测试杜瓦、磁体失超保护系统和数据采集系统等。超导变压器的初级线圈及次级线圈采用LHe浸泡的方式进行冷却。超导变压器初级线圈电流引线采用常规铜电流引线,为增加铜的传热面积,采用编织铜引线代替铜棒引线。初级线圈外接磁体电源,利用电磁感应原理,在次级回路感应出超导导体接头测试所需的电流。已经成功进行了一次CC导体接头的低温实验,接头电阻的测试结果分别为8.4纳欧姆和9.3纳欧姆。     

Superferric quadrupoles for FAIR Super FRS energy buncher

The quadrupole magnets for FAIR Super FRS energy buncher have large usable aperture, high magnetic pole-tip field and high gradient field quality. The iron-dominated magnets with superconducting coils have to be used in this application. The NbTi coil, laminated iron, and support structure of about 22 tons is immersed in liquid helium. The 4.5 K helium chamber is completely covered with a thermal shield cooled by helium at 50–80 K on its outer and inner surface. The helium chamber and thermal shield is enclosed in a vacuum shell.The paper presents design details of the long quadrupole. Coupled thermal, magnetic and structural analysis was carried out to design the magnet iron, magnet coil, helium vessel and support links and ensure the required gradient field quality is achieved. The paper also presents the design of support links and outer vacuum chamber.     

35 kJ高温超导磁储能(SMES)的热输运实验研究

研制了中国首台高温超导磁储能直接冷却系统,该系统不使用低温液体(液氦、液氮).在10-3Pa的真空度下,高温超导磁体线圈由1台单级GM制冷机从室温293 K冷却到19 K,Bi2223电流引线由另一台制冷机冷却到77 K以下.整个系统在通140 A直流电流的时候产生了4.5 T的磁场.系统连续运行480 h(20 d),磁体和低温系统各参数动态特性良好.实验研究表明,控制系统的漏热,优化磁体内部导冷结构,有效减少热传导部件的接触界面热阻是制冷机直接冷却高温超导磁体的关键技术.     

40-T混合磁体外超导线圈迫流氦流动摩擦系数分析

40-T混合磁体外超导磁体使用4.5 K超临界氦进行迫流冷却。迫流氦在管内电缆导体(CICC)内的流动过程受到摩擦阻力的影响会造成一定的压降和热量产生,同时由外界带来的热量也会由迫流氦带走来让磁体保持在超导温区。使用了超导磁体实际运行过程中的实验数据计算不同导体结构下雷诺数与摩擦系数的变化关系,利用Katheder经验公式对实验的摩擦系数进行了重新拟合,给出了适用于该导体摩擦系数的经验公式。     

General atomic's superconducting high field test facility and initial performance

General Atomic has established a high field test facility whose primary mission is to investigate the J-B-T and stability performance margins of commercial NbTi superconductor in the 10 tesla, 4.2 K region. This work is part of the overall DOE/MFE/MAGNETIC SYSTEMS effort to provide an adequate technological base for construction of superconducting toroidal field coils for the next generation of large tokamak fusion devices. The principal components of the facility are the coil/cryostat assembly, the helium refrigerator-liquefier/compressor system, and the gaseous helium recovery and storage system. The epoxy impregnated, layer wound main background field coil generates 8 tesla within its 40 cm diameter bore. The insert background field coil was layer wound with cooling channels provided by "barber pole" mylar conductor insulation. Ten tesla is generated within its 22 cm bore. The initial performance of the facility will be discussed. Future testing calls for operating test coils with implanted heating elements to simulate mechanically induced perturbations. The normal zone growth and recovery behavior will be observed for various disturbance energies. This data will then be compared with results obtained from the transient recovery analysis developed at General Atomic.     

Modelization of the thermal coupling between the ITER TF coil conductor and the structure cooling circuit

The ITER Toroidal Field (TF) coils are required not to quench during the most demanding event: a plasma disruption followed by a fast discharge of the Central Solenoid (CS), the Poloidal Field (PF) coils and the Correction Coils (CC). This event creates large heat deposition in the ITER magnet stainless steel structures in addition to the conductor AC losses. In order to prevent quench occurring in the TF conductor, cooling channels, implemented in the TF coil structure (TFCS), have to remove a large fraction of the heat deposited. The first integrated TF and structure mock-up has been manufactured and then tested in the HELIOS cryogenic test facility (CEA Grenoble) to determine the thermal coupling between the TFCS and the TF conductor, both actively cooled by supercritical helium at 4.4 K and 5 bar. It consists in a stainless steel casing, a cooling pipe glued with resin in the casing groove, winding pack (WP) ground insulation, a radial plate and a copper dummy cable-in-conduit-conductor (CICC). Steady state as well as transient thermal characterizations have been completed in May 2015. Simulation results by thermal hydraulic codes (VENECIA/SuperMagnet) and some of the experimental data are presented and discussed. The thermal coupling between the helium in the cooling tube and the TF coil structure is then modelled as an equivalent heat transfer coefficient in order to simplify the thermal hydraulic (TH) models. Comparison between simplified coupling and detailed coupling is presented.     

Development of a Superconducting Magnet System with Zero Liquid Helium Boil-off

A homogeneous magnetic field superconducting magnet with a cold bore of 250 mm and a central field of 4.3 T has been designed, manufactured, and tested with zero liquid helium boil-off. As a result of magnetic field homogeneity considerations, the magnet is composed of three coaxial coils: one main coil and two compensation coils. All coils are connected in series and can be charged with a single power supply. The magnetic field homogeneity is about ±3.0 % from ?200 mm to 200 mm in axial direction with 86 mm in diameter. The magnet can be operated in persistent mode with a superconducting switch. A two-stage GM cryocooler with a capacity of 1.5 W at 4.2 K was used to cool the superconducting magnet. The cryocooler prevents the liquid helium from boiling off and leads to zero helium loss during static operation. The magnet can be operated in liquid helium circumstance by cooling the gas helium with the cryocooler without additional supply of liquid helium. Under this condition, the magnet is successfully operated up to 4 T without quench. The magnet system can be generating 0.25 L/h liquid helium with the cryocooler by supplying the gas helium without loading the magnet. In this paper, the magnet design, manufacture, mechanical behavior analysis, and the performance test results of the magnet are presented.     

A superconducting coil indirectly cooled by forced helium flow

A small superconducting coil is indirectly cooled by a forced flow of helium. The coil, wound from Nb-Ti-Zr multifilament superconducting composite, is 15 mm id, 24 mm od and 30 mm long. The maximum central field is 30.3 kG at 4.2 K. Contact between the cooling tube and the coil is achieved using grease.The experimental results are expressed by a relation of critical current and energizing rate. Typical transient temperatures of the coil and coolant during energizing and after quenching are presented.The analysis shows the design of coils of this type is possible using hysteresis loss and heat conduction analysis.     

EAST超导托卡马克热负荷波动对低温系统液氦槽的影响

EAST超导托卡马克的纵场和极向场磁体均采用NbTi超导材料,由3.8 K超临界氦冷却.在托卡马克实验运行时,极向场的放电脉冲和等离子体破裂产生的交流损耗带来的热负荷增加,经过超临界氦流带到低温系统控制阀箱内的液氦槽和过冷槽,造成槽内的液氦蒸发量增加.蒸发的氦回到制冷机中,从而影响制冷机的稳定运行.通过对实际超临界管道和液氦槽、过冷槽中换热过程建立换热模型,进行热工分析,分析液氦槽和过冷槽中的压力等参数的变化,指导低温系统的设计.     

A 10 tesla cryomagnetic system for neutron scattering experiments

A cryomagnetic system is described in which the first main component is a cryostat providing variable temperatures and the second a superconducting coil. The cryostat enables the coil to operate at either 4.2 K or 2.16 K, and allows a sample of diameter 10 mm, height 10 mm, to be brought to temperatures varying from 1.5 K to 300 K.The magnet is an asymmetrical split coil with a vertical magnetic axis. Aluminium windows provide access vertically over 15°, horizontally over 340° to a bore of useful diameter 32 mm. The superconducting magnet is wound from multifilamentary NbTi and Nb₃Sn wires and provides a central field of 8.7 T at 4.2 K and 10 T at 2.16 K.     

稳态混合磁体装置低温系统过冷槽的设计与优化

40 T稳态混合磁体装置的外超导磁体需要4.5K、5×105Pa、18 g／s超临界氦迫流冷却,拟采用盘管换热器将从制冷机出来的氦冷却至超临界状态.首先对氦制冷机进行混合模式的热力学分析,确定过冷槽中盘管换热器的进口压力及温度,进而提出阶梯管径理论,根据工程要求设计并优化盘管换热器,得出盘管换热器的盘绕方式及尺寸;最后...     

合肥超导托卡马克装置首次致冷

１９９４年７月１２－２２日期间合肥超导托卡马克装置ＴＨ－７首次低温调试。４Ｋ温区冷重高达１４Ｔ的超导环场磁体经９６ｈ致冷，用二相Ｈｅ保冷３昼夜。超导线圈内外侧设侧设置的热辐射屏重约８Ｔ，用液氦致冷，约６０ｈ冷至８０Ｋ。磁体共励磁二次，最大电流达４６５０Ａ，相应的环场为２．２Ｔ，超导体的最高场为３．７Ｔ。     

Design analysis of a solid nitrogen cooled “permanent” high-temperature superconducting magnet system

Potential performance advantages of a solid nitrogen cooled “permanent” high-temperature superconducting (SN2/HTS) magnet system over a liquid helium cooled low-temperature superconducting (LHe/LTS) system are explored. The SN2/HTS system design includes a second solid heat capacitor that cools a radiation shield. Recooling of the heat capacitors is performed with a demountable cryocooler. The SN2/HTS system offers both enhanced stability and improved portability over a LHe/LTS system.Design codes are constructed to compare the SN2/HTS system design with a LHe/LTS design for a general permanent superconducting magnet system employing a room temperature bore. The codes predict the system volume and mass that should be expected for a given set of design requirements, i.e. field strength and bore size, and a given set of conductor properties. The results indicate that present HTS conductor critical current and index are not yet sufficient for producing SN2/HTS systems of a size that is comparable with that expected for a LHe/LTS system; however, the conductor properties of Bi2223/Ag have been consistently improving, and new HTS conductors are expected to be developed in the near future. The codes are used to determine the minimum Bi2223/Ag conductor performance required for a SN2/HTS system to be competitive with a LHe/LTS system.     

Sweeping a persisting superconducting magnet with a transformer

A method for sweeping a persisting superconducting magnet is described. The field sweep is achieved by including in the superconducting loop of the magnet a coil which acts as the secondary coil of a transformer. Variation of the current in the primary coil of the transformer, controlled from outside the cryostat, causes the field-sweeping action through flux-linking with the superconducting loop. Compared by the ratio of the magnet's inductance to the transformer's inductance. The advantages of using an all-metal vacuum-tight superconducting feedthrough are discussed.     

Hydraulic behavior of forced-flow cooled superconducting coils for the large helical device

The large helical device (LHD) has been operated since 1998 and the 13th experimental campaign was conducted in 2009. Before final assembling, cool-down and excitation tests for the Inner Vertical (IV) field coil, which is one of the LHD poloidal field coils, were carried out in 1995. This coil, which consists of a cable-in-conduit conductor, (CICC) is cooled by the forced-flow of supercritical helium. During the tests of the IV coil, hydraulic characteristics, such as flow distribution among cooling channels and friction factors, were measured. In this paper, the consistency of the behavior of the IV coil will be presented and comparison with other fusion devices using superconducting coils will also be made at not only cryogenic temperatures but also at room temperature.     

Development of a cryogenic test bed for high amperage critical current measurement on high temperature superconductor wire

Many areas of research have benefited from the application of conduction-cooled superconducting magnet technology. The middle and small-scale magnets immersed in the liquid helium will be replaced by the easy-operating conduction-cooled superconducting magnet due to convenient operation, lower operating cost and easy for user. For the goal of superconducting magnet applications in the advanced testing for high temperature superconducting (HTS) wire and sample coils, a wide bore conduction-cooled superconducting magnet with available warm bore of ?186 mm and center field of 5-6 T for background magnetic field applications was designed, fabricated and tested. The system allows measurements to be performed in a repeatable and reliable fashion. In order to support the high stress in magnet, the detailed finite element (FE) analysis with electro-plastic model is proposed. The sample cryostat is designed with cryofree. It includes two GM cryocoolers. The detailed design, fabrication and thermal analysis are presented in the paper.     

Extending an internally cooled superconducting magnet to higher fields

An internally cooled superconducting (ICS) magnet was built and tested earlier at Oak Ridge National Laboratory (ORNL), and its stability margin as a function of operating fields was measured at an ambient helium temperature of 4.2 K. In the experiment reported here, we retested this magnet with lower bulk helium temperatures. The stability margins of the magnet as a function of temperature were measured. The results demonstrate clearly the flexibility offered by an ICS magnet: The stability margin can be improved substantially or the field output can be extended without sacrificing the stability margin simply by feeding the magnet with lower temperature helium. The analysis made in a previous paper on extended field operation of an ICS magnet is thus confirmed.     

A NbTi 10T 388mm bore magnet working at 1.8K in pressurized superfluid helium

A new high field test facility has been constructed for overall property measurements of the conductors developed for the superconducting coils of the TORUS II Tokamak project proposed by the EURATOM-CEA Association. This facility features a dc background field of 10 T in a useful volume of 338 mm in diameter and super-imposed pulsed fields of various configurations.The present paper describes the design, construction and operation of the 10 T field coil system in its pressurized superfluid helium cryostat.