Development of HTS Current Leads for the ITER Project

Bauer, P.; Ballarino, A.; Devred, A.; Ding, Kaizhong; Dong, Yanfeng; Niu, Erwu; Du, Qingqing; Gung, C.; Han, Qiuying; Heller, R.; Huang, Xiongyi; Ichihara, T.; Lee, S; Li, J; Liu, C; Liu, CL; Lü, Kun; Mitchell, N.; Song, Yuntao; Spina, Tiziana; Ran, Qingxiang; Taylor, T. Matthew; Yamada, S.; Yang, Y.; Zhou, Teng

doi:10.1088/1757-899x/756/1/012032

Cited by 32 publications

(7 citation statements)

References 20 publications

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“…Several pairs of high-capacity current leads (CLs), with current ratings above 10 kA, have been designed and built for fusion and other high-field magnet applications. These CLs, for example [18] [19] [20] [21] [22], use a 'binary' approach, with a resistive (typically copper) upper section and High Temperature Superconducting (HTS) lower section to minimize the heat load at the low-temperature end of each CL. The resistive section spans from room temperature to an intermediate temperature, typically between 40 K and 80 K, while the HTS section extends from the intermediate temperature to the magnet's operating temperature, which is usually below 20 K. A key consideration when choosing between design options is the type and quantity of cryogen needed to operate the CLs.…”

Section: A Backgroundmentioning

confidence: 99%

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50-kA Capacity, Nitrogen-Cooled, Demountable Current Leads for the SPARC Toroidal Field Model Coil

Fry,

Zhukovsky,

Wolf

et al. 2024

IEEE Trans. Appl. Supercond.

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This paper presents design, fabrication, and operational results for a novel pair of binary Current Leads (CLs). The CLs were purpose built for the SPARC Toroidal Field Model Coil (TFMC) Test Facility at the MIT Plasma Science and Fusion Center. The approximately 3 m tall CLs demonstrate stable operation at current ramp rates up to 50 kA/s and steady-state currents of 50 kA from ambient temperature power supplies to the facility's 20 K test environment.Each CL can be divided into three main parts: an upper copper heat exchanger (HEX) cooled with gas nitrogen (GN2) which connects to room temperature water cooled power supply (PS) bus; a central liquid nitrogen (LN2) boiling chamber (BC) which vents into the HEX; and a lower Rare Earth Yttrium Barium Copper Oxide (REBCO) Section.The CLs have three distinguishing features. First, the BCs provide high surface area, maintaining <1 K temperature difference between their surfaces and the nucleate boiling LN2 they contain. Second, each REBCO section is composed of six "petals" that could be individually qualified to verify performance prior to installation. Third, indium seals were used throughout the assembly to simultaneously provide electrical continuity for current transfer and hermetic sealing, while enabling fabrication and assembly without need of the lengthy braze or electron beam welding qualification processes typically required for alternative designs.The modular approach was adopted to meet the aggressive schedule of the TFMC project. As a further hedge against design uncertainties, the leads were designed to permit sub-cooled operation at lower LN2 boiling pressure, and thus lower temperature which significantly increases the temperature margins within the REBCO Section.The CLs were designed and built within 1.5 years and used successfully to deliver 40.5 kA of current to the SPARC TFMC. Since that time they have been thermally cycled over 10 times and operated successfully at both 1 atm and 0.65 atm while transmitting steady state 50 kA current following transient current ramp rates of up to 50 kA/s.

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Section: A Backgroundmentioning

confidence: 99%

“…Design recommendations from the ITER CLs for contact area with the PS were followed which include: current density ~2-3 A/mm^2 to prevent excessive heating and bus surface contact <0.5 A/mm^2 [18]. Final values at 40.5 kA were 2.5 A/mm^2 and 0.5 A/mm^2, respectively.…”

Section: Room Temperature Current Terminalmentioning

confidence: 99%

50-kA Capacity, Nitrogen-Cooled, Demountable Current Leads for the SPARC Toroidal Field Model Coil

Fry,

Zhukovsky,

Wolf

et al. 2024

IEEE Trans. Appl. Supercond.

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“…The temperature at the interface is defined as T f . Then, the equivalent thermal conductivity normalized to either side of the interface can be deduced simultaneously from equation (13). keq i−1 and keq i are the equivalent thermal conductivity normalized to the bottom and upper cells, respectively, and their expressions are given in equations ( 14) and (15).…”

Section: Equivalent Thermal Conductivitymentioning

confidence: 99%

“…HTS binary current leads were first proposed by Mumford in 1989 [3]. In the past few years, HTS binary current leads have been widely applied, not only in large-scale systems, such as particle accelerators [4][5][6][7] and fusion devices [8][9][10][11][12][13], but also for smaller isolated magnets, such as superconducting magnetic resonance imaging (MRI) magnets [14,15], high-field magnet system [16][17][18][19][20][21] and other special test facilities [22][23][24][25][26][27][28][29][30]. The typical structure of binary current leads comprises two parts: a hightemperature portion made by a normal conductor and a lowtemperature portion made by an HTS and a normal metal shunt.…”

Section: Introductionmentioning

confidence: 99%

The design of YBCO binary current leads and its electromagnetic-thermal coupling analysis based on PEEC and finite volume method

Zheng

Liu

Song

et al. 2023

Supercond. Sci. Technol.

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A superconducting magnet system is developed for the application of high frequency gyrotrons at XXX. The operation cost for the magnet is dominated by refrigeration power. To reduce the heat load for cryogenic system, a pair of YBCO binary current leads is designed in consideration of the industrial concentration on type II high temperature superconducting (HTS) YBCO material. In this paper, a simulation model is proposed to perform the electromagnetic-thermal coupling analysis of these YBCO binary leads under different operation conditions by combining Partial Element Equivalent Circuit (PEEC) method and Finite Volume Method (FVM). The simulation code can improve computational efficiency and enable high-accuracy coupling between the electromagnetic field and heat transfer process. Under steady state, the heat leakage at 4.2 K cold end of YBCO binary leads depends mainly on the geometric parameters of YBCO tape, especially the cross-sectional area of the copper layer in YBCO tape. The cooling mode and liquid helium level also have a significant impact on the heat leakage level. The optimal outer diameter of the normal copper section is identified, and the optimum value is largely influenced by the effective cooling power imposed on the cold end of the normal copper section. Under transient state, the simulation for charging process and the loss of cooling accident are performed, along with the detailed analysis of the electromagnetic-thermal response features of the leads under these conditions. The results indicate that the YBCO binary current leads possess high thermal stability and an ample time margin for the magnet system to be demagnetized.

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“…In the past three decades, different cooling concepts of HTS CLs have been studied [13], and they are generally classified into two categories according to the resistive part of the first stage. One type is based on the VCCL part with an HTS section for high-current applications, which was developed for the accelerator and fusion machines, such as Tevatron [14], LHC [15,16], JT-60SA [17] and ITER [18], and recognized as a standard technology for large-scale applications [19].…”

Section: Cls With An Hts Sectionmentioning

confidence: 99%

Theoretical analysis of conduction-cooled current lead for superconducting magnet

Zong,

Shimizu

2023

Supercond. Sci. Technol.

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CCCL is a typical CL type to energise SC magnets from room to cryogenic temperatures (<100 K) for its simplicity and reliability, but causes a relatively large heat leak (∼50 W kA−1 from 300 K) compared to the heat leak (∼1.0 W kA−1 from 300 K to liquid helium) of VCCLs, which necessitates a comprehensive understanding of designers and users. However, systematic studies on CCCLs are still lacking up to now. This study starts from the differential equation governing heat conduction and generation in CCCLs and firstly derives a completely exact theoretical solution by adopting the WFL law for thermal conductivity and electrical resistivity with temperature dependence. The solution facilitates the CCCL design optimisation to achieve the minimum heat leak, which is determined only by the temperature range but independent of both materials and geometrical parameters. Practical optimum designs are concerned with material properties and approached by calculating a shape factor to determine the conductor length and cross-sectional area, which is detailed and illustrated in this paper. Furthermore, the practical behaviours at low and excess currents can also be mathematically deduced, and the corresponding heat leaks are found to rely on materials but not on geometrical parameters. This paper also describes the agreements between the theoretical analysis and the numerical simulation and comparison with material properties of the non-WFL law.

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Development of HTS Current Leads for the ITER Project

Cited by 32 publications

References 20 publications

50-kA Capacity, Nitrogen-Cooled, Demountable Current Leads for the SPARC Toroidal Field Model Coil

50-kA Capacity, Nitrogen-Cooled, Demountable Current Leads for the SPARC Toroidal Field Model Coil

The design of YBCO binary current leads and its electromagnetic-thermal coupling analysis based on PEEC and finite volume method

Theoretical analysis of conduction-cooled current lead for superconducting magnet

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