Superconducting current-leads made from high Tc superconductor and normal metal conductor

Mumford, F.J.

doi:10.1016/0011-2275(89)90086-6

Cited by 39 publications

(4 citation statements)

References 1 publication

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“…Now, using a different parameterization, let us project the solution on the (j, Θ L ) plane along a curve with constant u, as presented in Figure 8. The bifurcation curves have an "S" form exhibiting two limit points determined by the roots of the equation dj/dΘ L u = 0 (27) as they separate the stable from the unstable solutions. The lower stable solutions correspond to the superconducting branch, whereas the upper ones correspond to the normal branch.…”

Section: Resultsmentioning

confidence: 99%

Analysis of High-Temperature Superconducting Current Leads: Multiple Solutions, Thermal Runaway, and Protection

Krikkis¹

2023

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The multiple steady states of Ag/Bi2212-composite high-Tc superconducting leads modeling current delivery to a superconducting magnet have been numerically calculated. The model is based on longitudinal conduction combined with convective heat dissipation from a helium gas stream along the conductor. Because of the nonlinearities introduced by the voltage–current relationship and the temperature-dependent material properties, up to three solutions have been identified within the range of parameters considered. Linear stability analysis reveals that two of them are stable, i.e., the superconducting and the normal branches, while the remaining one is unstable. The limit points separating the stable from the unstable steady states form the blow-up threshold, beyond which any further increase in the operating current results in a thermal runway. Interesting findings are that for low filling ratios no bounded solution exists when the length of the lead exceeds the lower limit point, while very high maximum temperatures may be encountered along the normal solution branch. The effect of various parameters such as the conduction–convection parameter, the applied current, and the reduction in coolant flow (LOFA) on the bifurcation structure and their stabilization effect on the blow-up threshold are also evaluated. Apart from the steady and unsteady operating modes, the multiplicity analysis is also used to identify the range of the design and operating variables where safe operation, with a sufficient margin from the onset of instabilities, may beestablished, thus facilitating the protection of the leads and the device connected to it.

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Section: Resultsmentioning

confidence: 99%

Analysis of High-Temperature Superconducting Current Leads: Multiple Solutions, Thermal Runaway, and Protection

Krikkis¹

2023

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“…The next significant progression in the CL development took place in the late 1980s after the discovery of HTS above the boiling temperature of liquid nitrogen (LN 2 ) in 1986. Shortly afterwards, in 1989, HTS applications into CLs as a lowtemperature (or second) stage took off as a field of study and the advantages were analysed by shorting out metallic conductor and eliminating Joule heat generation at cold ends [11,12], which opened up the possibility of a lower heat leak beyond the limitation of the WFL law. 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.…”

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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“…Since high-temperature superconductors (HTSs) generate zero Joule loss under the superconducting state and have lower thermal conductivity than normal metals [1], they become an ideal material for current leads [2]. 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].…”

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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Superconducting current-leads made from high Tc superconductor and normal metal conductor

Cited by 39 publications

References 1 publication

Analysis of High-Temperature Superconducting Current Leads: Multiple Solutions, Thermal Runaway, and Protection

Analysis of High-Temperature Superconducting Current Leads: Multiple Solutions, Thermal Runaway, and Protection

Theoretical analysis of conduction-cooled current lead for superconducting magnet

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

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