Development of 3kA conduction cooled HTS current lead system

In superconducting magnet systems the current leads are usually divided into two parts. Normal metal like brass or copper is often used in the first part from the room temperature to the temperature of the radiation shield. The second part down to the magnet is made of high temperature superconductors (HTS). HTS leads can reduce the conductive heat load because they have poor thermal conductivity. Since HTS wires are lossless with direct current and have fair tolerance to the magnetic field only Ohmic losses are generated in the contact resistances at the current terminals. Thus, efficient current leads require that appropriate solders are used to reduce the contact resistances. In this paper, the thermal and contact resistances as well as thermal conduction losses of Bi-2223/Ag current leads are experimentally investigated using indium-and tin-based solders at operation temperatures between 20 and 77 K. Finally, the measured data is utilized to design an efficient HTS current lead to the current range of 0-1000 A.

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“…2. Thermal conductances were calculated using classical steady state method (6) where in the mean temperature of the joint [8]. Fig.…”

Section: Thermal Contact Conductancesmentioning

confidence: 99%

“…When the HTS bulk is used the heat load can be four times smaller compared to the HTS tapes [5]. However, then there can be problems with electrical and mechanical stability [6]. Thus, HTS tapes with a high conductivity matrix offer good compromise between stability and thermal conduction.…”

Section: Introductionmentioning

confidence: 99%

Measured Performance of Different Solders in Bi2223/Ag Current Leads

Hiltunen

Korpela

Laine

et al. 2008

IEEE Trans. Appl. Supercond.

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“…Foil heaters were also installed at the midplane (between DP#2 and DP#3). Two-stage cryocoolers for the HTS current leads and another cryocooler for the thermal shield were also installed in the vacuum vessel [5]. The experimental coil was able to be cooled below 4.6 K without loads.…”

Section: Thermal Runaway Testmentioning

confidence: 99%

Excitation Tests of Prototype HTS Coil With Bi2212 Cables for Development of High Energy Density SMES

Tosaka

Koyanagi

Ohsemochi

et al. 2007

IEEE Trans. Appl. Supercond.

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Development of the SMES using high temperature superconducting (HTS) coil has progressed as a Japanese national project since FY 2004. The objective of the project is to obtain around twice the normal energy density via an HTS-LTS "hybrid" coil system compared to an LTS coil system. The HTS coil is composed of sixteen double-pancake coils and the double-pancake coil is wound with a Bi2212 Rutherford-type cable. The HTS coil is operated at 4.2 K in liquid helium bath with the LTS coil, and operated at maximum field of 8.9 T. Before we made a hybrid coil system, we verified the design issues using HTS experimental coils. In this paper mechanical compression tests, DC operation tests and thermal runaway tests using the experimental coils are discussed.

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