Conceptual design of a forced-flow-cooled 20-kA current lead using Ag-alloy-sheathed Bi-2223 high-temperature superconductors

Abstract

The use of high-temperature superconductors in current leads lo reduce refrigeration power has been investigated by many groups in the past. Most used YBCO and Bi-2212 bulk superconductors, although their critical current density is not very high. In this paper, Bi-2223 HTSC tapes sheathed with Ag alloys are used in the design of a 20-kA current lead because of their higher critical current in medium magnetic fields. The lead current of 20 kA is related to the coil current of the planned stellarator WENDELSTEIN 7-X. Forced-flow helium cooling has been used in the design, allowing position-independent and well-controlled operation. The design characteristics of the lead are presented and 4-K helium cooling of the whole lead, as well as 60-K helium cooling of the copper part of the lead, is discussed. The power consumption at zero current, and the lead's behaviour in case of loss of coolant flow, are given. The results of the design allow extrapolation to current leads of the 50-kA range. Konzeptioneller

Modelling of the test of the JT-60SA HTS current leads

“…Current leads are devices adopted to connect a power supply, typically at room temperature, to various clients, usually at cold (cryogenic) temperatures. High temperature superconducting current leads (HTS-CL) cooled by He gas have been designed since more than 20 years [1] and used for supplying the electrical current to superconducting magnets in both fusion devices [2], [3] and particle accelerators [4]. Other concepts have been developed in the past, like the so-called conventional CLs, which are not equipped with a superconductor, leading to various pros and cons with respect to the binary (HTS) CLs which are discussed in detail e.g.…”