HTS Current Leads: Performance Overview in Different Operating Modes

Abstract

Abstract-High Temperature Superconducting (HTS) current leads have become, in the last few years, a valid choice for the powering of superconducting magnet systems. After the construction and test of more than a thousand of HTS leads for the Large Hadron Collider, with a consequent improved confidence in the long-term and large scale operation of these devices, it is being envisaged to equip several other large superconducting magnet systems with this type of lead. The approach used in the optimization and design of such leads must take into account the requirements of the electrical and cryogenic systems as well as the local environment. The paper summarizes the results of the analysis made on HTS current leads, with special attention to the optimization process to be followed in different scenarios that include both DC and pulsed operation. Case studies are also presented and discussed. The calculation of the optimum performance in the various operating conditions was made assuming a lead design of the type used for LHC.

Extending the Use of HTS to Feeders in Superconducting Magnet Systems

“…This is a strong motivation to remove "active" parts of the electrical feedboxes away from the beam, to places where they can be shielded. 2) HTS leads have lower heat losses than conventional leads [3]. Higher currents can therefore be envisaged in the magnets, reducing the inductance and thus easing the problem of quench protection.…”

“…Conventional feedbox cryostats can be displaced within the accelerator tunnel, or removed from it to be placed in existing alcoves, parallel tunnels or underground halls. The resistive part of the leads, joined at their cold ends to the HTS bus-bars, can be installed in a relatively radiation-free, more accessible location, and optimized for operating with the cold end at a convenient temperature [3]. The advantages include removing sensitive elements (valves, electronics, heating control, etc.)…”

Evaluation of turbo-Brayton cycle for cooling current leads: Integrated current lead/heat exchanger

“…Current leads (CL) to cryogenic environment introduce substantial heat loads [1,2,3]. When the leads are designed to carry substantial current and the cryostat is small (as in the case of electric power distribution systems), the cryogenic load is dominated by the CLs.…”

“…Thus, there has been substantial effort in optimizing conduction-cooled CLs, especially for operation at low (~4 K) temperatures. [1][2][3].…”

“…A substantial fraction of the power dissipated in the upper, hotter regions of the CL can be intercepted at this intermediate temperature. A substantial effort has been devoted to optimizing hybrid CL's, where the lower stage uses high-temperature superconductors (HTS) [2] We have extended McFee's calculation to the case when the cryogenic temperature is around liquid nitrogen [4]. In this case, there are advantages of using two stages, with an intermediate station at ~ 150 K, with both stages independently optimized.…”