Cryogenic Test of High Temperature Superconducting Current Leads at ENEA

Abstract

The LHC (Large Hadron Collider), the accelerator being constructed on the CERN site, involves the operation of more than 8000 superconducting magnets of various current ratings. Essential elements for the powering of these magnets are the HTS current leads. These devices provide the electrical link between the warm cables from/to the power converter and the low temperature superconducting bus bars bringing the current from/to the cryo-magnets. Thus they operate in a temperature range between room temperature and liquid helium temperature. The operation of the LHC will require more than 1000 HTS current leads operating at currents ranging from 600 A to 13000 A. Cryogenic tests of the series of 13000 A and 6000 A HTS current leads are made at ENEA in the framework of a CERN-ENEA collaboration. This report gives an overview of the experimental set-up built in ENEA. The set-up was designed following the typical criterion of a scientific experiment but it was dimensioned to satisfy the schedule of an industrial scale activity, having in mind the large number of components to be tested in a period of less than two years. The related data acquisition system is also described, together with the results of the tests on the current leads. ABSTRACTThe LHC (Large Hadron Collider), the accelerator being constructed on the CERN site, involves the operation of more than 8000 superconducting magnets of various current ratings. Essential elements for the powering of these magnets are the HTS current leads. These devices provide the electrical link between the warm cables from/to the power converter and the low temperature superconducting bus bars bringing the current from/to the cryo-magnets. Thus they operate in a temperature range between room temperature and liquid helium temperature. The operation of the LHC will require more than 1000 HTS current leads operating at currents ranging from 600A to 13000A. Cryogenic tests of the series of 13000A and 6000A HTS current leads are made at ENEA in the framework of a CERN-ENEA collaboration.This report gives an overview of the experimental set-up built in ENEA. The set-up was designed following the typical criterion of a scientific experiment but it was dimensioned to satisfy the schedule of an industrial scale activity, having in mind the large number of components to be tested in a period of less than two years. The related data acquisition system is also described, together with the results of the tests on the current leads.

Operational experience and consolidations for the current lead control valves of the large hadron collider

“…The main operational conditions common to all valves are listed in TABLE 3 [5], the sizes of the valves are listed in TABLE 2. One of the main requirements is the fact that the valves are used to control the temperature of the leads with a closed loop regulation.…”

“…TABLE 1 lists the types and the number of current leads found in the LHC [3,4,5]. The flow of helium through the leads is regulated by room temperature control valves installed in the vicinity of the current leads.…”

Design, Production and First Commissioning Results of the Electrical Feedboxes of the LHC

“…More than 1000 HTS leads are installed in the DFBs (see TABLE 2), making the LHC the world's largest user of HTS leads. More details concerning the development, performance and validation of the HTS leads can be found in [3][4][5]. The 120 A current leads are conduction cooled, with 3 gas cooled stages of heat intercept [6].…”

“…The 6 kA and 13 kA leads are installed individually on the DFBs, the 600 A are mounted in assemblies of four on a common flange and the 120 A are installed in assemblies of 4 or 8 on a common flange. The 13 kA, 6 kA and 600 A use a High Temperature Superconductor (HTS) bottom part to limit the heat loads to the cryogenic system [3][4][5]. The bottom end of the HTS is connected to the Nb-Ti based busbars at 4.5 K while the top part is kept at 50 K by a flow of 20 K helium that also cools the top part of the leads made of a copper heat exchanger.…”

“…The current is brought to the DFBs by copper cables and is transferred to superconducting busbars at 4.5 K by 4 types of current leads, designated by their current ratings: 13 kA, 6 kA, 600 A, and 120A [3][4][5][6]. The 6 kA and 13 kA leads are installed individually on the DFBs, the 600 A are mounted in assemblies of four on a common flange and the 120 A are installed in assemblies of 4 or 8 on a common flange.…”