Modelling V-I Measurements of Nb3Sn Accelerator Magnets with Conductor Degradation

Ruben Keijzer, Giovanni Succi, Gerard Willering, Bernardo Bordini, Luca Bottura, Franco Mangiarotti, Marc Dhalle, Herman Ten Kate

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Abstract

In the framework of the High-Luminosity Large Hadron Collider (HL-LHC) project, 11 T dipole and MQXF quadrupole magnets employing Nb3Sn technology have been tested in short and long test configurations. Nb3Sn magnets are more sensitive than Nb-Ti magnets to a potential degradation of their conductors during production, testing, and cycling operation. At CERN, new diagnostic tools and measurement procedures have been developed to investigate, in detail, the performance of Nb3Sn accelerator type magnets. This is accomplished by V-I measurements extracted from voltage taps on conductor sections as well as entire coils. A leading hypothesis for the cause of decaying voltages on current plateaus of the V-I measurements is the presence of an inhomogeneous defect in the Rutherford cable. Current redistribution for bypassing such defects takes place through a current diffusion process, which leads to a decaying voltage over the affected cable sections. Using the simulation software THEA, the general behavior of this phenomenon has been studied. Good qualitative agreement is found between simulation and magnet test results.

Original languageEnglish
Article number4001105
JournalIEEE transactions on applied superconductivity
Volume32
Issue number6
Early online date24 Feb 2022
DOIs
Publication statusPublished - Sep 2022

Keywords

  • Coils
  • continuum model
  • Current measurement
  • Degradation
  • Nb3Sn
  • Nonhomogeneous media
  • Rutherford cables
  • superconducting accelerator magnets
  • Superconducting magnets
  • Voltage
  • Voltage measurement
  • 22/1 OA procedure

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