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Title: Analysis of field errors for LARP Nb 3Sn HQ03 quadrupole magnet

The U.S. LHC Accelerator Research Program, in close collaboration with CERN, has developed three generations of high-gradient quadrupole (HQ) Nb 3Sn model magnets, to support the development of the 150 mm aperture Nb 3Sn quadrupole magnets for the High-Luminosity LHC. The latest generation, HQ03, featured coils with better uniformity of coil dimensions and properties than the earlier generations. We tested the HQ03 magnet at FNAL, including the field quality study. The profiles of low-order harmonics along the magnet aperture observed at 15 kA, 1.9 K can be traced back to the assembled coil pack before the magnet assembly. Based on the measured harmonics in the magnet center region, the coil block positioning tolerance was analyzed and compared with earlier HQ01 and HQ02 magnets to correlate with coil and magnet fabrication. Our study the capability of correcting the low-order non-allowed field errors, magnetic shims were installed in HQ03. Furthermore, the expected shim contribution agreed well with the calculation. For the persistent-current effect, the measured a4 can be related to 4% higher in the strand magnetization of one coil with respect to the other three coils. Lastly, we compare the field errors due to the inter-strand coupling currents between HQ03 and HQ02.
Authors:
ORCiD logo [1] ;  [2] ;  [2] ;  [2] ;  [3] ;  [2] ;  [1] ;  [1] ;  [2]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Report Number(s):
FERMILAB-PUB-16-564-TD
Journal ID: ISSN 1051-8223; 1501407
Grant/Contract Number:
AC02-07CH11359
Type:
Accepted Manuscript
Journal Name:
IEEE Transactions on Applied Superconductivity
Additional Journal Information:
Journal Name: IEEE Transactions on Applied Superconductivity; Journal ID: ISSN 1051-8223
Publisher:
Institute of Electrical and Electronics Engineers (IEEE)
Research Org:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; LARP; Nb3Sn quadrupole magnets; field quality
OSTI Identifier:
1336408