Dimensional Changes of Nb 3 Sn Rutherford Cables During Heat Treatment

Abstract-The U.S. LHC Accelerator Research Program, in close collaboration with CERN, has developed three generations of high-gradient quadrupole (HQ) Nb3Sn model magnets, to support the development of the 150 mm aperture Nb3Sn 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. The HQ03 magnet was tested 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. To study the capability of correcting the low-order non-allowed field errors, magnetic shims were installed in HQ03. 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. Finally, we compare the field errors due to the inter-strand coupling currents between HQ03 and HQ02.Index Terms-LARP, Nb3Sn quadrupole magnets, field quality.

Section: B Coil Positioning Tolerancesupporting

confidence: 78%

Analysis of Field Errors for LARP Nb$_3$ Sn HQ03 Quadrupole Magnet

Wang

Ambrosio

Chlachidze

et al. 2017

“…Free simply means that the cable is free to expand without any constraint by tooling or insulation. †Measured expansion from coil cross section analysis [25], [26]. ‡Measured expansion from LBNL cable experiments [27].…”

Section: B Cable Expansionmentioning

confidence: 99%

“…This process is slow but is not subject to scaling uncertainties. A cross section of LARP coil 1 was analyzed with an optical comparator and a cross section of CERN coil 101 was analyzed with image post processing [25], [26].…”

Section: Coil Cross Section Analysismentioning

confidence: 99%

Fabrication and Analysis of 150 mm Aperture Nb3Sn LARP MQXF Coils

Holik

Ferracin

Krave

et al. 2016

Self Cite

Abstract-The US LHC Accelerator Research Program (LARP)and CERN are combining efforts for the HiLumi-LHC upgrade to design and fabricate 150 mm aperture, interaction region quadrupoles with a nominal gradient of 130 T/m using Nb3Sn. To successfully produce the necessary long MQXF triplets, the HiLumi-LHC collaboration is systematically reducing risk and design modification by heavily relying upon the experience gained from the successful 120 mm aperture LARP HQ program. First generation MQXF short (MQXFS) coils were predominately a scaling up of the HQ quadrupole design allowing comparable cable expansion during Nb3Sn formation heat treatment and increased insulation fraction for electrical robustness. A total of 13 first generation MQXFS coils were fabricated between LARP and CERN. Systematic differences in coil size, coil alignment symmetry, and coil length contraction during heat treatment are observed and likely due to slight variances in tooling and insulation/cable systems. Analysis of coil cross sections indicate that field-shaping wedges and adjacent coil turns are systematically displaced from the nominal location and the cable is expanding less than nominally designed. A second generation MQXF coil design seeks to correct the expansion and displacement discrepancies by increasing insulation and adding adjustable shims at the coil pole and midplanes to correct allowed magnetic field harmonics.

“…The angle was reduced from the "first-generation" value of 0.55° to bring the critical current degradation due to cabling to <5% in the PIT conductor and <3% in the RRP conductor. For the coil design and the field quality computation, an increase of width and midthickness of 1.2% and 4.5% respectively was assumed, with the same keystone angle, as observed by dimensional measurements performed on cross-section of first-generation coils [16]. The cable is insulated with braided S2-glass, with a nominal thickness of 145 µm +-5 at a pressure of 5 MPa.…”

Section: Superconducting Strand and Cablementioning

confidence: 99%

“…140 mm long end-shoe extensions at the lead ends of both layers protect the area where the Nb-Ti to Nb3Sn splices are made. For the short model program, 13 first-generation coils have been fabricated, including a coil wound with Cu cable, and 2 practice coils, which were cut to analyze the quality of impregnation and the conductor positions [16]. LARP coil 02 was tested as a single coil in a "mirror magnet" structure and reached 90% of the maximum current limit.…”

Section: Superconducting Strand and Cablementioning

confidence: 99%

Development of MQXF: The Nb3Sn Low-<inline-formula> <tex-math notation="LaTeX">$\beta$</tex-math></inline-formula> Quadrupole for the HiLumi LHC

Ferracin

Ambrosio

Anerella

et al. 2016

Self Cite

Abstract-The HiLumi LHC project has as the main objective to increase the LHC peak luminosity by a factor five and the integrated luminosity by a factor ten. This goal will be achieved mainly with a new Interaction Regions lay-out, which will allow a stronger focusing of the colliding beams. The target will be to reduce the beam size in the Interaction Points by a factor of two, which requires doubling the aperture of the low-β (or inner triplet) quadrupole magnets. The use of Nb3Sn superconducting material and, as a result, the possibility of operating at magnetic field levels in the windings higher than 11 T, will limit the increase in length of these quadrupoles, called MQXF, to acceptable levels. After the initial design phase, where the key parameters were chosen and the magnet's conceptual design finalized, the MQXF project, a joint effort between the US LHC Accelerator Research Program (LARP) and CERN, has now entered construction and test phase of the short models. Concurrently, the preparation for the development of the full length prototypes has been initiated. This paper will provide an overview of the project status, describing and reporting on the performance of the superconducting material, the lessons learnt during the fabrication of superconducting coils and support structure, and the fine tuning of the magnet design in view of the start of the prototyping phase.