TD-13-00x

SC Accelerator Magnet Program

G. Apollinari, A.V. Zlobin

02/25/2013

  1. Overview and Long-term strategy

The mission of the SC Accelerator Magnet Program (High Field Magnet Program) at Fermilab is the development of advanced SC magnets and baseline technologies for present and future particle accelerators. This program secures and expands Fermilab’s technical capabilities and leadership role in accelerator based HEP research. This activity is assured to have a strong impact on the future Energy Frontier HEP programs in the U.S. and worldwide, including luminosity and energy upgrades for the LHC as well as the construction of new machines such as the Muon Collider or new Hadron Collider. In ten years the program has to provide technical capabilities and a leadership position for Fermilab to participate in focused R&D and then in construction of the next HEP accelerator complex anticipated in the next decade or two.

During the past decade the program focused on the development of high-field accelerator magnets with operating fields up to 15 T based on Nb3Sn superconductor. In the long term, the program scope will include the development of accelerator magnets with operating fields up to 20-25 T. This program also supports the development of new SC strands and cables suitable for use in high-field accelerator magnets, improvements of magnet design and analysis methods and tools, fabrication and test infrastructure, instrumentation, and training of young magnet scientists and engineers at Fermilab.

The first step towards the long-term goals will be the successful development and demonstration of Nb3Sn accelerator magnets based on the collar technology which is the technology of choice for long magnet strings and one in which Fermilab maintains unique expertise on the National scene. It is expected that this technology will find immediate use in real machines, in particular for the LHC luminosity upgrades planned for 2017-2021. The decision on the use of Nb3Sn accelerator magnets in the LHC upgrades is expected around 2015 and will be made by CERN based on the results of development and testing of 5.5 m long twin-aperture 11 T dipole prototypes for LHC collimation system upgrade by a FNAL-CERN collaboration and 4 m long large-aperture high-gradient quadrupole demonstrator for new high-luminosity IRs by US-LARPand CERN.

Fermilab is a key member of the LARP collaboration which has been working on the Nb3Sn IR quadrupoles for the LHC luminosity upgrade since 2003. The present LARP Magnet program strategy to develop and demonstrate 150 mm aperture Nb3Sn IR quadrupoles for the new LHC IRs is described elsewhere. To demonstrate the feasibility of Nb3Sn dipoles for the LHC collimation system upgrade, Fermilab in collaboration with CERN has started in FY2011 a joint R&D program with the goal of building by the end of 2015 a 5.5-m long twin-aperture Nb3Sn dipole prototype suitable for the LHC collimation system upgrade. These magnets can be also used to provide space in the LHC lattice for different insertion devices such as dynamic collimators based on the e-lens concept, corrector magnets, BPMs, etc. In the future, these magnets or their modificationscould be considered as a baseline design for a new hadron collider.

  1. FY13-FY16Goals and Plan

The Fermilab’s role and tasks in the new LARP Magnet program are described elsewhere.To reach the long-term goals mentioned above, in the next 4 years FNAL HFM program has to accomplish the three phases of the11 T dipole R&D and prepare to the participation in dipole collared coil production:

  • The first (essentially complete) phase of the HFM program is the design and construction of a single-aperture 2 m long demonstrator dipole, delivering 11 T at the nominal LHC current of 11.85 kA and temperature of 1.9 K in a 60 mm bore with 20% margin (FY11-12).
  • The second phase of the program includes the fabrication and test of two 2 m long, twin-aperture demonstrator dipoles to confirm the final magnet design, demonstrate the magnet performance parameters and their reproducibility (FY13-14).
  • And finally, the third phase of the program will focus on the design and technology scale up byfabricating and testinga 5.5 m long twin-aperture dipole prototype (FY14-15).

This program also will optimize and demonstrate the Nb3Sn strands and cables as well as radiation hard insulation suitable for use in the LHC 11 T dipoles (FY13-FY15).

In addition, we will invest a minimal effort to continue the collaboration with KEK and NIMS in Japan started several years ago on the development of accelerator magnet technology based on Nb3Al strands and cables.

The program promotes improvement of Fermilab’s magnet infrastructure to support the previously described R&D activities and possible participation in magnet production (in the case of a successful demonstration and selection of these magnets for the LHC collimation system upgrade, a joint FNAL-CERN project to fabricate eight or more 11 T 11 m long dipoles will be proposed). The infrastructure improvements in support of 11 T dipole program include the modernization of 7 m long SELVA winder (FY12-13) and installation of a second 7 m long press for long coils curing and collaring (FY13). To support the LARP Magnet R&D Fermilab will upgrade the VMTF (Vertical Magnet Test Facility) to test magnets with operating currents up to 30 kA in superfluid helium (FY13-14) and the horizontal test facility to test Nb3Sn dipoles and quadrupoles with currents up to 20 kA at 1.9 K (FY14-15). These improvements will also be used later in magnet R&D for MC and LHC energy upgrades.

2.1FY13 Plan and Expected Outcomes

After fabrication and test of the first 2 m long single-aperture demonstrator dipole in June of FY12, in FY13 Fermilab will continue optimization of the strand, cable and insulation for the 11 T dipole based on Nb3Sn technology for LHC upgrades and start the development of the 1 m and 2 m long twin-aperture 11 T dipole models. To improve the quench performance and demonstrate its reproducibility four 1 m long dipole coils with RRP-150/169 and RRP-108/127 strands, 40-strand cored Nb3Sn cable and optimized fabrication process will be fabricated and collared. These two collared coils will be used in the first 1 m long twin-aperture Nb3Sn dipole model to be built and tested at Fermilab in 2013. Prior to the assembly of the twin-aperture magnet each collared coil will be tested in a single-aperture configuration and a short twin-aperture mechanical model will be assembled and tested.

Based on this result we will finalize the design, parameters and fabrication process of the collared coils for the first twin aperture 2 m long 11 T dipole demonstrator. Fermilab will start fabrication offour 2 m long coils for the twin-aperture 2 m long dipole demonstrator magnet to be assembled and tested at CERN in 2014.

We will also continue the study of radiation resistant materials to replace epoxy for Nb3Sn coil impregnation by a) assembling and testing a 1 m long 90 mm quadrupole coil impregnated with MATRIMID in a coil test structure (quadrupole mirror); and b) impregnating a 2 m long dipole coil with MATRIMID.

Fermilab will continue the optimization of the 40-strand cable with stainless steel core and advanced Nb3Sn strand and its qualification for use in production of the 11 T dipoles by testing magnets with RRP-108/127 and RRP-150/169 strands.

Collaboration with KEK and NIMS in Japan on the development of accelerator magnets based on Nb3Al strands and cableswill continue. In the framework of this collaboration cable short samples will be produced and tested at Fermilab based on Nb3Al strand provided by NIMS and KEK.

Conceptual designs of the large-aperture (up to 500 mm) high-field IR quadrupoles for Higgs Factory based on Nb3Sn technology will be developed and analyzed in support of MAP.

The long-term plans for 20-25 T magnet R&D based on hybrid LTS/HTS coils will be further shaped and optimized taking into account the available resources and program priorities.

2.2 FY14 Plan and Expected Outcomes

In FY14 Fermilab will continue focusing on the development and demonstration of the 11 T dipole based on Nb3Sn technology for LHC upgrades. We will finish assembly and test of a twin-aperture 1 m long 11 T dipole model at Fermilab. Based on this result we will finalize the fabrication process and performance parameters of the collared coils for the first twin aperture 2 m long 11 T dipole demonstrator. Fermilab will finish fabrication of four 2 m long coils for the twin-aperture 2 m long dipole demonstrator magnet. Wewill assemble and test two 2 m long 11 T dipole collared for the first twin-aperture 2 m long dipole demonstrator magnet to be assembled and tested at CERN in 2014.

We will procure tooling and start scale up of the 11 T coil length from 2 m to 5.5 m. Two 5.5 m long practice coils (one with Cu cable and one with Nb3Sn cable) will be fabricated. The Nb3Sn long coil will be tested in a long coil test structure (dipole mirror) at Fermilab or CERN in FY15.

Fermilab will continue the study of radiation resistant materials to replace epoxy for Nb3Sn coil impregnation by impregnating with MATRIMID a 5.5 m long dipole coil.

Fermilab will continue the optimization and scale up of 40-strand cable up to 650 mlong with stainless steel core, advanced Nb3Sn strand and its qualification for use in production of the 11 T dipoles.

Collaboration with KEK and NIMS in Japan on the development and demonstration of accelerator magnets based on Nb3Al cables will continue. A 50 m long unit length of 27-strand cable using 0.7 mm Nb3Al strand produced in Japan will be fabricated at Fermilab and short samples will be tested.

Conceptual design of the high-field large-aperture IR quadrupoleand Storage Ring dipole magnets for Higgs Factory based on Nb3Sn technology will continue in support of MAP.

The long-term plans for 20-25 T magnet R&D based on hybrid LTS/HTS coils will be further worked out taking into account the available resources, program priorities and results of the HTS conductor development programs.

2.3 FY15-16 Plan and Expected Outcomes

In FY15-16 Fermilab will fabricate two 5.5 m long dipoles coils which will be collared for use in the 5.5 m long twin-aperture dipole prototype for LHC upgrades. Prototype assembly and test will be done at CERN in FY15-16. Additional tests of single- or twin-aperture short dipole models could be conducted to finalizethe production magnet design and performance specifications. Based on the results of these tests and collimation system studies at CERN the decision on the collimation system upgrade and Nb3Sn magnet production plans will be taken.

Collaboration with KEK and NIMS in Japan on the development and demonstration of accelerator magnets based on Nb3Al cables will continue. Short quadrupole coil will be fabricated and tested in a quadrupole coil test structure (quadrupole mirror) at various pre-stress levels. This work will demonstrate the Nb3Al technology for application in accelerator magnets with high Lorentz force level.

Conceptual design studies of the high-field large-aperture SC magnets for MC SR&IR based on Nb3Sn and other technologies will continue in support of MAP. Proposal for the MC Magnet model R&D will be prepared.

In FY15-16 the conceptual design work on a HTS insert will start with the goal to beginthe engineering design and insert fabrication in FY17 and beyond.

  1. FY13-FY16 Metrics and Milestones

FY13:

  • Assemble and test 90-mm TQ coil impregnated with MATRIMID in quadrupole test structure by 12/2012
  • Fabricate two coils and test the 1 m long single-aperture 11 T dipole model based on RRP-150/169 strand and cored cable by 03/2013
  • Impregnate 2 m long dipole coil MBHSP04 with MATRIMID and inspect impregnation quality by 04/2013
  • Fabricate 4 UL (~850 m) of the 40-strand cable with stainless steel core and RRP-108/127 strand by 05/2013
  • Assemble and test twin-aperture dipole mechanical model by 06/2013
  • Fabricate two coils and test the 1 m long single-aperture 11 T dipole model based on RRP-108/127 strand and cored cable by 09/2013
  • Test ~35 strand samples extracted from Nb3Sn and Nb3Alcables by 09/2013

FY14:

  • Complete fabrication of four2 m long coils for the first twin-aperture dipole demonstrator by 11/2013
  • Fabricate and test the first 2 m long collared coil for the first twin-aperture dipole demonstrators by 12/2013
  • Fabricate and test the second 2 m long collared coil for the first twin-aperture dipole demonstrators by 03/2014
  • Fabricate 600 m long unit length of the 40-strand cable for 5.5 m long practice coil by 05/2014
  • Fabricate 50 m long unit length of Nb3Al cable by 06/2014
  • Procure long tooling and fabricate the first 5.5 m long practice coil by 09/2014
  • Test 15 witness samples extracted from Nb3Sn and Nb3Al cables by 09/2014

FY15:

  • Fabricate two 600 m long ULs of the 40-strand cable for 5.5 m long coils by 10/2014
  • Test 5.5 m long dipole coil in a long coil test structure by 01/2015
  • Fabricate two 5.5 m long coils and assemble collared coil for the 11 T dipole prototype by 04/2015
  • Fabricate and test a short quadrupole coil based on Nb3Al cable in a mirror configuration by 06/2015
  • Test 15 strand samples extracted from 40-strand cored cable by 09/2015
  1. Risks to the FY13 Plan

FY13 Goal or Milestone / Threats / Risk Priority (H, M, L)a / Mitigation Actions / Owner
Fabricate coils and test the 1 m long single-aperture 11 T dipole model based on RRP-150/169 strand and cored cable / Coil damage during fabrication and assembly / H / a)Prepare and test coil witness samples
b)Measure coil size and control pre-stress during assembly using strain gauges
Fabricate coils and test the 1 m long single-aperture 11 T dipole model based on RRP-108/127 strand and cored cable / Coil damage during fabrication and assembly / H / c)Prepare and test coil witness samples
d)Measure coil size and control pre-stress during assembly using strain gauges
Fabricate 4 UL of the 40-strand cable with stainless steel core and RRP-108/127 strand / Strand cross-overs, cable geometry out of tolerance, large strand degradation / H / a)make initial run of cable using Cu strand and inspect for cross-overs
b)control cable width and mid-thickness during fabrication
c)test extracted strand samples prior cable fabrication
Teststrand short samples extracted from Nb3Sn and Nb3Al cables / Sample loss during processing or testing / L / Make and test more samples
aRisk Priority (HML) H=high; M=medium; L=low