A future circular collider (FCC) with a center-of-mass energy of 100 TeV and a circumference of around 100 km, or an energy upgrade of the LHC (HE-LHC) to 27 TeV require bending magnets providing 16 T in a 50-mm aperture. Several development programs for these magnets, based on Nb3Sn technology, are being pursued in Europe and in the U.S. In these programs, cos–theta, block-type, common-coil, and canted–cos–theta magnets are explored; first model magnets are under manufacture; limits on conductor stress levels are studied; and a conductor with enhanced characteristics is developed. This paper summarizes and discusses the status, plans, and preliminary results of these programs.

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The 16 T Dipole Development Program for FCC and HE-LHC

The high-luminosity upgrade of the Large Hadron Collider (HL-LHC) requires new high field and large-aperture quadrupole magnets for the low-beta inner triplets (MQXF). With a nominal operating gradient of 132.2 T/m in a 150 mm aperture and a conductor peak field of 11.3 T, the new quadrupole magnets are based on Nb3Sn superconducting technology. After a series of short models constructed in close collaboration by LARP (LHC Accelerator Research Program) and CERN, the development program is entering in the series production phase with CERN on one side and the US Accelerator Upgrade Project (US-AUP) on the other side assembling and testing full-length magnets. This paper describes the status of the development activities at CERN, in particular on the cold powering test of the first MQFXB prototype and on the construction of the second full scale prototype. Critical operations such as reaction heat treatment, coil impregnation and magnet assembly are discussed. Finally, the plan towards the series production is described.

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Progress in the Development of the Nb 3 Sn MQXFB Quadrupole for the HiLumi Upgrade of the LHC

With the successful test of the first two pre-series magnets the US HL-LHC Accelerator Upgrade Project has started production of the MQXFA magnets to be used in Q1/Q3 inner triplet elements of the HL-LHC. This good start comes after the test of two prototypes with limited performance, and it demonstrates the importance of learning from past issues. Therefore, in this paper we want to share the most important lessons learned so far, focusing on those which may be more interesting for similar projects. We will also present the status of MQXFA fabrication in the US.

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Lessons Learned From the Prototypes of the MQXFA Low-Beta Quadrupoles for HL-LHC and Status of Production in the US

Preliminary design and evaluation of large‐diameter superconducting cable toward GW‐class hybrid energy transfer of electricity, liquefied natural gas, and liquefied nitrogen

The High-Luminosity project (HL-LHC) of the CERN Large Hadron Collider (LHC), requires low <inline-formula><tex-math notation="LaTeX">$\beta$</tex-math></inline-formula>* quadrupole magnets in Nb <inline-formula><tex-math notation="LaTeX">$_\text{3}$</tex-math></inline-formula>Sn technology that will be installed on each side of the ATLAS and CMS experiments. After a successful short-model magnet manufacture and test campaign, the project has advanced with the production, assembly, and test of full-size 7.15-m-long magnets. In the last two years, two CERN-built prototypes (MQXFBP1 and MQXFBP2) have been tested and magnetically measured at the CERN SM18 test facility. These are the longest accelerator magnets based on Nb <inline-formula><tex-math notation="LaTeX">$_\text{3}$</tex-math></inline-formula>Sn technology built and tested to date. In this paper, we present the test and analysis results of these two magnets, with emphasis on quenches and training, voltage-current measurements and the quench localization with voltage taps and a new quench antenna.

Power Test of the First Two HL-LHC Insertion Quadrupole Magnets Built at CERN

In the framework of the development of high field magnets made of Nb3Sn superconductor for projects such as high luminosity upgrade of the large hadron collider and future circular collider studies, it is needed to refine the understanding of the coil winding process and its impact on the overall mechanical behavior of the conductor. For this purpose, a new cable winding setup has been developed in order to compare the windability of different Nb3 Sn Rutherford cables. In addition, various geometrical cable inspection methods were tested and compared. First experimental results obtained with the new set-up for winding tests are summarized.

Testing Mechanical Behavior of Nb3Sn Rutherford Cable During Coil Winding

In the framework of the development of high field magnets made of Nb3Sn superconductors for projects like the high luminosity upgrade of the large hadron collider (HL-LHC) and FCC studies, it is necessary to refine the understanding of the winding process and its impact of the overall mechanical integrity of the conductor The mechanical behavior during winding of the unreacted Rutherford-type Nb3Sn cables has been studied experimentally In order to quantify the windability of the various cable designs, the measurement method and a dedicated specimen-scanning device has been developed The validation of the device and achieved repeatability are presented in this paper The results from the first winding test campaign with cables 11 T dipole RRP, 11 T dipole dummy Cu, MQXF, FRESCA 2, and NbTi are shown

Windability Tests of Nb 3 Sn Rutherford Cables for HL-LHC and FCC

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IOP : On the mechanics of MQXFB—the low-beta quadrupole for the HL-LHC

The Large Hadron Collider luminosity upgrade requires the replacement of standard 8.3 T Nb-Ti main dipole magnets with pairs of shorter 11 T Nb3Sn dipole magnets. After the manufacturing and testing of several 2 m-long 11 T models, the full-length 11 T magnet series production is now ongoing. As a result of a degraded quench performance in several short models, attributed to excessive stress in the coils’ midplanes, an upper hard limit for the coils’ pre-stress was set to avoid any conductor degradation. With the aim of further investigating the influence of a lower pre-stress, an additional double-aperture short model was manufactured. The first aperture was assembled with the standard pre-stress target, in line with the series production. The second aperture was assembled with half of the standard pre-stress. Both apertures were then assembled into a 2-in-1 structure, but connected individually in order to power them independently to allow for comparison studies. Contrary to previously built 11 T magnets, the conductor type is also different as Powder-in-tube (PIT) cable was used, instead of standard Restacked-Rod-Process (RRP) cable. Additionally, the quench heaters for magnet protection were not impregnated as previously done, but placed on the outer radial surface of the coils, in agreement with the final decision for the 11 T series production. This paper describes the manufacturing and testing campaign results of this last 11 T short model.

Dariusz Pulikowski

Papers

Progress in the Development of the Nb 3 Sn MQXFB Quadrupole for the HiLumi Upgrade of the LHC

Testing Mechanical Behavior of Nb3Sn Rutherford Cable During Coil Winding

Windability Tests of Nb 3 Sn Rutherford Cables for HL-LHC and FCC

IOP : On the mechanics of MQXFB—the low-beta quadrupole for the HL-LHC

Pre-Load Studies on a 2-m Long Nb 3 Sn 11 T Model Magnet for the High Luminosity Upgrade of the LHC