The success of the 11-Tesla project and its potential beyond particle physics

On 7 March, the 1-metre-long single-aperture dipole model magnet under testing at Fermilab reached a current of 12.54 kA corresponding to a bore field of 11.5 Tesla, thus surpassing the goal set for the 11 T dipole project.


Computer generated model of the FNAL 1 metre 11 T dipole model magnet and a pair of CERN coils. Image: courtesy of Don Mitchell, FNAL.

The 11-Tesla dipole project originated from a proposal made by High Luminosity LHC project coordinator, Lucio Rossi, in September 2010. To cope with the increasing amount of debris hitting the magnets when increasing the number of collisions produced by the LHC, he suggested replacing a few 8-Tesla dipole magnets in the LHC tunnel with shorter, stronger 11-Tesla magnets in order to create enough space to install additional collimators. The only way to achieve this goal is to use advanced niobium-tin technology.

Rossi’s proposal aligned well with the goals of Fermilab’s High-Field Magnet R&D programme, which aims to develop collared magnets with fields in excess of 10 Tesla for use in future machines such as the Muon Collider or the Very Large Hadron Collider. The two laboratories quickly established a collaborative effort under the umbrella of the High Luminosity LHC project and jointly designed and developed the magnet concept based on collared cos-theta coils. The goal of the on-going first phase of the 11 T dipole model programme is to demonstrate the quench performance with short (1-2 m) single-aperture magnets. The second phase will address the “accelerator-quality” design in twin-aperture configuration, first with 1-2 m model magnets then with a full 5.5-m-long prototype dipole compatible with the LHC’s main systems.

The magnet is the second single-aperture model magnet constructed at Fermilab. An important issue concerning long-term stability needs to be addressed by a third prototype, which is under construction by the Fermilab team. However, this recent test shows accelerator quality potential: for example this was the first accelerator magnet with a cored cable (core drastically reduces eddy current during ramping, thus reducing ramp dependence) and a relatively small filament size (36 mm).  

The design and manufacturing of the first 2-m-long model magnet is also progressing well at CERN. While relying on the coil technology developed at Fermilab, the CERN team is striving to accommodate interesting alternative design features: cable insulation made by braiding S2-glass on mica-glass tape, inter-layer quench heaters, and a new collaring concept for pre-loading the brittle niobium-tin coils.  “We are currently in the final stage of commissioning the coil production tooling and, provided the results of the first practice coils are satisfactory, we expect to test our first single-aperture magnet around September this year,” says Mikko Karppinen, 11 T project leader at CERN.

Exceeding the 10-Tesla barrier with the relatively new niobium-tin technology can allow scientists to plan hadron colliders that could reach 100 TeV centre-of-mass energies, about seven times more than the design energy of the LHC.

Another advantage is that the niobium-tin technology will have applications beyond particle physics as well. As Giorgio Apollinari, head of Femilab’s Technical Division says, “Hospitals will rely on niobium-tin-equipped MRI systems, which will provide more detailed images due to the higher magnetic fields achieved by these magnets, leading to improved medical diagnoses.”

To read the original Fermilab article, click here.

by CERN Bulletin