The High-Luminosity Large Hadron Collider project at CERN will increase the accelerator luminosity to allow experiments to gather more data and observe rare events after 2025. Swiss metal forging company Imbach is using an integral open-die forging and CNC controlled ring rolling process to manufacture massive cylindrical aluminium alloy sleeves  enclosing the high-performance superconducting magnets that are a key part of the upgrade.

The High-Luminosity Large Hadron Collider project at CERN, Geneva will enhance the performance of the flagship Large Hadron Collider accelerator to increase the potential for discoveries after 2025. The project will multiply the accelerator luminosity by a factor of five to allow experiments to gather more data and observe rare events. The project will also take the opportunity to replace many critical components of the accelerator which are reaching the end of their working life. An integral part of the upgrade are ten new Nb₃Sn technology based superconducting magnets measuring 7 meters in length and providing peak magnetic fields of 11  tesla. Each magnet will be cooled to an operating temperature of 1.9 Kelvin (-271 ºC).

To withstand the significant mechanical stresses from cooling and the strong magnetic fields and high electrical currents during operation, each magnet is held together by cylindrical aluminium sleeves manufactured by Imbach. In order to avoid any distortions of the magnetic field, very narrow tolerances have to be achieved for the machined cylindrical sleeves.

Final cross section of the magnet with beam path

Starting from traditionnal forging technics 

Imbach manufactured the magnet sleeves from a high-strength aluminium-zinc alloy. The forging blanks are manufactured by  traditional open die  forging using a hydraulic press.. The initial ring geometry is made by punching with a mandrel and stamping of a hole into the workpiece. CNC assisted ring rolling allows a constant reproducibility and usage of less additional material. Each cylindrical magnet sleeve is around 7 meters long, 0.63 meters in diameter and weighs around 200 kilograms.

Forging over mandrel with control of axial and radial reduction

Computer assisted open die forging with 3000 T of pressing force

The processes used by Imbach mean that the magnet sleeves can meet CERN’s exacting technical requirements of having no welding joints, optimum metallic grain flow, fine surfaces, high dimensional accuracy and outstanding mechanical properties. For CERN, Imbach plays a crucial role in meeting stringent quality requirements and successfully implementing new projects and the just-in-time delivery of the components helps in meeting the tight schedule for the project.