Use Cases

We work hand-in-hand with CERN equipment owners to develop state-of-the-art designs based on their specifications, agreeing with the Groups, who maintain the final responsibility of the equipment, the main design choices.

Mechanical design of a new end cap structure for CMS

Overview:

As part of the CMS end cap High-Granularity Calorimeter(HGCAL) upgrade for the Long Shutdown (LS3) a new structure needs to be designed and built to host the new detector components offering enhanced resolution, timing, radiation tolerance when exposed to the new High-Luminosity Large Hadron Collider (HL-LHC) conditions.

Challenge:

The HL-LHC endcap must integrate delicate detector elements within tight envelopes while supporting ~220 t of self-weight and resisting strong electromagnetic forces. Large stainless-steel plates (5 m diameter, 60 mm thick) must maintain flatness below 1mm with total deformations of its 21 piled-up plates kept below 10 mm. Achieving this precision requires robust mechanical design and anticipation of the full chain from machining and metrology to assembly, transport, and underground installation

Solutions:

The cylindrical tapered endcap (Ø 2.5–5 m) is built from 21 plates made from stainless steel with low permeability, each split into three bolted sub-parts for transport and assembly. High-strength bolts (up to 600 MPa) combined with precision dowel pins provide slip-critical, preloaded joints with controlled shear transfer and repeatable alignment. Precision machining, strict QA, and laser tracker surveys ensure a common flatness plane across all seams. The structure withstands ~220 t self-weight and electromagnetic forces while keeping global deformation below 10 mm, guaranteeing stable long-term performance under HL-LHC conditions.

BENEFITS

Facilitates transport and handling by dividing the endcap into manageable sub-parts.

High-strength bolts and dowel pins ensure rigid, reliable joints that withstand ~220 t self-weight and electromagnetic forces.

Flatness tolerances are controlled through a design-to-manufacturing approach and verified by laser tracker metrology, keeping deformations below 1 mm over 5 m and ensuring proper insertion of the detector components.

Features for assembly tooling are embedded inside the design.

Strict material procurement specifications contain permeability values to reduce electromagnetic forces on the structure.

OUTCOME

This solution delivers a robust, precisely aligned endcap that protects detector components, ensures stable performance under HL-LHC conditions, and minimizes risks and downtime, strengthening CERN’s ability to achieve world-leading physics results.