Project overview
The Cluster D Vertical Cryostat is a deep-bore cryogenic facility designed for the vertical testing of large superconducting magnets. The system enables low-temperature performance testing and magnetic field measurements under controlled operating conditions, before the final integration of the magnets into their cryogenic vessels.
The project is part of the SM18 Test Facility at CERN, an infrastructure dedicated to the testing of superconducting magnets for particle accelerators and to the activities related to the High-Luminosity LHC upgrade. It required the development of a complex system combining mechanical precision, thermal control and operational reliability in a highly advanced scientific environment.
Alca Technology scope
Alca Technology managed the design, manufacturing, assembly, testing and operational validation of the cryostat, with a specific focus on reducing thermal losses and optimizing cryogenic sealing performance.
Technical challenge
The system had to operate under extremely demanding cryogenic conditions, ensuring thermal stability, mechanical reliability and limited liquid helium losses.
The cryostat has an operating depth of approximately 9.3 meters, a useful diameter of approximately 0.6 meters and the capacity to accommodate magnets weighing up to 8 tons. The cryogenic configuration includes a dual-bath system, with saturated liquid helium at 4.5 K in the upper section and a superfluid helium bath at 1.9 K in the lower chamber.
In this context, thermal loss management was one of the main technical challenges. Even minor geometric deviations or inefficiencies in the sealing area could generate significant liquid helium losses, increasing operating costs and reducing the overall efficiency of the facility.
Alca Technology solution
To meet the project requirements, Alca Technology developed a design and manufacturing solution focused on minimizing thermal losses.
A key element of the solution was the cryostat internal sealing ring. To improve the component geometric quality and ensure greater precision during coupling, Alca Technology specified a dedicated mechanical machining process for the ring under tension. This approach allowed more effective control of the sealing surface flatness, reducing the risk of cryogenic losses and contributing to the overall efficiency of the system.
The maximum accepted flatness requirement for the ring was 1.4 mm. The solution implemented by Alca Technology achieved a final flatness of 0.4 mm, significantly improving the margin compared to the required specification.
Cryogenic architecture
The cryostat uses a Claudet bath configuration, with saturated liquid helium at 4.5 K in the upper section and cooling of the lower chamber through a superfluid helium bath at 1.9 K.
The thermal management system is supported by sub-cooled liquid-liquid heat exchangers, required to keep the superfluid bath stable. An actively cooled 50 K thermal shield also helps limit heat loads coming from the room-temperature neck and the magnet inserts.
This architecture enables superconducting magnets to be tested under conditions representative of real operation, ensuring high precision in both cryogenic and magnetic testing.
Results
The cryostat manufactured by Alca Technology demonstrated excellent operational performance, standing out for its limited thermal dispersion and efficient liquid helium management.
The improvement in the flatness of the sealing ring, from a maximum accepted tolerance of 1.4 mm to an achieved value of 0.4 mm, contributed significantly to the reduction of helium losses. This result has a direct impact on the operational sustainability of the facility, considering the high cost of liquid helium and the need to ensure continuity in cryogenic testing activities.
Compared with an alternative solution manufactured by another supplier, the system developed by Alca Technology proved to be more efficient in operation and less affected by issues related to cryogenic losses. The Alca Technology cryostat is currently the solution in actual use, thanks to its higher performance and lower management costs.
Key strengths
The project confirms Alca Technology ability to manage complex cryogenic systems throughout the entire development cycle, from design and manufacturing to testing and operational validation. The main strengths of the project include high-precision mechanical machining, a strong focus on reducing thermal losses, expertise in liquid helium management and the ability to manufacture special systems for high-technology research environments.
