Document information
Tags/Project: GERSEMI-wiki
| Metadata Field | Document Information |
|---|---|
| Status | Under Review |
| Created | 2026-06-24 |
| Last Updated | 2026-09-29 |
| Author | Davide Cuneo |
| Rev. # | 1.3 |
| Reviewers | Davide |
About the document
This document provides a description of the vessels that compose the GERSEMI cryostat.
Vacuum Vessel Structural Design and Shielding
The primary external container of the GERSEMI vertical cryostat is a vacuum vessel manufactured from 316L stainless steel, featuring an external diameter of 1.8 m and an overall height of 4.7 m. Mechanically, the vacuum vessel is suspended inside the underground pit infrastructure by three dedicated side supports. This assembly acts as the primary insulating boundary, housing the internal process components and the incoming cryogens routing from the auxiliary valve box through the side interface.
To regulate fluid distribution based on the active testing configuration, a network of cryogenic valves is integrated directly inside the vacuum vessel structure. This centralized placement minimizes parasitic heat leaks and simplifies the routing to the insert equipment. Radiative heat transfer within the vacuum vessel is intercepted by independent aluminum thermal shields actively cooled via liquid nitrogen (LN2) circulation. When operating in cavity testing configurations utilizing the vacuum insert, this LN2 shield circuit is also extended to cool the insert boundaries.
Pressure Vessel Geometry and Stepped Configuration
To accommodate the multi-purpose requirements of the facility, an internal container, referred to interchangeably as the pressure vessel or cold vesse, is housed concentrically within the vacuum vessel to function as the liquid helium storage tank for both the bath and lambda-plate inserts. Due to the dense integration of the internal cryogenic valve networks inside the cryostat envelope, the pressure vessel is mounted in an off-center (eccentric) position. Structurally, the pressure vessel is fastened directly to, and suspended from, the main top flange of the vertical cryostat.
The pressure vessel is manufactured from stainless steel and features a stepped cylindrical geometry split into two primary operational sections across its length:
- Upper Section: Extends across the upper third of the vessel length with an internal diameter of 1.25 m.
- Lower Section: Extends across the lower two-thirds of the vessel length with an internal diameter of 1.1 m.
The physical seat that links the upper 1.25 m diameter section to the lower 1.1 m diameter section forms a structural transition zone designed to accommodate and seal the lambda plate assembly. This configuration establishes the isolated double-bath regime required for testing superconducting magnets in pressurized superfluid helium. Because of the mechanical stresses associated with managing a pressurized helium bath during magnet testing, the container is classified as a Category III pressure vessel under standard regulatory frameworks.
Feedback
Found an error or something outdated in this note? Please contact Davide Cuneo (davide.cuneo@physics.uu.se).