First magnet operation on the cryogenic test stand Gersemi at FREIA

Abstract

The Gersemi cryogenic test bench, installed at FREIA laboratory at Uppsala University, was used for the first time in 2021 to power a superconducting magnet. As part of the HL-LHC program, this cryostat offers an operating temperature between 4.2K and 1.9K. Its satellite equipment such as power converters and the acquisition system allow two superconducting magnet coils to be powered up to 2 kA and provide magnet protection through a robust quench detection and two energy extraction units. This report describes Gersemi's first cryogenic operational experiment and the safety strategy to ensure magnet integrity during operation.

Training-free performance of the wax-impregnated SuShi septum magnet

“…The Sushi magnet was tested at 4.2 K in the vertical cryostat Gersemi [35] of the FREIA (Facility for Research Instrumentation and Accelerators, Uppsala University, SE) laboratory. The cryostat is equipped with a dedicated magnet insert containing a lambda-plate, which allows operation between 4.2 K and 1.9 K maintaining the liquid helium bath at atmospheric pressure [36], providing a maximum current of 2 kA DC with 4 hybrid current leads (copper + NbTi).…”

“…The voltage tap wires (connected to the splices within the magnet and to different spots along the leads) were connected to the 'Potential Aimant' (PotAim) cards of the quench protection system to monitor direct or differential voltages and trigger the quench protection protocol if necessary [36]. Several circuits were used to avoid being blind to symmetric quenches and for redundancy.…”