He II heat exchanger test unit for the LHC inner triplet
The Inner Triplet Heat Exchanger Test Unit (IT-HXTU) is a 30-m long thermal model designed at Fermilab, built in US industry, fully automated and tested at CERN as part of the US LHC program to develop the LHC Interaction Region quadrupole system. The cooling scheme of the IT-HXTU is based on heat exchange between stagnant pressurized He II in the magnet cold mass and saturated He II (two-phase) flowing in a heat exchanger located outside of and parallel to the cold mass. The purposes of this test are, among others, to validate the proposed cooling scheme and to define an optimal control strategy to be implemented in the future LHC accelerator. This paper discusses the results for the heat exchanger test runs and emphasizes the thermal and hydraulic behavior of He II for the inner triplet cooling scheme.
Cryogenic System and Cryostat Design for the LHC IR Quadrupole Magnets
The LHC interaction region (IR) inner triplet cryostats are under development at Fermilab. The inner triplet consists of four 70 mm aperture superconducting quadrupole magnets manufactured at Fermilab and KEK. These magnets are cooled with pressurized static superfluid helium at 1.9 K which transports the heat to saturated 1.8 K He II via a He II heat exchanger. This paper discusses the requirements for the inner triplet cryostat, development of the cryogenic system, and He II heat exchanger arrangement. Cooldown and quench pressure issues with the external He II heat exchanger are also discussed.
Superfluid helium cryogenics for the large hadron collider project at CERN
Abstract The Large Hadron Collider (LHC) at CERN will be the next research instrument of high-energy physics. Colliding protons at 14 TeV center-of-mass energy and high luminosity, it will probe the structure of matter down to an unprecedentedly fine scale, thus allowing to reproduce in the laboratory phenomena which occurred in the very early universe. On the technological side, the LHC makes use of high-field superconducting magnets for guidance and focusing of the particle beams around the 26.7 km circumference of the machine, to be installed in the existing LEP tunnel. The nominal bending field of 8.65 T is produced in some 1300 twin-aperture dipoles, wound with small-filament Nb Ti conductor, and operated below 1.9 K in static baths of pressurized helium II, thus taking advantage of its specific properties as cooling fluid. We present the main technical challenges of the LHC cryogenic system, and review the actions of development and the preparatory work in progress.