Experimental Validation and Operation of the LHC Test String 2 Cryogenic System

The LHC Test String 2 is a 107-m long superconducting magnet string representing a full-cell of the LHC machine. It was designed and commissioned at CERN in order to validate the final design choices and to investigate the collective behavior and operation modes of the LHC machine systems. It has been commissioned and operated since April 2001 and has accumulated more than 8000 hours at its nominal operating temperature of 1.9 K under machine-like conditions. We report on the experimental validation of the supercritical and superfluid helium cooling loops, quench propagation and recovery, heat loads, as well as on investigation of operational performances, advanced control techniques, process control, instrumentation and long term behavior under electrical and thermal cycling.