The Local Helium Compound Transfer Lines for the Large Hadron Collider Cryogenic System

The cryogenic system for the Large Hadron Collider (LHC) under construction at CERN will include twelve new local helium transfer lines distributed among five LHC points in underground caverns. These lines, being manufactured and installed by industry, will connect the cold boxes of the 4.5‐K refrigerators and the 1.8‐K refrigeration units to the cryogenic interconnection boxes. The lines have a maximum of 30‐m length and may possess either small or large re‐distribution units to allow connection to the interface ports. Due to space restrictions the lines may have complex routings and require several elbowed sections.The lines consist of a vacuum jacket, a thermal shield and either three or four helium process pipes. Specific internal and external supporting and compensation systems were designed for each line to allow for thermal contraction of the process pipes (or vacuum jacket, in case of a break in the insulation vacuum) and to minimise the forces applied to the interface equipment. Whenever possible, flexible hoses were used instead of bellows to allow for thermal compensation of the process pipes. If necessary, compensation units were integrated in the vacuum jacket. The thermal design was performed to fulfil the specified heat‐load budget.This paper presents the main technical design choices for the lines together with their expected performance.The cryogenic system for the Large Hadron Collider (LHC) under construction at CERN will include twelve new local helium transfer lines distributed among five LHC points in underground caverns. These lines, being manufactured and installed by industry, will connect the cold boxes of the 4.5‐K refrigerators and the 1.8‐K refrigeration units to the cryogenic interconnection boxes. The lines have a maximum of 30‐m length and may possess either small or large re‐distribution units to allow connection to the interface ports. Due to space restrictions the lines may have complex routings and require several elbowed sections.The lines consist of a vacuum jacket, a thermal shield and either three or four helium process pipes. Specific internal and external supporting and compensation systems were designed for each line to allow for thermal contraction of the process pipes (or vacuum jacket, in case of a break in the insulation vacuum) and to minimise the forces applied to the interface equipment. Whenever possible...