The Large Hadron Collider (LHC)1 currently under construction at CERN will make use of superconducting magnets operating in superfluid helium below 2 K. The cryogenic distribution scheme for each of the eight sectors, individually served by a refrigeration plant, is based on a separate Cryogenic Distribution Line (QRL) feeding helium at different temperatures and pressures to the elementary cooling loops. The QRL comprises two supply headers and three return headers including a sub-atmospheric one. Low heat inleak to all temperature levels is essential for the overall LHC cryogenic performance. With an overall length of 25.6 km the QRL has a very critical cost-to-performance ratio. Therefore, following an in-house feasibility study, CERN adjudicated in autumn 1998 three industrial contracts in parallel for the supply of Pre-Series Test Cells (~ 112 m) of the QRL, which will be tested at CERN in 2000. Installation of the QRL for LHC is scheduled from 2002 to mid 2004. This paper will present the general layout, the functional requirements as well as some aspects of the in-house conceptual design. ABSTRACTThe Large Hadron Collider (LHC) 1 currently under construction at CERN will make use of superconducting magnets operating in superfluid helium below 2 K. The cryogenic distribution scheme for each of the eight sectors, individually served by a refrigeration plant, is based on a separate Cryogenic Distribution Line (QRL) feeding helium at different temperatures and pressures to the elementary cooling loops. The QRL comprises two supply headers and three return headers including a sub-atmospheric one. Low heat inleak to all temperature levels is essential for the overall LHC cryogenic performance. With an overall length of 25.6 km the QRL has a very critical cost-to-performance ratio. Therefore, following an in-house feasibility study, CERN adjudicated in autumn 1998 three industrial contracts in parallel for the supply of Pre-Series Test Cells (~ 112 m) of the QRL, which will be tested at CERN in 2000. Installation of the QRL for LHC is scheduled from 2002 to mid 2004. This paper will present the general layout, the functional requirements as well as some aspects of the in-house conceptual design.

delivered by L'Air Liquide (France) and Cryogenmash (Russia) will also be compared. Performances of the liquid helium distribution systems tests of the four plants will be described, and their main features will be operating hours. Processes, construction, commissioning and acceptance years, and two of them have already accumulated a considerable number of Linde, Switzerland/ Germany). These plants have been installed in the past ordered in 1991, two from L'Air Liquide (France), two from Sulzer (now refrigeration power for the cavities, four 12(l8)kW/4.5 K cryoplants were

The Large Hadron Collider (LHC), currently under construction at CERN, will make use of superconducting magnets operating in superfluid helium below 2 K. The reference cryogenic distribution scheme was based, in each 3.3 km sector served by a cryogenic plant, on a separate cryogenic distribution line which feeds elementary cooling loops corresponding to the length of a half-cell (53 m). In order to decrease the number of active components, cryogenic modules and jumper connections between distribution line and magnet strings a simplified cryogenic scheme is now implemented, based on cooling loops corresponding to the length of a full-cell (107 m) and compatible with the LHC requirements. Performance and redundancy limitations are discussed with respect to the previous scheme and balanced against potential cost savings. ABSTRACTThe Large Hadron Collider (LHC), currently under construction at CERN, will make use of superconducting magnets operating in superfluid helium below 2 K. The reference cryogenic distribution scheme was based, in each 3.3 km sector served by a cryogenic plant, on a separate cryogenic distribution line which feeds elementary cooling loops corresponding to the length of a half-cell (53 m). In order to decrease the number of active components, cryogenic modules and jumper connections between distribution line and magnet strings a simplified cryogenic scheme is now implemented, based on cooling loops corresponding to the length of a full-cell (107 m) and compatible with the LHC requirements. Performance and redundancy limitations are discussed with respect to the previous scheme and balanced against potential cost savings.

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