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The LHC cryogenic system is based on a five-point feed scheme with eight refrigerators serving the eight sectors of the LHC machine: the LHC-points 1.8, 2, 4, 6 and 8:

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• Extra information

·         Useful Information:

§         Rapid-Info

§         Piquet CERN-ALLS

§         Info TCR

·         Operation Tools (restricted access)

·         Naming Conventions

·         Projects:

§         GTPM Cryo LHC - Website

• The Cryogenic Functional Analysis Working Group

·         Recent publications:

§         Large cryogenic infrastructure for LHC superconducting magnet and cryogenic component tests: layout, commissioning and operational experience

§         Experimental validation and operation of the LHC Test String 2 cryogenic system

§         Operational experience on cryogenic systems for large-scale accelerators at CERN

§         Cooling down of a LHC Sector - LHC days 2003 presentation

• General Information:

In all, LHC cryogenics will need 40,000 leak-tight pipe junctions, 12 million liters of liquid nitrogen will be vaporized during the initial cool down of 31,000 tons of material and the total inventory of liquid helium will be 700,000 liters.

It will use super fluid helium, which has unusually efficient heat transfer properties, allowing kilowatts of refrigeration to be transported over more than a kilometer with a temperature drop of less than 0.1 K.

LHC superconducting magnets will sit in a 1.9 K bath of super fluid helium at atmospheric pressure (sub cooled liquid or pressurized helium II). This bath will be cooled by low pressure liquid helium (saturated helium II) flowing in heat exchanger tubes threaded along the string of magnets. The reliability and efficacy of this sophisticated cryoloop are key factors in achieving the required magnet performance.  The LHC cryogenic system is very large as well as very cold. Refrigeration power equivalent to over 140 kW at 4.5 K is distributed around the 27 km ring. It is based on a five-point feed scheme with eight refrigerators serving the eight sectors of the LHC machine: the LHC-points 1.8, 2, 4, 6 and 8.

    

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The cryogenic installations are composed of different equipments to feed 2 sectors with 4.5K helium and super fluid helium at 1.9K. On the LHC-points 4,6 and 8 the following configuration is present: for each sector there is a 18kW refrigerator at 4.5K, a refrigeration unit at 1.9K, a transfer line and an interconnection box.

 

The  production sites 1.8 and 2 are different from the others. Both sites are feeding only one sector. They have only one 18kW refrigerator at 4.5K and one refrigeration unit at 1.9K. The LHC-point 1.8 is for the moment dedicated for testing the magnets before installation into the tunnel.

 

Each installed equipment is going through a period of acceptance tests and then passed on to the exploitation. Most of the cryogenic installations are still in the installation and testing period.

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