Champagne for the cryogenics teams

Christmas has come early for the LHC as a complete sector of the cryogenic distribution line has been operating at 10 degrees Kelvin (-263°C) for the past two weeks, just a few degrees above the machine's nominal operating temperature.

The first section of the LHC cryogenic distribution line, an eighth of the accelerator, has been tested at a temperature of 10 kelvin (-263ºC) since end of November 2005.

The cryogenics teams will be able to celebrate the end of the year in style by cracking open the champagne down in the tunnel as the installation and testing of the cryogenic distribution line (QRL) goes from strength to strength. Back in September a pressurisation and cooling test was successfully performed on a 600-m stretch of the QRL (see Bulletin No. 40/2005 of 3 October 2005). Since 12 November, a complete sector of the LHC ring, between Points 1 and 8, has been undergoing tests. One sector represents an eighth of the LHC ring, more than three kilometres' worth of cryoline.

The procedure is identical to that used for the previous test. The QRL first underwent a pneumatic pressurisation test and was then flushed with helium at room temperature to remove all impurities before cooling began using one of the new 4.5 K refrigerators installed on the surface at Point 8 (see Bulletin No. 7/2004 of 9 February 2004).

Cooling itself began on 21 November. After three days the temperature had been lowered to 10 degrees Kelvin, or -263°C. Last week, the teams began checking the instrumentation. " We have thermometers, heaters and pressure sensors to commission and check at cryogenic temperature ", explains Germana Riddone, Head of the LHC Cryogenic Distribution Section (AT-ACR-CD) and QRL Project Engineer. The measurements to validate the thermal losses on the line began this week. The line will remain cold until the end of the year when a full operating report will be drawn up. These tests are being conducted in collaboration with the AT Department's Operation Cryogenics (AT-ACR-OP) and Instrumentation and Controls (AT-ACR-IN) Sections.

Meanwhile, installation of the cryoline in the other sectors of the LHC ring is continuing. Sector 4-5 is complete and a pressurisation test is scheduled later in December. Sector 3-4 is two-thirds of the way towards being installed, and work has begun in Sector 5-6. The next major step for the cryogenics teams will be the cooling tests with magnets.