Long, Bellows-Free Vertical Helium Transfer Lines for the LHC Cryogenic System

The cryogenic system for the Large Hadron Collider (LHC) under construction at CERN will include four new vertical helium transfer lines connecting the new helium refrigerators to the underground areas. These four transfer lines will be installed between a refrigerator on the surface and an interconnection box located 80 m to 145 m underground. They consist of a vacuum jacket, a thermal screen and four internal helium pipes. Due to space and accessibility limitations, the lines have been specified without bellows or bends of any kind in the long vertical part; the thermal contractions must be compensated at the surface only. The displacement due to these contractions amounts to more than 35 cm in one case, and all four internal pipes, as well as the thermal screen, must be able to contract and expand independently. The lines will be built and installed by a consortium of Linde AG and Babcock Noell Nuclear GmbH. Their technical design choices are presented together with expected performance

Measured Performance of Four New 18 [email protected] K Helium Refrigerators for the LHC Cryogenic System

The cryogenic system for the Large Hadron Collider (LHC) under construction at CERN will include four new 4.5 K-helium refrigerators, to cover part of the cooling needs of the LHC at the 4.5-20 K and 50-75 K levels. Two refrigerators are delivered by Air Liquide, France, and two by Linde Kryotechnik, Switzerland. During the last three years, all four refrigerators have been installed and commissioned at four different points along the LHC. The specified requirements of the refrigerators are presented, with special focus on the capacities at the various temperature levels. The capacities of the refrigerators were measured using a dedicated test cryostat, and the measured performance for all four installations is presented, and compared to the guaranteed performance in the original proposal of the suppliers. Finally, the process design of the two supplies is compared, and their differences and similarities briefly analysed

Commissioning of the LHC Cryogenic System: Subsystems Cold Commissioning in Preparation of Full Sector Tests

The cryogenic system for the Large Hadron Collider accelerator is presently in its final phase of installation and commissioning at nominal operating temperatures. The refrigeration capacity for the LHC will be produced using eight large cryogenic plants installed on five technical sites and distributed around the 26.7-km circumference ring located in a deep underground tunnel. The status of the cryogenic system commissioning is presented together with the experience gained in operating and commissioning it