Second LHC transfer line passes beam test with flying colours

20 November 2007

Three years after the initial commissioning of the SPS-to-LHC transfer line, TI 8, the second transfer line, TI 2, has passed its first test with beam. Just as for TI 8 in October 2004, a low-intensity proton beam travelled down the entire new line at the first attempt.


The two LHC injection lines have a combined length of 5.6 km and comprise around 700 warm (normally conducting) magnets. While around 70 magnets were recuperated from earlier installations at CERN, the majority were produced by the Budker Institute for Nuclear Physics in Novosibirsk, as part of Russia’s contribution to the LHC project.

TI 2 leads from the extraction in long straight section 6 (LSS6) of the SPS to the injection point on the LHC for clockwise beam, which is near the interaction region for the ALICE experiment at Point 2. To transfer beam to the LHC, LSS6 has a new fast extraction, which underwent commissioning in 2006 and further testing in 2007. Following the extraction, the beam passes for 150 m through the TT60 line, formerly used for transfer to the West Area, before entering the TI 2 line in its purpose-built 3 m diameter tunnel.

Installation of the TI 2 beamline started at the beginning of 2005 in the upstream part of the new tunnel, followed by initial hardware commissioning that summer. However, as the downstream part of the TI 2 tunnel served as a transport path for the main LHC magnets, it had to remain free of beamline elements until the LHC magnets were all in place. With the descent of the last magnet in April 2007, installation of the TI 2 line resumed, reaching completion at the beginning of August. This was followed by some eight weeks of hardware commissioning for the whole beamline.

The beam test, which took place over a 22 hour period, started early on 28 October. The commissioning team first prepared a single-bunch beam of 5 × 109 protons and set the TI 2 line to the SPS energy before tuning the SPS extraction. Then, when they retracted the beam dump near the extraction, the beam travelled without any steering straight through the 2.7 km of beamline components to the temporary dump installed near the end of the TI 2 tunnel. During the time remaining, the team made a range of basic measurements; after an initial analysis the basic parameters are looking good, indicating that there are no major errors in the line.

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