The latest from the LHC

The last collimator being installed at point 8 on 23 June.

All repairs in Sector 3-4, the sector damaged during the incident last September, have been completed and the sector has been closed up. After the last electrical interconnection was brazed, the final ‘W bellow’ - the large accordion-shaped sleeve that covers the interconnections between two magnets - was closed on 23 June. The teams have now started to pump the air out in order to leak-test the insulation vacuum. Once all the vacuum tests and electrical tests have been completed the sector will be ready to start the cool-down process.

Sector 3-4 was closely followed by Sector 5-6, where interconnections were completely closed two days later. All the helium pressure release ports were installed in the sector back in April, but the sector remained open so that tests and repairs could be made on the copper stabilized busbar interconnections: in total ten busbar interconnections were repaired.

Sector 4-5 is now at room temperature and tests are currently being carried out on the superconducting busbars (see previous update). While the sector is warm, the teams are taking the opportunity to perform some other consolidation work, such as installing pressure release ports and additional insulation in a connection cryostat. The RF ball test was performed successfully, and showed no defective Plug-In Modules (PIMs) - a significant result since this is the first sector to have been cooled and re-warmed after having had defective PIMs replaced.

Sector 1-2, which was closed two weeks ago, has now been validated by vacuum and electrical checks and is ready to start cool down to 1.9 Kelvin.

The final collimator

The final collimator has been installed ready for the LHC restart (phase 1 of the LHC collimator project). The collimators are installed around the LHC ring and the transfer lines to absorb ‘stray’ particles that have spread out, forming a halo around the beam. It is important to absorb this halo to protect the rest of the machine from damage, in particular the superconducting magnets, where any slight heating by stray particles could cause a magnet quench. The one-metre long collimators absorb the particles in the halo by closing a set of ‘jaws’ of various materials around the beam; the most robust collimators use fibre-reinforced graphite.

Before the start-up last year, 88 collimators were installed. The unforeseen shutdown caused by the incident in Sector 3-4 allowed the collimator team to continue with the final 20 collimators necessary to maximize the LHC intensity and luminosity reach with the phase 1 collimation system. This marks the end of six-and-a-half years of hard work since the project began.

Work is continuing on the collimator project to install additional collimators ready for the LHC upgrade (phase 2), which will have higher intensity beams.

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