Powering tests finished at the end of the first week of March, opening the way for 4 TeV operations this year. The beam was back in the machine on Wednesday 14 March.
Magnet powering tests were followed by the machine checkout phase. Here the operations team, in collaboration with the equipment groups, performs a sequence of tests to ensure the LHC is ready for beam. The tests include driving all the LHC systems – beam dump, injection, collimation, RF, power converters, magnet circuits, vacuum, interlocks, controls, timing and synchronization – through the operational cycle. The “checkout phase” is really a massive debugging exercise, which is performed with the objective of ensuring the proper functioning of the whole machine and the protection systems.
During the checkout phase, work continued in the LHC tunnel during the day. The vacuum group prepared sectors that were open during the technical stop for beam. The vacuum group finished their work on Friday 9 March and the LHC was closed for full-scale tests over the weekend. These included taking beam down the transfer lines running from the SPS to the LHC. By the evening of Wednesday 14 March the LHC was in good shape and took beam again. Things went pretty smoothly and circulating beams were rapidly re-established. The RF group worked overnight to time in their system and by the morning both beams were available for optics measurements. The next 3 weeks will be devoted to an intensive (re)-commissioning campaign. First stable beams at 4 TeV should be declared sometime in the first week of April.